book of abstracts posters a

POSTER SESSION I

8TH HELLENIC POLYMER SOCIETY SYMPOSIUM HERSONISSOS CRETE, 24 – 29 OCTOBER, 2010

86

PI-1: RADIATION GRAFTING OF THERMOCONTROLLED POLYMER ONTO POLYPROPYLENE FILMS

JUSTYNA KOMASA, SLAWOMIR KADLUBOWSKI, PIOTR ULANSKI, JANUSZ M. ROSIAK

Institute of Applied Radiation Chemistry, Technical University of Lodz, Wroblewskiego 15, 93-590 Lodz, Poland- [email protected]

Burn wounds are one of the most frequently occurring injuries. This kind of wound is a serious problem, not only because of its high happening frequency, but also due to the complications arising during its healing. Many conventional treatments of burn wounds are costly, slow and not very effective. Nowadays we can observe a fast progress of knowledge about processes occurring in wound and ways of healing it. Skin grafts are considered to be one of the best solutions; however, cell culture procedures used to obtain large surface grafts have still to be optimized. A persisting problem is how to detach the grown skin sheet from the substrate without causing excessive damage to the product. One of possible solutions is to use substrates with thermosensitive surfaces. The latter are currently recognized as valuable new materials with novel properties relevant for biomedical research fields such as artificial organs, biofunctional materials, drug delivery systems, separations of biomolecules and regenerative medicine. Thermoresponsive polymers are commonly used as surface modifiers. One of well known temperature – responsive polymer is poly(N-isopropylacrylamide) (PNIPAAm). PNIPAAm possesses a lower critical solution temperature (LCST) of 32°C in water. Below LCST the polymer is fully hydrated and soluble in water, but it collapses and becomes insoluble above the LCST. When PNIPAAm is grafted on the surface of a cell culture substrate, at 37°C the cells can adhere and grow easily on the surface, while lowering the temperature down to 25°C makes the surface hydrophilic, which should facilitate skin layer detachment without cell damage. The aim of this work is radiation grafting of poly(N-isopropylacrylamide) onto polypropylene (PP) films. This work is a part of the project aimed on developing new, innovative thermocontrolled scaffolds to be applied in culturing skin cell sheets. In the first step, radiation-induced grafting of NIPAAm onto PP films has been performed by pre-irradiation method. PP films were irradiated in air with 6MeV electrons from a linear accelerator (Linac ELU-6e, Elektronika Company) at a total absorbed radiation dose 50-150 kGy. The irradiated samples were placed in glass vessel containing 0,5-2 M aqueous solutions of NIPAAm, which were sealed, saturated with argon and heated to 70°C at different reaction times. The grafted samples were washed with water and dried. The films were characterised by gravimetric method, FTIR – ATR, contact angle measurements as well as SEM pictures. Results obtained so far indicate that PNIPAAm forms a permanent thermoresponsive layer at the surface of PP films while grafted by pre-irradiation method. Acknowledgements: This work was supported by European Union, European Regional Development Fund, project DERMOSTIM, UDA-POIG.01.03.01-00-088/08-0. The authors thank Ms. K. Blazniak for skilful technical assistance.


87

PI-2: STRUCTURAL CHANGES OF POLY(ETHYLENE TEREPHALATE) DURING PYROLYSIS AT LOW TEMPERATURES

ELENI ANOIKTOMATI, MARKELLA PISANIA, LOUKAS ZOUMPOULAKIS, JOHANNIS SIMITZIS

Laboratory Unit “Advanced and Composite Materials”, Department III “Materials Science and Engineering”, School of Chemical Engineering, National Technical University of Athens,

9 Heroon Polytechniou str., Zografou Campus, 157 73, Athens (Greece) – [email protected]

Abstract Polyethylene terephalate (PET) is considered one of the most important technical plastics of the last decades. PET is basically used for manufacturing films, fibres1, containers2 and mostly as a packaging material. In view of its widespread and significant amounts, a side effect also occurs concerning the domestic wastes. The plastic content in the latter is about 7-9% w/w, whereas the PET wastes constitute a remarkable portion. The primary recycling, consisting of collection, separation and post-transportation of wastes, is necessary for all solid wastes. Secondary or mechanical recycling reuses polymer wastes to produce low quality products, via melting and solution of polymers. A mixture of domestic wastes cannot be recycled by solvent or melt processes, because polymer mixtures as melts or solutions, even in the same solvent, are not compatible. The tertiary recycling, especially hydrolysis, glycolysis and methanolysis, is proven to be suitable to manage PET wastes, however as pure PET wastes. Pyrolysis (quaternary or thermal recycling) seems to be the best recycling solution for plastic mixture wastes.

The aim of this work is to study the structural changes of a common polymer, commercial PET, during its pyrolysis at low temperatures. The pyrolysis of PET took place at 350 or 430 oC for different residence times, in a tubular oven (Table 1) under nitrogen flow. The oven includes six zones, each one having its own temperature controller and thermocouple to monitor the temperature. One criterion to compare the pyrolysis behaviour for different polymers is their composition rate at 350 oC. Furthermore, it is known that the pyrolysis of PET from waste drink bottles exhibits weight loss (70-80%) occurring at temperature range of about 380 -515 οC3. Therefore, a second temperature at 430 oC (about at the middle of this range) is chosen in order to retain the solid residue its polymeric character. The structure of the pyrolysis solid residues was examined by Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Diffraction (XRD). The defined thermal treatment conditions of PET are presented in Table 1 which contains also the corresponding weight loss, the decomposition rate and the crystallinity of the solid residues. By considering the time of 10 min as the minimum time to have steady-state conditions in the oven, then the index v350 (% weight loss per minute at 350 oC) is 0.12% / min and that at 430 oC is 6.2% / min. By comparing the weight losses and the decomposition indexes at 350 and 430 oC, it is concluded that the main decomposition of PET takes place above 350 oC. The initial PET was introduced into the oven as grains and after the pyrolysis at 350 oC, its shape was as plate indicating that it has been melted during this thermal treatment. The amorphous state of PET at 350 oC for 10 min indicates that it has been not enough annealed under these conditions, in opposite to that at 350 oC for 30 min. The same crystallinity exhibits the PET pyrolyzed at 430oC for 10min. The most characteristic peaks, of the FTIR spectra of raw PET and pyrolyzed PET, are those with wavenumber at 2980-2950 cm-1 (due to stretching vibrations, -CH2, -CH3), 1736-1726 cm-1 (due to carbonyl group, >C=Ο), 1330-1200 cm-1 (due to esteric bond, Csp3-O) and 750 cm-1 (-CH, due to deformation vibrations “out of plane” 3 or 4 Η on the aromatic ring). Table 1. Pyrolysis parameters, weight loss and crystallinity of PET samples.

CODE Pyrolysis parameters Weight loss

(%) Crystallinity

(%) Temperature (oC) Time (min) 350 430 10 30

PET - - - - - 85 PET 350-10 - - 1.2 0 PET 350-30 - - 1.2 72 PET 430-10 - - 62 72 PET 430-30 - - 80 -

1 P. Santos, S.H. Pezzin, J. Mater. Process. Technol., 143-144 (2003), 517 2 F. Awaja, D. Pavel, Eur. Polym, 41 (2005), 2097 3 Β. Saha, A.K. Ghoshal, Chemical Engineering Journal, 111 (2005), 39


88

PI-3: COMPOSITE MATERIALS BASED ON NOVOLAC RESIN, CARBON NANOTUBES AND ORGANIC BIOMASS AS PRECURSORS FOR CARBONACEOUS

MATERIALS

ANASTASIA PIKASI, MARKELLA PISANIA, SOPHIA KARAMANOU, PANTELITSA GEORGIOU, LOUKAS ZOUMPOULAKIS, JOHANNIS SIMITZIS



Abstract Composites of carbon nanotubes (CNTs) in polymeric matrices have attracted considerable attention in the research and industrial communities due to their good electrical conductivity, high stiffness and high strength at relatively low CNTs content1. Multi – walled carbon nanotubes (MWNT) due to their extraordinary properties are ideal reinforcing materials in nanocomposites2. On the other hand, synthetic polymers like phenolic and epoxy resins in combination with natural polymers such as biomass have considerable application importance3. Biomass derived from agricultural byproducts can be used as fillers for composites, as it can be converted from low – value residue to high – value materials4. Carbonaceous materials with a high content of residue carbon can be used as precursor in a large number of applications such as adsorbents, electrodes etc3,5,6. The aim of this work is the manufacture of composites based on novolac resin, carbon nanotubes and organic biomass as precursors for carbonaceous materials. The composites were fabricated by mixing novolac resin (80, 60, 40% w/w) with hexamethylenetetramine (“hexa”) as curing agent and olive stones biomass (as grains with diameter less than 300 μm) in corresponding proportions. Carbon nanotubes were added as filler in a low content (5% w/w). The mixture was placed in proper mould in the form of disk (thickness 5 mm, diameter 20 mm) and cured by heating at 170 ºC for 30 min. The cured specimens were pyrolyzed under N2 atmosphere with a heating rate of 10 ºC / min up to 1000 ºC. The weight loss of the specimens and their shrinkage during pyrolysis were determined. The electrical conductivity σ of the carbonized solid materials was determined with the two probe method. The defined composition of precursor composites with or without carbon nanotubes and the electrical conductivity of the corresponding carbonaceous materials are presented in Table 1. Carbonaceous materials which have been pyrolyzed at 1000 ºC, derived from composite with the proportion of 80% w/w novolac, 20% w/w olive stones biomass and 5% w/w CNTs exhibit the highest value of electrical conductivity σ = 6.39x10-1 S/cm. The carbonaceous materials were characterized by X-Ray Diffraction (XRD) and their morphology was examined by Scanning Electron Microscopy (SEM). Table 1: Defined composition of precursor composites and electrical conductivity of carbonaceous materials

Acknowledgements: Financial support for this research was provided by NTUA in the frame of PEVE 2009 (Program for Basic Research) 1 Petra Potschke, Arup R. Bhattacharyya, Andreas Janke, European Polymer Journal 40, 2004, 137-148 2 Arash Montazeri, Alizera Khavandi, Jafar Javadpour, Abbas Tcharkhtchi, Materials and Design 31, 2010,

3383-3388 3 J. Simitzis, K. Karagiannis, L. Zoumpoulakis, Polymer international 38, 1995, 183-189 4 H. P. S. Abdul Khalil, P. Firoozian, I. O. Bakare, Hazizan Md. Akil, Ahmad Md. Noor, Materials and Design

31, 2010, 3419-3425 5 J. F. Gonzalez, S. Roman, J. M. Encinar, G. Martinez, J. Anal. Appl. Pyrolysis 85, 2009, 134-141 6 Anastasia Pikasi, Pantelitsa Georgiou, Johannis Simitzis, Key Engineering Materials, 446, 2010, 23-31

CODE OF COMPOSITE

MATRIX Novolac/Hexa

(% w/w)

OLIVE STONE BIOMASS(% w/w)

CARBON NANOTUBES (% w/w)

ELECTRICAL CONDUCTIVITY

(S/cm) N-B40 60 40 - 1.8 E-1

N-B20-CNT5 80 20 5 6.39 E-1 N-B40-CNT5 60 40 5 2.15 E-1 N-B60-CNT5 40 60 5 1.7 E-1


89

PI-4: MANUFACTURE OF COMPOSITE MATERIALS OF NOVOLAC RESIN - CARBON FIBRES - CARBON NANOTUBES AND THEIR MECHANICAL AND

ELECTRICAL PROPERTIES MARKELLA PISANIA, PANTELITSA GEORGIOU, LOUKAS ZOUMPOULAKIS, JOHANNIS SIMITZIS



Abstract The basic category of electrically conductive plastics is that of filled plastics with conductive fillers, such as metal particles1, carbon black, carbon fibers, etc2,3. These extrinsic conductive composites have been applied in numerous technological areas, including electromagnetic/ radio frequency interference shielding for electronic devices (e.g. computers and cellular housings), shelf-regulating heaters, overcurrent protection devices, photothermal optical recording, direction-finding antennas and chemical-detecting sensors that are used in electronic noses4. On the other hand, carbon nanotubes (CNTs) is a new material, which possess exceptional mechanical properties, superior thermal and electrical properties. Hence nanotubes can be ideal additives for structural and functional composites. New structural composite materials based on CNT reinforced thermoplastics or thermosets combine low density and strong mechanical properties, good thermal and electrical conductivity. A combination of these impressive properties enables a whole new variety of useful and beneficial applications 5,6. The aim of this work is the manufacture of multifunctional polymer-matrix composite materials combining proper mechanical properties with increased electrical conductivity. The methodology to achieve this target is the use of continuous carbon fibers in low volume percentage, in order to improve significantly the mechanical properties of the composite and simultaneously to retain as low as possible the cost of the composite material by avoiding a high content of the expensive carbon fibers. Novolac resin as matrix and carbon nanotubes in low proportion as conductive additive will be used in combination with carbon fibres. The continuous carbon fibers were pre-impregnated with novolac resin by immersing them in a solution of water / methanol containing a mixture of novolac –Hexa. After pre-impregnation, the solvent was removed by drying, the resin was partially cured and then the pre-impregnated carbon fibers were cut into laminates (prepregs). The amount of the continuous carbon fibers used in the composites (in the form of prepregs) was 15 % v/v. The novolac powder was mixed with hexamethylenetetramine, “hexa”, the certain amount of carbon nanotubes was added and all of them were mixed in order to produce a macroscopically homogenous powder. The carbon fiber laminates were placed unidirectionally in a proper mold by addition of the mixture of novolac/hexa – CNTs between the laminates and then the mold was heated and pressed in a thermopress apparatus. Then the mechanical and electrical properties of the composite specimens were measured. The results were discussed taking into consideration the influence of the manufacturing conditions of the composites. Acknowledgements: Financial support for this research was provided by NTUA in the frame of PEVE 2009 (Program for Basic Research) 1 Chung D.D.L., Carbon Fiber Composites, Butterworth-Heinemann: Boston, 1994 2 Huang, J.C., Adv Polym Tech, 21 (2002), 299 3 Fladin, L., Chang, A., Nazarenko, S., Hiltner, A., Baer, E., J Appl Polym Sci, 76 (2000), 894 4 Pinto, G.; Maaroufi, A.K., J Appl Polym Sci, 96 (2005), 201 5 Kim HM, Kim K, Lee CY, Joo J, Yoon HS, et al, Appl. Phys. Lett., 84 (2004), 589 6 Xu H, Anlage SM, Hu L, Gruner G, Appl. Phys. Lett., 90 (2007), 183119


90

PI-5: SYNTHESIS OF PMMA MAGNETIC MICROSPHERES VIA SUSPENSION POLYMERIZATION AND THEIR CHARACTERIZATION

WITH XRD, FTIR AND SEM SOTIRIA KARAGIOVANAKI, GEORGIOS MITSIS, JOHANNIS SIMITZIS, LOUKAS ZOUMPOULAKIS



Abstract

Magnetic materials are attracting significant fundamental and applied interest for a wide range of potential applications. In particular, magnetite (Fe3O4, 20nm in diameter) is an important kind of magnetic material having cubic inverse spinel structure which has been attracting increasing attention because of its wide use in magnetic recording1, ferrofluid2, catalyst3, and biomedical applications such as magnetic resonance imaging (MRI)4, bio-separation5, drug targeting6, and hyperthermia in cancer treatment7. Synthetic polymers such as PMMA, PCL, PVA, PLGA as well as natural polymers such as chitosan, collagen and starch polymers can be combined with magnetic nanoparticles because of their biocompatibility for such applications. The aim of this work is the manufacture of magnetic nanocomposites via suspension polymerization method, incorporating nano-Fe3O4 particles into PMMA matrix in order to obtain polymer magnetic microspheres with perspectives in biomedical and other applications. The monomer (MMA) and magnetic material (Fe3O4) are mixed together under vigorous stirring and follows suspension polymerization. The product was sequentially filtered through a range of sieves and spherical nanocomposites were obtained with grains of sizes ranging from 500 μm to 63 μm. The yield of polymerization was ∼ 60% and the corresponding polymer product contained 1.25% w/w Fe3O4. The nano-Fe3O4 particles and the magnetic polymer microspheres were characterized using techniques such as X-Ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) (Fig.1). The FTIR spectrum of PMMA-Fe3O4 nanocomposite shows the characteristic peaks at 580 cm-1 due to the Fe-O vibration of Fe3O4 and at 1737 cm-1 due to C=O stretching of the carbonyl group of PMMA as well as peaks near 3000 cm-1 characteristic of the C-H stretching of the aliphatic groups of the polymer.

Fig.1. SEM picture of magnetic PMMA microspheres.

1 A.H. Lu, E.L. Salabas, F. Schuth, Angew. Chem., Int. Ed. 46 (2007) 1222-1244 2 K. Raj, B. Moskowitz, R. Casciari, J. Magn. Mater. 149 (1995) 174-180 3L.M. Rossi, F.P. Silva, L.L.R. Vono, P.K. Kiyohara, E.L. Duarte, R. Itri, R. Landers, G.Machado, Green Chem. 9 (2007) 379-385 4 J.H. Lee, Y.W. Jun, S.I. Yeon, J.S. Shin, J. Cheon, Angew. Chem., Int. Ed. 45 (2006) 8160-8162 5 D.D. Shao, K.K. Xu, X.J. Song, J.H. Hu, W.L. Yang, C.C. Wang, J.Colloid Interface Sci. 336 (2009) 526-532 6X.Q. Yang, Y.H. Chen, R.X. Yuan, G.H. Chen, E. Blanco, J.M, Gao, X.T. Shuai, Polymer 49 (2008) 3477-3485 7 D.L. Shi, H.S. Cho, Y. Chen, H. Xu, H.C. Gu, J. Lian, W.Wang, G.K. Liu, C. Huth, L.M. Wang, R.C. Ewing, S. Budko, G.M. Pauletti, Z.Y. Dong, Adv. Mater. 21 (2009) 1-4.


91

PI-6: NITRILE CYCLIZATION REACTIONS OF POLYACRYLONITRILE FIBRES THERMO-OXIDATIVELY TREATED BY CONTINUOUS PROCESS

GEORGIOS MITSIS, SPYRIDON SOULIS, JOHANNIS SIMITZIS1 1Laboratory Unit “Advanced and Composite Materials”, Department III “Materials Science and

Engineering”, School of Chemical Engineering, National Technical University of Athens, 9 Heroon Polytechniou str., Zografou Campus, 157 73, Athens (Greece) – [email protected]

Abstract

Carbon fibres are commonly used as reinforcing material in composites. The demand for carbon fibres is growing rapidly year by year, as they are used in many applications such as aerospace, aeronautics, sports etc91,3. They are produced by carbonization of suitable precursor materials, the most important of them being polyacrilonitrile (PAN) fibres.3 The conversion from PAN solution to high-strength carbon fibres contains three key stages: spinning, stabilization and carbonization. The stabilization of precursor fibres is a very important process, depending on the proper course of many reactions, including oxidation, dehydrogenation and cyclization. The quality of oxidized fibres stongly influences the mechanical properties of the ultimate carbon fibres91. The stabilization treatment is usually performed at temperatures between 200 oC and 350 oC in air flow for about 30 min or more, following a heating program4. Modern stabilization method is to pass the precursor tow continuously through a oven divided into several zones with increasing temperature gradient to reduce the cost and improve the efficiency of entire process. During successive stabilization, temperature above 250 °C has more obvious influence on the oxidized fibres than that at initial stage2. The conversion of the main chemical reactions can be determined using various indexes based on Fourier-transform infrared analysis (FTIR)6. The aim of this work is the oxidative heat treatment of PAN homopolymer fibres by continuous process under isothermal conditions and the following of the main reactions, i.e. the cyclization of –CN (nitrile group) to >C=N- bond, by FTIR. The influence of the temperature and the residence time on these reactions is examined as well as the homogenity of the treated fibres at different lengths. Commercial PAN homopolymer fibres were isothermaly and continuously treated at temperatures between 220 °C and 285 °C in an oven equipped with a heating control device. The oven had seven heating zones each one having its own controller of temperature. Seven individual thermocouples were placed at the center of each zone to monitor the temperature. Air was supplied to provide the nessecary oxygen to maintain oxidative atmosphere during the process. The fibres were kept under tension, with a brake-type mechanism and were pulled through the oven. Oxidatively treated PAN fibres at the same conditions were cut at distances of 40 cm and the corresponding samples were prepared for FTIR analysis. The ratio of the intensity of the peak at 1250 cm-1 (wagging of C-H bond) to the intensity of the peak at 2240 cm-1 (nitrile group) is used as a measure of methine transformation. The normalized nitrile-to-methylene index, rnm , is calculated from the indensity of the nitrile peak (at 2240 cm-1) and the intensity of methylene peak (at 2940 cm-1). The conversion index, CI, takes into consideration also the intensity of conjugated double bonds peak (at 1600 cm-1)3. By increasing the temperature from 220 oC to 285 oC, the rnm index increases from 1,05 to 1,8 (as mean values) and the conversion index CI increases from 0,07 to 0,55 (as mean values). 1. Johannis Simitzis and Spyridon Soulis, “Correlation of chemical shrinkage of polyacrylonitrile fibres with

kinetics of cyclization”, Polym Int 57:99-105 (2008). 2. Min Jing, Cheng-guo Wang, Yu-Jun Bai, Bo Zhu, Yan-xiang Wang. “Effect of temperatures in the rearmost

stabilization zone on structure and properties of PAN-based oxidized fibers”, Polymer Bulletin 58, 541–551 (2007).

3. Spyridon Soulis and Johannis Simitzis, “Thermomechanical behavior of poly[acrylonitrile-co-(methyl acrylate)] fibres oxidatively treated at temperatures up to 180 oC”, Polym Int 54:1474-1483 (2005).

4. A. Shindo, “Polyacrylonitrile (PAN)-based Carbon Fibers”, Comprehensive Composite Materials, 2003, Chapter 1.01, Pages 1-33.

5. M.S.A. Rahaman, A.F. Ismail, A. Mustafa “A review of heat treatment on polyacrylonitrile fiber”, Polymer Degradation and Stability, Volume 92, Issue 8, August 2007, Pages 1421-1432.

6. Mameatea L. And Billingham N, Then E, Polym Degrad Stab 47:189-201 (1995).


92

PI-7: CARBONACEOUS ELECTRODES DERIVED FROM COMPOSITES OF NOVOLAC RESIN WITH OLIVE STONES BIOMASS FOR APPLICATION IN

ETHANOL OXIDATION OF FUEL CELLS ANASTASIA PIKASI, PANTELITSA GEORGIOU, JOHANNIS SIMITZIS



Abstract

Fuel cells have the potential to be highly efficient and environmentally clean sources of power. However there are complex technical issues to resolve1. Liquid fuels for fuel cells, such as low – molecular weight alcohols, have attracted the interest as they have advantages, compared to pure hydrogen because of their easy handling, storing and transportation as well as because of their energy densities which are comparable to that of gasoline. Ethanol is an attractive fuel for fuel cells2. Ethanol it is easy to be obtained, it is non – toxic and has a high specific energy3. The requirements for Proton Exchange Membrane Fuel Cells (PEM) materials are low – cost and high durability. Electrocatalysts play an important role to reduce the cost and improve the lifetime of fuel cells4. Supported catalysts are of special interest as they allow fine dispersion of metal particles. Carbons with high surface area and large pore volume have been used as catalysts support for many industrial catalysts5. Carbon – supported platinum (Pt) catalysts are the most commonly used electrocatalysts in PEM fuel cells6,7. The aim of this work is the manufacture of carbonaceous electrodes based on olive stones biomass in combination with novolac resin as binding agent and the investigation of these products for electrochemical applications, after electrodeposition of platinum on them. Composites were fabricated by mixing olive stones biomass (as grains with diameter less than 300 μm) in different proportions (80% and 60% w/w) and novolac (20% and 40%) with hexamethylenetetramine (“hexa”) as curing agent and the proper mixture was placed into small cylindrical moulds. The curing was performed by heating at 170 ºC for 30 min and the specimens were pyrolyzed under N2 atmosphere with a heating rate of 10 ºC/min up to 1000 ºC. The pyrolyzed specimens were first electrochemically treated in 0.1M H2SO4 aqueous solution in the potential range of -3V→+3V→-3V with scanning rate of 50mV/sec for 20 cycles in order to introduce oxygen – groups in their structure. Furthermore platinum was electodeposited on these specimens from a proper solution by cyclic voltammetry for different number of cycling (20 and 100 cycles), using the carbonaceous materials as working electrodes. The Pt- carbonaceous materials were examined for the electro-oxidation of ethanol. All electrochemical experiments were carried out in a conventional three-compartment glass cell at room temperature. The crystallographic planes of Pt – carbon of Pt deposited on carbon materials were characterized with X-Ray Diffraction (XRD). The morphology of carbon materials, used as electrodes, was characterized by SEM images and the presence of Pt was determined based on EDS analysis.

1 C.A.C. Sequeira, P.S.D. Brito, A.F. Mota, J.L. Carvalho, L.F.F.T.T.G. Rodrigues, D.M.F. Santos, D.B. Barrio,

D.M. Justo, Energy Conversion and Management 48, 2007, 2203-2220 2 C. Lamy, E. M. Belgir, J-M. Leger, Journal of Applied Electrochemistry 31, 2001, 799-809 3 Zhao – Hui Teng, Yu – Jiao Wang, Bing Wu, Ya – Wen Tang, Tian – Hong Lu, Ying Gao, Applied Catalysis

B: Environmental 84, 2008, 400-407 4 Sheng Zhang, Yuyan Shao, Xiaohong Li, Zimin Nie, Yong Wang, Journal of Power sources 195, 2010, 457-

460 5 Singaram Vengatesan, Hyoung – Juhn Kim, Soo – Kil Kim, In – Hwan Oh, Sang – Yeop Lee, EunAe Cho,

Heung Yong Ha, Tae – Hoon Lim, Electrochimica Acta 54, 2008, 856-861 6 Paul V. Shanahan, Lianbin Xu, Chengdu Liang, Mahesh Waje, Sheng Dai, Y.S. Yan, Journal of Power Sources

185, 2008, 423-427 7 Anastasia Pikasi, Pantelitsa Georgiou and Johannis Simitzis, Key Engineering Materials 446, 2010, 23-31


93

PI-8: MANUFACTURE AND CHARACTERIZATION OF COMPOSITE MATERIALS CONSISTED OF THERMOSETTING RESINS WITH

PYROMETALLURGICAL SLAG AS ADDITIVE ELENI VORRISI, LOUKAS ZOUMPOULAKIS, JOHANNIS SIMITZIS



Abstract

The utilization of industrial wastes is preferable compared to their disposal due to the saving of raw materials and the reduce of the cost on one hand and the reduce or even elimination of pollution on the other1. Pyrometallurgical slags as by-products of industrial processing constitute interesting waste solid products due to their enormous quantities and their chemical composition. Such by-products are very often disposed contributing negatively to the pollution1,2,3. The aim of this work is the investigation of an industrial slag as additive in the curing formulation of thermosetting resins. This industrial slag is a by-product of the recycling processing of lead acid batteries. Composite materials were fabricated with the use of three thermosetting matrices, i.e. novolac, epoxy resin and unsaturated polyester by applying casting and/or compression molding as formatting techniques. The weight loss of the slag heated at 110 oC was 2.4 % w/w and remained constant after 30 min. The slag was heated at 750 oC for two hours and the weight loss was ~4.5 % w/w. The slag was heated at 110 or at 750 oC for residence time 2 h for both cases. They were used as additives in different percentages between 5 up to 50 % w/w in relation to the ultimate composite. For comparison reasons composites with typical additives, such as CaO and CaCO3 were also manufactured. The two forms of the slag additives were qualitatively and quantatively analyzed with X-Ray Fluorescence Spectrometry (XRF) and SEM/EDAX, determining as main constituents Fe (above 40 % w/w), Pb (5-8 % w/w) and S (3 % w/w) in the form of oxides or sulfate salts. The surface morphology of the composite materials was determined with Scanning Electron Microscope (SEM). The mechanical properties of the composite materials were measured, as well as their electrical conductivity with the DC method. Representative results are presented in Table 1. Table 1. Mechanical and electrical properties of composites based on epoxy resins.

The composite materials of epoxy resin with slag content of 10% have similar mechanical properties with commercial ones which are used as putty and contain the same content of additive (CaO or CaCO3). Composite materials with CaO as additive have the same magnitude order (10-14) for their electrical conductivity with the composites of slag-epoxy.

1 Caijun Shi, Jueshi Qian, Resources, Conservation & Recycling, 29 (2000), 195-207 2Yunjiao Li, Ilya Perederiy, Vladimiros G. Papangelakis, J. Haz. Mat., 152 (2008), 607-615 3 Dirk Durinck, Fredrik Engstrom, Sander Arnout, Jeroen Heulens, Peter Tom Jones, Bo Bjorkman, Bart Blanpain, PatrickWollants, Resources, Conservation & Recycling , 52 (2008), 1121-1131

Resin Formatting Technique

Additive (10 % w/w) Shear strength τb

(MPa)

Electrical Conductivity σ

(S/cm) Slag 110 oC Slag 750 oC CaO / CaCO3

Epoxy resin

casting

x - - 13,19 4,57 x 10-14 - X - 13,11 2,16 x 10-14 - - CaO 13,19 7,84 x 10-14 - - CaCO3 13,18 1,06 x 10-11

compression molding

x - - 6,68 3,47 x 10-13 - X - 7,14 3,68 x 10-13


94

PI-9: ELECTROPOLYMERIZATION OF THIOPHENE ΟNTO MODIFIED CARBON FIBRES ELECTRODES

DESPINA TRIANTOU, PANTELITSA GEORGIOU, SPYRIDON SOULIS, JOHANNIS SIMITZIS

National Technical University of Athens, School of Chemical Engineering, Department III “Materials Science and Engineering“, Laboratory Unit “Advanced and Composite Materials", 9 Heroon Polytechniou str., Zografou Campus, 157 73 Athens, Greece, e-mail : [email protected]

Abstract

The electrochemical deposition of conducting polymers (CPs) onto carbon substrates, e.g. carbon fibres, has been studied with the goal of improving the properties of these polymers, so as to use them as electrodes in different applications, e.g. batteries and biosensors1,2. Polythiophene and its derivatives are important class of CPs since they are stable in air and moisture both in doped and undoped states3. The aim of this work is the electropolymerization of thiophene (Th) onto modified carbon fibres, which could be used as novel electrodes. Commercial carbon fibres (CF) were pyrolyzed up to 1000 oC under nitrogen atmosphere with a residence time of 30 min at this temperature (symbolized as PCF). The latter were electrochemically pretreated by cyclic voltammetry4 (Table 1). The carbon fibres were used as working electrode for electropolymerization of Th (0.1 M) by cyclic voltammetry in the potential range from 0 up to +2 V (40 sweeps, scan rate: 100 mV/s). Acetonitrile was used as a solvent and tetrabutylammonium tetrafluoroborate (0.1 M) as supporting electrolyte. In Table 1 the characteristics of the polymer coated onto the electrodes are also presented. Table 1. Electropolymerization of thiophene (Th) οnto different working electrodes and characteristics of

polymer coated οnto the electrode

Cod

e Working electrode Polymer coated οnto the electrodes

Platinum Carbon fiber Electrochemical pretreatment (modified carbon fibers in 5% w/w H2SO4)

Thickness (μm)

Electrical condu-ctivity (S/cm)

Energy gap (eV)

CF - Pristine (CF) - - 7.0 x10-2 - PTh + - - 2.00 7.5 x10-3 * 1.63 PTh1 - Pristine (CF) - 2.13 4.0 x10-2 1.45 PTh2 - Pyrolyzed (PCF) - 1.39 4.7 x10-1 1.40 PTh3 - Pyrolyzed -1 V→ +1.5 V→ -1 V, (PCF-N) 1.93 7.0 x10-1 0.80 PTh4 - Pyrolyzed -3 V→ +3 V→ -3 V, (PCF-W) 1.73 6.4 x10-2 1.30

* This conductivity is that of free-standing polythiophene film

During the electropolymerization of Th onto CF, a broad oxidation peak (ranging from 1 V up to 1.6 V) and a broad reduction peak (from 0.6 V up to 0.85 V) appear and the current of the peaks continuously increases. The oxidation peak (due to the doping of the polymer5) shifts to higher potential with increasing sweeps, whereas the reduction peak (due to the undoping) shifts to lower potential. This behavior is the same as in the case of the polymerization of Th οnto platinum. A totally different behavior is observed when pyrolyzed and pretreated pyrolyzed fibres were used. Specifically, the oxidation of Th starts at 0.5 V and the corresponding current increase abruptly, whereas the reduction starts at 1.4 V. This decrease of the oxidation potential is advantageous for better and easier electron transfer6. In the FTIR spectra, all polymers exhibit the characteristic bands of polythiophenes (PTh), i.e. at 1650-1600 cm-1 and at 1500 cm-1 due to aromatic ring vibrations and at 1080-1036 cm-1 due to C-H vibrations2,4. Based on SEM, the most uniform PTh films were formed onto pyrolyzed carbon fibres. The carbon fibres PTh/PCF-N exhibit higher electrical conductivity than the PTh film (coated οnto platinum). The different behavior of modified carbon fibres is attributed to their electrochemical pretreatment. PCF-W carbon fibres contain many groups, as electron acceptor (e.g. C=O) and donor groups (e.g. C-OH) in opposite to PTh/PCF-N carbon fibres which contain few groups, mainly as quinone- and hydroquinone- type groups4. In conclusion, uniform PTh films were formed onto electrochemical pre-treated carbon fibres, leading to new, low cost electrodes with perspectives to be used as novel electrodes in many applications.

1 C. Dalmolin, S.C. Canobre, S.R. Biaggio, R.Rocha-Filho, N. Bocchi, J. Electroanal. Chem., 578 (2005), 9-15 2 M. Ates, A. Sarac, Progr. Org. Coat., 66 (2009), 337-358 3 J. Simitzis, D. Triantou, S. Soulis, J. Appl. Polym. Sci., 118 (2010), 1494-1506 4 P. Georgiou, J. Walton, J. Simitzis, Electrochim. Acta, 55 (2010), 1207–1216 5 B. Sari, M. Talu, F. Yildirim, E.K. Balci, Appl. Surf. Sci., 9493 (2002), 1-12 6 A. Sarac, H. Geyik, E.A. Parlak, M. Serantoni, Progr. Org. Coat., 59 (2007), 28-36


95

PI-10: AMPHIPHILIC BLOCK COPOLYMER SELF-ASSEMBLED

NANOTEMPLATES FOR SIZE- AND SHAPE-CONTROLLED GROWTH OF INORGANIC NANOSTRUCTURES

ANNA PERDIKAKI1,2, ELENI VERMISOGLOU1, GEORGIOS N. KARANIKOLOS1, NIKOLAOS BOUKOS2,

JOHANNIS SIMITZIS3, NIKOLAOS KANELLOPOULOS1

Institutes of 1Physical Chemistry and 2Materials Science, Demokritos National Research Center, 15310 Athens (Greece)- [email protected]

3School of Chemical Engineering National Technical University of Athens, 157 80 Athens (Greece)

Abstract Synthesis of nanostructures is an emerging field in solid state chemistry. Due to their small sizes and large specific surface areas, these crystallites exhibit exciting properties that differ significantly from those of the bulk materials1. We present the synthesis of metallic and semiconductor (ZnO) nanoparticles in templates formed by self-assembly of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) amphiphilic block copolymers in selective solvents. Controlled synthesis of zero-, one-, and two-dimensional nanostructures by using cubic, hexagonal and lamellar lyotropic liquid crystals as templates takes place, respectively. The liquid crystals were formed by self assembly in a ternary system in inert atmosphere consisting of the block copolymer, heptane as the non-polar dispersed phase, and formamide as the polar continuous phase2. The morphology and size of the obtained particles was determined by Transmission Electron Microscopy and by observing changes in the Photoluminescence (PL) emission, X-Ray Diffraction and UV-Visible spectra.

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1“Synthesis and Size Control of Luminescent ZnSe Nanocrystals by a Microemulsion-Gas Contacting Technique”, G.N. Karanikolos, et. al. Langmuir 20, 550(2004). 2“Templated Synthesis of ZnSe Nanostructures Using Lyotropic Liquid Crystals”, G.N. Karanikolos, et. al. Nanotechnology 16, 2372-2380 (2005)

Figure 1. TEM image of Ag nanoparticles Figure 2. UV-vis spectrum of Ag nanoparticles.


96

PI-11: STUDY OF THE EFFECT OF MAGNETIC FIELD ON GAS SEPARATION

PERFORMANCE OF MAGNETIC NANOCOMPOSITE POLYMERIC AND CARBON HOLLOW FIBER MEMBRANES

NIKOS HELIOPOULOS1, EVANGELOS FAVVAS1, SERGIOS PAPAGEORGIOU1, DIMITRIOS PETRIDIS2 AND NICK KANELLOPOULOS1

1Institute of Physical Chemistry, N.C.S.R. “Demokritos”, 15310, Aghia Paraskevi, Attica, Greece) – [email protected]

2Institute of Materials Science, N.C.S.R. “Demokritos”, 15310, Aghia Paraskevi, Attica, Greece

Abstract

In this work, nanocomposite γ-Fe2O31

/ PI polymeric hollow fiber membrane as well as their derivative carbon nanocomposite hollow fiber membranes were prepared and characterized using advanced techniques such as SEM, TEM, XRD, SQUID, gas permeability etc. Characteristic results of the abovementioned techniques can be seen in Figure 1.

0

500

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nsity

XRD spectrum of γ-Fe2O3 nanoparticles

TEM image of γ-Fe2O3 nanoparticles

SEM image of polymeric nanocomposities HFM1 (Cross section)

SEM image of nano-composities carbon HFM (Cross section)

Fig. 1. XRD spectrum, TEM image for γ-Fe2O3 magnetic nanoparticles and SEM images of γ-Fe2O3/PI polymeric hollow fiber membrane and derivative carbon hollow fiber membrane. 1HFM: Hollow Fiber Membrane.

Nanocomposite polymeric γ-Fe2O3/PI hollow fibers were initially prepared by the dry/wet phase inversion process in a spinning set-up, as described previously2. The derivative carbon nanocomposite membranes were produced by pyrolysis of the polymeric precursors up to 900 οC under Ar flow. He, H2, O2, N2, CO2 and CH4 permeability experiments conducted on precursor and carbon membranes, with and without nanoparticles in and out of magnetic field, revealed a decrease in permeability but a significant increase in selectivity coefficients of the carbon membranes compared to their polymeric precursors. Interesting results were obtained for the O2/Ν2 gas pair due to the differences in their magnetic properties. Specifically in the presence of magnetic γ-Fe2O3 nanoparticles the selectivity of the carbon membranes for the Ο2/Ν2 gas pair was 71.8% higher than the precursor while under the influence of a magnetic field a 1047.4% increase was measured! However, the application of a magnetic field in the presence of magnetic nanoparticles resulted in a 16.7% reduction of the selectivity coefficient for the Ο2/Ν2 pair. 1 A. B. Bourlinos, et al. J Mater Sci. 41, 2006, 5250 – 5256. 2 E. P. Favvas, et al. J of Porous Materials 15 (6), 2008, 625 – 633.

Gases

Ideal Selectivity

γ-Fe2O3/PI HFM Carbon HFM

Carbon HFM + magnetic

field

Carbon / γ-Fe2O3

Carbon / γ-Fe2O3 + magnetic

field H2/CH4 3.89 1466.9 7169.9 983.9 2037.9 O2/N2 0.97 7.8 89.5 13.4 6.5

CO2/CH4 0.74 13.3 79.0 8.1 20.2 N2/CH4 0.76 1.0 0.7 0.7 2.2 CO2/Ν2 0.97 12.7 117.1 11.8 9.0 H2/CΟ2 5.25 110.1 90.8 121.1 101.1

Table 1. Ideal selectivity coefficients for 5 studied membranes (polymeric and carbon HFM).


97

PI-12: INVESTIGATION OF STRUCTURAL PROPERTIES OF PVA/BENTONITE NANOCOMPOSITES USING NEUTRON DIFFRACTION

ANDREAS SAPALIDIS, FOTIOS KATSAROS, THEODORE STERIOTIS AND NICK KANELLOPOULOS

Insitute of Physical Chemistry, National Center of Scientific Research “Demokritos” Terma Patriarxou Grigoriou kai Neapoleos, Aghia Paraskevi, Athens, Greece

Abstract

The aim of these series of experiments is to study polymer nanocomposites using neutron membrane diffraction and to investigate thoroughly the structural changes (crystallinity, swelling, disordering and migration of clay layers) as a function of the relative humidity of the composites. V1 diffractometer (BENSC) was extremely well suited in this respect, not only due to its geometry but also because of the unique sample environment (in terms of controlled relative humidity) and pertinent know-how available.

Polyvinyl alcohol (Mowiol 5-88) – Bentonite nanocomposites films with clay loading of 5,10 and 20% by weight with thickness of approximately 100μm were cut in 6 x 1cm rectangular shape and placed between quartz plates for the measurements. The diffraction patterns obtained from lamellar and in-plane sample positions revealed that there is a specific orientation of bentonite plates, parallel to the film surface. This conclusion is in agreement with the results obtained from XRD measurements and gas permeability technique, in which the well organized and dispersed impermeable inorganic layers, increase the resistance in flow throw the nanocomposites film, acting as gas barriers. In addition, measurements on hydrated samples enabled us to enlighten specific regions of the diffraction spectra. More specific, hydrated with H2O samples, were measured in order to monitor the structural changes as a function of the relative humidity of the composites at low Q region (inorganic rich region). On the other hand, diffraction experiments on pre-equilibrated with D2O samples revealed the structural changes in polymeric matrix, due to hydration. The obtained peak at 0.66-0.72 Å-1 can be attributed to the presence of a new crystalline phase, presumably induced by the presence of the silicates. Finally, measurements on pure PVA samples revealed a gradual dissolution of the polymer crystallites above 55% RH. At 95% RH the crystalline phase is almost disappeared. On contrary, in the case of nanocomposites, the crystallinity remains unaffected of hydration up to 95%.

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D2O

a) b) Figure: Neutron diffraction patterns of a) PVAB20 and PVA and b) PVAB20 equilibrated in H2O and D2O


98

PI-13: POLYMERIZATION KINETICS OF POLY(STYRENE-CO-METHYL

METHACRYLATE) BASED NANOCOMPOSTES PREPARED BY IN SITU BULK POLYMERIZATION

VASILIKI MPOZANI, ALEXANDROS K. NIKOLAIDIS, DIMITRIS S. ACHILIAS

Laboratory of Organic Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece – [email protected]

Abstract

Polymers reinforced with a small amount of montmorillonite (MMT) clay have attracted a great deal of research interest in the past decade. These nanocomposites exhibit improved mechanical properties, higher thermal stability and better barrier properties1. Different preparation methods for the polymer/MMT nanocomposites have been studied, including solution, or melt intercalation and in situ polymerization. Among them, dispersing in situ polymerization may be the most desirable method for preparing nanocomposites, because the types of nanoparticles and the nature of polymer precursors can vary in a wide range to meet the requirements. From the structural point of view, two idealized polymer-clay nanocomposites are possible: intercalated and exfoliated. Intercalation results from the penetration of polymer chains into the clay’s interlayer region, usually, preserving the ordered layer structure. By contrast, exfoliation involves extensive polymer penetration and silicate crystallites delamination and the individual nanometer-thick silicate platelets are randomly dispersed in the polymer matrix. Moreover, since clay is naturally hydrophilic and inherently incompatible with most organic polymers, several methods have been studied, including surface ion exchange, to make clay compatible with polymer. Since the polymerization of MMA and styrene have been widely investigated in literature2, in this research, synthesis of nanocomposites based on poly(styrene-co-methyl methacrylate) copolymer matrix was investigated with different types and amounts of, commercially available, organomodified MMT clays under the trade name Cloisite. The in situ bulk polymerization technique was followed. The main objective was to investigate if free radical polymerization kinetics is affected by the presence of montmorillonite nanoparticles. Reaction kinetics was measured using Differential Scanning Calorimetry (DSC) by recording the amount of heat released versus time under isothermal conditions and eventually calculating the time evolution of polymerization rate and monomer conversion. The gravimetric technique to monitor monomer conversion during polymerization at pre-specified time intervals was also examined and the results were compared. The structure and morphological characteristics of the nano-hybrids produced was verified by means of X-Ray diffraction (WAXD), scanning electron microscopy (SEM) and FTIR spectroscopy. Their glass transition temperature was measured with DSC and a dynamic mechanic analyzer (DMA). The average molecular weights and the full molecular weight distribution of the materials formed was measured with Gel Permeation Chromatography (GPC). Their thermal stability and degradation kinetics was investigated using Thermogravimetric analysis (TGA). Finally, the mechanical properties of the nanocomposites were investigated using DMA and a dynamometer.

The WAXD measurements revealed the appearance of either exfoliated or intercalated structures. From the kinetic experiments it was observed that the presence of OMMT nanoparticles slightly enhances the polymerization rate and shortens the polymerization time to achieve a specific monomer conversion, depending on monomer type. The Tg of the nanocomposites was found to be higher than the corresponding of neat copolymers. Finally, from the TGA measurements it was clear that the nanocomposites exhibited higher thermal stability compared to neat P(S-co-MMA) copolymers. An increase in the amount of nanofiller increased the thermal stability of the hybrid materials.

1 Mai, Y.-W., Yu Z.-Z., Polymer Nanocomposites. Cambridge, Woodhead Publishing Ltd, 2006 2 Nikolaidis, A.K., Achilias, D.S., Karayannidis, G.P., Ind. Eng. Chem. Res., 2010, in press.


99

PI-14: EFFECT OF THE ORGANO-MODIFIED NANO-REINFORCEMENT ON THE THERMAL PROPERTIES OF POLY(3-HYDROXYBUTYRATE)-BASED

HYBRID MATERIALS ELPINIKI PANAYOTIDOU1,2, DIMITRIS S. ACHILIAS1, IOANNIS ZUBURTIKUDIS2

1 Department of Chemistry, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece, E-mail: [email protected]

2 Department of Industrial Design Engineering, TEI of Western Macedonia, Kozani 50100, Greece

Abstract

Poly(3-hydroxybutyrate) (PHB) is a fully biodegradable, thermoplastic aliphatic polyester, produced by a wide variety of bacteria from cheap renewable raw materials, which has some physical and mechanical properties comparable to those of isotactic polypropylene. Because of these properties, PHB has attracted much industrial attention. However, it has some drawbacks such as stiffness, brittleness, and most of all very low thermal stability at processing temperatures slightly higher than its melting point that prevent its larger commercial applications. The thermal instability of PHB in the melt prevents it from substituting the non-biodegradable polymeric materials in commercial products. That is why improving the thermal stability of PHB is very important. There are several approaches to overcome these drawbacks of PHB: (a) biosynthesize series of copolymers containing hydroxyalcanoate units other than 3-hydroxybutyrate units, (b) prepare miscible blends of PHB with another biodegradable polymer with suitable properties or plasticizer, and (c) synthesize block copolymers based on PHB. As an alternative to these conventional methods, the preparation of PHB nanocomposites is investigated here. Various loadings of montmorillonite organically modified by octadecylamine (C18MMT) were dispersed in PHB using a micro-extruder/compounder. The aim was to produce hybrid material with improved thermal properties over the pristine PHB. Constant nitrogen flow during nanocomposite preparation prevented thermal decomposition of the matrix. The nanocomposites were characterized by differential scanning calorimetry (DSC), polarized optical microscopy (POM), X-ray diffraction (XRD) (Figure 1) and scanning electron microscopy (SEM). Then, the non-isothermal degradation of pure PHB and PHB/OMMT nanocomposites, as well as the influence of C18MMT on the thermal stability of PHB, was investigated and a detailed kinetic analysis of the process was performed using model-based and model-free methods. Indicative results appear in Figure 2.

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Figure 1. X-ray diffraction patterns of neat PHB and nanocomposites

Figure 2. Thermal degradation curves of PHB (a) and PHB nanocomposites with 1 wt% (b), 3 wt% (c), 5 wt% (d) and 10 wt% C18MMT (e).

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100

PI-15: STUDY OF COALESCENCE DURING PVDF/PMMA BLEND PREPARATION

SEDIGHEH FARZANEH, MONIR ASGARPOUR, ABBAS TCHARKHTCHI

Arts et Métiers ParisTech 151 bd de l’Hôpital 75013 Paris-France

Abstract

Poly(vinylidene fluoride) (PVDF)/poly(methylmethacrylate) (PMMA) blend has been employed in different field of polymer industry. The preparation of this blend is basically affected by coalescence phenomenon of the grains. In this study we have tried to analyze this effect and to see the role of different physical parameters like viscosity, relaxation time, surface tension, diffusion, solubility and so on. The grains of these two polymers were been heated under optical microscope in order to follow the coalescence. The coalescence of the particles in contact begins by formation of an interface between them. There are different steps during coalescence as it is shown in figure 1.

Figure 1: Different steps of coalescence

In order to characterize the initial polymers and to study the characteristics of blend, different analytical methods have been used like infrared spectrometry, differential scanning calorimetric, dynamic-mechancal-thermal analysis, tensile test machine,… A mathematical model has been proposed to follow the increase of the interface between PMMA and PVDF grains during their coalescence. Key words: PMMA, PVD, blend, coalescence, References: 1 – M. A. Aao, J. L. Throne, “Principles of rotational molding”, Polymer Engineering and Science, 12, n°4: 237-264, 1972 2 – S.Mazur, “Coalescence of polymer particles”, Polymer powder technology”, page 157, 1995 3 – U. Sundararaj, C. W. Macosko,”Drop breakup and coalescence in polymer blends: the effects of concentration and compatibilization”, Macromolecules, 28:2647, 1995 4 – M. Narkis, “Sintering behavior of polymethyl methacrylate particles”, Polymer Engineering and Science, 19: 889-892, 1979


101

PI-16: WATER UPTAKE CHARACTERISTICS INTO THE TS-1 ZEOLITE EFFECT ON PHYSICAL PROPERTIES AND BIODEGRADABILITY FOR

POLY(BUTYLENE SUCCINATE) (PBS)-TITANIUM SILICATE (TS-1) ZEOLITE HYBRID MATERIALS

SUNG-YEON HWANG1, EUI –SANG YOO2, SEUNG-SOON IM1* 1Department of Fiber and Polymer engineering, College of Engineering, Hanyang University, 17

haengdang-dong, seongdong-Gu, Seoul (Republic of Korea) – [email protected] 2KITECH textile Ecology Laboratory, 1271-18 Sa 1 Dong, Sangrokgu, Ansan City, Gyungido,

(Republic of korea)

Abstract

The objective of this study was to investigate how can affect the wateruptake feature int TS-1 zeolite on physical, rheological properties, morphological parameters, and enzymatic hydrolysis for PBS/TS-1 zeolite hybrid composite. TS-1 zeolite can act as reinforcement filler, resulted that PBS/TS-1 zeolite hybrid composite showed remarkable increase in physical properties. The rheological properties of PBS/TS-1 zeolite hybrid composite with high zeolite contents showed low values of complex viscosity compared with PBS/TS-1 zeolite hybrid composite with low zeolite contents due to volatilization of water released from the zeolite pores. The introduction of TS-1 zeolite in PBS matrix is not significantly affected the change of the size of long period, lamella thickness and amorphous region, indicating PBS chains cannot penetrate into zeolite pores, as was revealed by the SAXS profiles. In case of enzymatic hydrolysis for several weeks, the enzymatic hydrolysis rates of PBS/TS-1 zeolite hybrid composite were significantly accelerated with increasing TS-1 zeolite contents compared with Homo PBS. This result indicated that TS-1 zeolite can act as the role of carrier for enzyme activation, resulting enzymatic hydrolysis occur from amorphous area of surface into inside film.

Figure 1. FT-IR spectra of volatilized water in (a) Homo PBS,(b) TS20,and (c) the rate of weight loss for TS20 during the phase transition from 20°C - 150°C.


102

PI-17: THE INFLUENCE OF TACTICITY ON STATICS AND DYNAMICS OF POLYMER MELTS: RESULTS FROM ATOMISTIC AND COARSE-GRAINED

SIMULATIONS DOMINIK FRITZ1, VAGELIS HARMANDARIS2, NICO VAN DER VEGT1, KURT KREMER1

1Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany – [email protected]

2Department of Applied Mathematics, University of Crete, 71110 Heraklion, Greece

Abstract

We perform molecular dynamics computer simulations of polymer melts. Since it is computationally not feasible to equilibrate systems of long polymer chains in full atomistic detail, we developed a coarse-grained model for polystyrene, which merges groups of atoms into “superatoms”1,2. These “superatoms” interact via coarse-grained effective interaction potentials. The overall speed-up in comparison to fully atomistic molecular dynamics simulations is more than 4 orders of magnitude. The coarse-grained model preserves the information about the tacticity of the polystyrene chains and reproduces the local chain conformations as well as the chain stiffness. Statical properties of coarse-grained melts of different tacticities agree with statical properties of fully atomistic melts as well as with experimental results. Furthermore, the coarse-grained model allows to study dynamical properties of polystyrene melts, where the different tacticities lead to differences in the entanglement molecular weights, and the dynamics of small additives in a matrix of long chains3.

1 Harmandaris, V. A.;Adhikari, N. P.; van der Vegt, N. F. A.; Kremer, K., Macromolecules, 2006, 39, 6708. 2 Fritz, D.; Harmandaris, V. A.; Kremer, K.; van der Vegt, N. F. A., Macromolecules, 2009, 42, 7579. 3 Fritz, D.; Herbers, C. R.; Kremer, K.; van der Vegt, N. F. A., Soft Matter, 2009, 5, 4556.


103

PI-18: POLYMERS UNDER EQUILIBRIUM AND NON-EQUILIBRIUM CONDITIONS: FROM ATOMISTIC TO COARSE-GRAINED MODELS

V. HARMANDARIS1,2, K. KREMER2, C. BAIG3 1University of Crete, Department of Applied Mathematics, Heraklion, GR-71409 Crete, FORTH-

IACM (Greece) – [email protected] 2Max-Planck-Institute for Polymer Research, D-55021 Mainz, (Germany)

3University of Patras, Department of Chemical Engineering, Patras, FORTH-ICE/HT, (Greece)

Abstract

Molecular simulations are a very useful tool for the study of polymeric material. Because of the very broad range of length and time scales characterizing macromolecules, multi-scale simulation methodologies that involve information from various levels of description needed.1 Here we present results concerning polymers, under equilibrium and non-equilibrium conditions, through such a hierarchical multi-scale simulation approach. The proposed methodology consists of two stages.2-3 The first one involves state-of-the-art atomistic molecular dynamics (MD) simulations of small systems. In the second stage a CG model for the polymer chain is developed using static and dynamic information from the atomistic simulations. With this systematic approach structure and dynamics of polymer can be quantitatively predicted through the CG simulations and directly compared to experimental.3 As a test case polystyrene (PS) melts are examined. Results about bulk PS melts at equilibrium are predicted for a very broad range of length and time scales (more than 10 orders of magnitude) and also compared very well with experimental data for molecular weights up to 50.000gr/mol.3

Furthermore, non-equilibrium polymeric liquids (PS) under shear flow are examined by performing atomistic and CG non-equilibrium MD (NEMD) simulations.4 By studying both structural (chain conformation and pair distribution function) and dynamical (relaxation time and diffusion coefficient) properties as a function of the shear rate, we found that the large-scale chain conformation is reasonably well predicted by the CG model up to an intermediate flow strength (Weissenberg number Wi<10), beyond which, however, a significant discrepancy between the atomistic and the CG models is developed; this is attributed to excessively large chain deformations allowed in the CG model (compared to the atomistic model) due to relatively weak energies for local bonded interactions between CG beads.

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ol)

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Figure 1: (a) Self-diffusion coefficient of PS melts from CG MD simulations and experiments, (b) Conformation tensor as a function of Wi from CG and atomistic NEMD simulations.

1 “Simulation Methods for Polymers” edited by Theodorou, D. N., Kotelyanski, M., (Marcel Dekker: New York, 2004). 2 V. Harmandaris et al. Macromolecules 36, 1376 (2003); Macromolecules 39, 6708 (2006); Macrom. Chem. and Physics, 208, 2109 (2007). 3 V. Harmandaris and K. Kremer Macromolecules 42, 791 (2009); Soft Matter 5, 3920 (2009). 4 C. Baig and V. Harmandaris Macromolecules 43, 3156 (2010).


104

PI-19: PROPAGATION RATE CONSTANTS OF SOME MONOMERS IN AQUEOUS SOLUTION STUDIED BY PULSED RADIATION POLYMERIZATION IN

CONJUCTION WITH SIZE-EXCLUSION CHROMATOGRAPHY NINA BARTOSZEK, SŁAWOMIR KADŁUBOWSKI, PIOTR ULAŃSKI, JANUSZ M. ROSIAK

Institute of Applied Radiation Chemistry, The Faculty of Chemistry, Technical University of Lodz, Wróblewskiego 15, 90-924 Łódź (Poland) – [email protected]

Abstract

Since synthetic polymers started playing a significant role in our modern life, the need for inventing new functional polymers has appeared. To achieve that, new methods of synthesizing polymers with controlled structure and properties have been developed and are constantly being improved. This requires precise knowledge about the kinetics and mechanism of polymerization and crosslinking reactions. In the last 20 years, new methods for determination of rate coefficient of individual elementary reactions in the polymerization processes have been proposed and tested. Despite the significant development of these methods, they still have some drawback (simplification assuming the independence of the rate constants of chain length and concentration or the type of initiator) and the interpretation of obtained results may be somewhat ambiguous. The situation has dramatically improved since pulsed laser polymerization (PLP) with molecular weight analysis by size exclusion chromatography (SEC) was invented. The use of PLP-SEC method has been recommended by IUPAC and nowadays this technique has become the standard tool for obtaining propagation rate coefficients for homo- and copolymerizations.

The basic idea of pulsed laser polymerization is simple. The mixture containing monomer and photoinitiator is irradiated by a series of laser pulses. This leads to generation of radicals which initiate polymerization. A significant number of polymer chains which are initiated during one pulse are terminated with a radical produced during the subsequent one. Other chains are terminated by the second, third, etc., pulse and well-structured molecular weight distribution (MWD) is formed. Analysis of the MWD enables determination of the propagation rate coefficient, kp.

Our study concerns developing a procedure similar to PLP-SEC, but based on different initiation mechanism. We would like to follow an idea proposed several years ago by van Herk et al., and replace pulses of light with pulses of ionizing radiation, which lead to formation of monomer radicals with no initiator present in the system.. Our goal was to test this new method to determine the rate constants of propagation, based on exposing monomer solution to a series of fast electrons pulses and chromatographic analysis of products. We expect that this method will allow to conduct research in pure monomer or monomer-solvent system without additives as well as in heterogeneous, non-transparent systems.

Our first pulsed radiation polymerizations were carried out using N-vinylpyrrolidone (NVP) as a monomer. We used linear accelerator ELU-6E to generate pulses of fast electrons - duration time of 3 ns. The pulse repetition rate was 50 Hz. The polymerizations were carried out at different monomer concentrations and number of pulses. Molecular weight distributions (MWDs) were determined by HPLC-GPC using water as the eluent at 30 °C and a flow rate of 0,5 ml/min. Data acquisition and processing were carried out using the WinGPC software.

We obtained well-structured MWDs, with clear points of inflection. The ratio of molecular weights for the first and second peak are close to 0,5, in accordance with criteria defined by IUPAC for PLP-SEC. What is also important, the obtained values are in good agreement with the propagation rate coefficients obtained for NVP in water by PLP-SEC method. Our results indicate that pulsed radiation polymerization in conjunction with aqueous-phase SEC can be successfully applied to study propagation rate constants of the NVP monomer. Tests on other water-soluble monomers are currently in progress.

Acknowledgements: The work was financed in part by Ministry of Science and Higher Education, Poland (503/6.PR UE/2007/7) and European Commission (project “ARTEMIS” under 6 Framework Programme).


105

PI-20: TAILORING THE POROUS STRUCTURE OF POLY(D,L LACTIC ACID)/CLAY NANOCOMPOSITES

ATHANASIA TSIMPLIARAKI1, IOANNIS TSIVINTZELIS1, SOTIRIOS MARRAS2, IOANNIS ZUBURTIKUDIS2, COSTAS PANAYIOTOY1

1Department of Chemical Engineering, Aristotle University of Thessaloniki, 54124 (Greece) – [email protected]

2Department of Industrial Engineering, TEI of Western Macedonia, Kozani 50100 (Greece)

Abstract Poly(DL-lactic acid)/clay nanocomposites (NC) were prepared using either the solvent casting or the extrusion method and their films were then processed with supercritical CO2 using the batch foaming technique (pressure quench). The effect of clay loading, the surfactant type and its organic cation concentration (CEC) during clay modification on the final porous structure was investigated through a series of experiments where all other parameters were kept constant as summarized in Table 1.

Table 1. Experimental conditions for the supercritical treatment of the three series of nanocomposites.

Parameters 1st series of NC clay loading varying

2nd series of NC surfactant type varying

3rd series of NC % CEC varying

Clay content, wt% 0, 1, 3, 5, 9, 15 3 3

Surfactant (CH3(CH2)n-1NH3Cl) n=4, 8, 12, 16, 18 n=16

% CEC 95 150 50, 75, 100, 150, 200

NC preparation method Extrusion Solvent Casting Solvent Casting

Foaming conditions 45 oC, 120 bar 45 oC, 150 bar 45 oC, 150 bar 45 oC, 150 bar

The morphology of the produced nanocomposites was investigated using X-ray analysis and their

porous structures were explored by scanning electron microscopy (SEM). Image processing of the samples revealed that the final cellular structure (pore diameter, cell density and bulk foam density) strongly depends on the clay loading and on the type and the organic cation concentration of the alkylammonium used for the modification of the clay. The results suggest that the size of pores decreases with the increase of clay loading, or the surfactant’s carbon chain or the cation concentration in clay, while there is a leveling off in pore size in all three cases.

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Figure 1. Effect of clay content on the average pore diameter (a), on the cell density (b), and on the bulk foam density (c) for two different sorption pressures of CO2.


106

PI-21: THERMODYNAMIC CHARACTERIZATION OF FLUORINATED METHACRYLIC POLYMERS

STELLA.K. PAPADOPOULOU1 , COSTAS. PANAYIOTOU1

1 Department of Chemical Engineering, Aristotle University of Thessaloniki, 54124, Thessaloniki, Greece – [email protected]

Abstract

Fluorinated methacrylic polymers demonstrate unique properties, such as low surface energy, good wettability, adhesion and solvent resistance. These characteristics stem from the presence of highly stable C-F bonds. These polymers are thus extensively applied as high-performance coatings to obtain water repellent, antifouling, low-friction, and non-sticky surfaces. Their main drawback is their insolubility in most of the solvents commonly used for coating applications1. The goal of this study is to investigate the thermodynamic properties of the fluorinated polymers Poly(2,2,3,3,3 pentafluoropropyl methacrylate) (PPFPMA) and poly(1,1,1,3,3,3 hexafluoroisopropyl methacrylate) (PHFIMA) by means of Inverse Gas Chromatography (IGC). PPFPMA and PHFIMA were synthesized by free radical polymerization reactions. IGC is a powerful tool for the characterization of different types of materials, providing a wealth of information considering the surface and thermodynamic properties of the material under study2. The specific retention volume of 15 solvents, used as probes, was used for the assessment of the Flory–Huggins interaction parameter, the weight fraction activity coefficient, the molar heat, energy and entropy of sorption, the partial heat of mixing of the probes, as well as the solubility parameter of each polymer. The results of this work demonstrate that the polymers are insoluble in a wide range of solvents, even at elevated temperatures3. Moreover, the values of the Flory–Huggins interaction parameters and the weight fraction activity coefficients of the probes indicate that the more fluorinated polymer is more insoluble. The total solubility parameter of each polymer decreases slightly with the increase of temperature, while the solubility parameter of the more fluorinated polymer (PHFIMA) is lower than the corresponding value of PPFPMA.

1 Signori F., Lazzari M., Castelvetro V., Chiantore Ο., Macromolecules 39, 1749 (2006). 2 Voelkel A., Strzemiecka B., Adamska K., Milczewska K. Journal of Chromatography A 1216, 1551 (2009). 3 Papadopoulou S.K., Karapanagiotis I., Zuburtikudis I., Panayiotou C., Journal of Polymer Science Part

B:Polymer Physics 16, 1826 (2010).


107

PI-22: CHARACTERIZATION OF THE VAPOR SORPTION PROPERTIES OF METHACRYLIC AND SILOXANE POLYMERS BY AN OPTICAL METHOD

KYRIAKI MANOLI1, PETROS OIKONOMOY2, DIMITRIS GOUSTOURIDIS2, IOANNIS RAPTIS2, MEROPE SANOPOULOU1.

1 Institute of Physical Chemistry NCSR “Demokritos”, Ag. Paraskevi Attikis, 15310, Athens (Greece)

– [email protected] 2 Institute of Microelectronics, NCSR “Demokritos”, Ag. Paraskevi Attikis, 15310, Athens (Greece)

Abstract

Sorption of VOCs and moisture in thin supported polymer films are important phenomena to a variety of applications, such as coatings, microelectronics manufacturing and chemical sensors. The need for proper material selection according to the intended specific application, has led to implementation of various methodologies for characterizing vapor-induced changes of supported polymer films. In this work a relatively simple methodology based on White Light Reflectance Spectroscopy1 is applied to monitor vapor – induced thickness changes of polymer films, supported on suitable silicon substrates. The measured equilibrium thickness expansion of four methacrylic polymers and two siloxane-based copolymers, exposed to different activities (αs) of water, methanol, ethanol and ethyl acetate vapor, at 30oC, is used to determine the sorption isotherm of each system, assuming unidirectional swelling due to the constraining rigid support.

The deduced sorption isotherms were fitted to the Flory- Huggins equation, by non-linear regression analysis, and interaction parameters χ were determined for each binary system. As an example, the moisture sorption data of all polymers are presented in Fig. 1. The relative sorption capacity of the different classes of polymers towards the four vapors is in line with the expected solubility interactions between solvent and solute. Furthermore, an estimate of the solubility coefficient S, at the limit of infinite dilution, expressed as S= φS /as =exp (-1-χ), is made. The correlation of the values of S to the differences of the Hansen solubility parameters2 Δδ between solute and polymer of each binary system (Fig.2) exhibits a sharp decay of solubility coefficient with increasing Δδ.The results indicate that the applied optical methodology is suitable for screening polymeric materials for specific applications, on the basis of their sorption properties.

Figure 1: Sorption isotherms of Η2Ο vapor in polymer films of thicknesses Lo =197-737nm, at 30 0C (points). Lines represent fitting to the Flory- Huggins equation with interaction parameter χ: 1.58 (PHEMA); 3.73 (PMMA); 4.39 [P(DMS-co-DPhS)-2]; 4.75 (PBMA); 5.11 [P(DMS-co-DPhS)-1];5.36 (PiBMA)

Figure 2: Correlation of solubility coefficients S with three- dimensional solubility parameter differences

1 Manoli, K., Goustouridis, D., Chatzandroulis, S., Raptis, I., Valamontes, E. S., Sanopoulou, M. Polymer 2006,

47, 6117. 2 C. Hansen, Progress in Organic Coatings 2004, 51, (1), 77-84.


108

PI-23: EXPERIMENTAL AND THEORETICAL STUDY OF THE RELEASE KINETICS OF DIPHYLLINE FROM SWELLING POLY (VINYL ALCOHOL)

MATRICES ALBANA HASIMI1,2, KYRIAKI PAPADOKOSTAKI1, MEROPE. SANOPOULOU1

1Institute of Physical Chemistry, NCSR “Demokritos”, 15310 Ag. Paraskevi Attikis, Athens,(Greece) 2 Department of Pharmacy, University “Kristal”, P.O.Box 1521; Tirana (Albania)

[email protected]

Abstract The performance of a model monolithic controlled release device, consisting of a swellable polymeric matrix (polyvinyl alcohol–PVA) subject to structural relaxation, loaded with a hydrophilic drug (diphylline) and activated by the ingress of water, was studied experimentally and by computer simulation. PVA is a glassy polymer with low toxicity, biocompatibility and a wide range of biomedical applications. The system under consideration falls into the class of monolithic controlled release systems which despite their wide use suffer from a continuously declining release rate1. On the other hand, constant release rate can be approached, in principle, when water ingress from the aqueous environment (1) occurs in comparable rate with drug release and/or (2) is controlled by relaxation of the swelling polymer matrix. The kinetic behavior of the system PVA–H2O–diphylline is studied within the framework of a theoretical model, previously developed in our lab2, which can simulate realistically the strong interacting fluxes of invading water and released solute. From the experimental water uptake kinetic data in conjunction with a model for non-Fickian kinetics in glassy polymers3, the transport properties of water in PVA films (diffusion coefficient and relaxation constant) were deduced,4 to be used as input parameters in computer simulation of the drug release process. The release kinetics of diphylline from dry matrices was studied at drug loadings 1–40 % by wt (Fig. 1). In all cases, the release rate remains constant for a prolonged time period, as expected, because the solute release occurs at comparable time scales with the ingress of water in the matrix (Fig. 2).

The relevant input model parameters for the system PVA–H2O–diphylline were derived from independent experimental measurements of the sorption and diffusion properties of water (see above) and solute. The resulting simulation was highly successful, considering that it proved possible to simulate closely and consistently the kinetics of both drug release (over practically the whole experimental range) and concurrent water uptake (Fig. 2). The results presented here are of obvious practical significance in relation to progress towards computer-assisted optimization of the design of swelling-controlled release devices exhibiting relatively complex kinetic behavior.

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Fig.2 Comparison of representative experimental water uptake and concurrent drug release kinetics from dry PVA with model calculations.

1 D.L.Wise, Handbook of Pharmaceutical Controlled Release Technology Marcel Dekker, New York (2000). 2 K.G. Papadokostaki, A. Ya. Polishchuk, J.K. Petrou, J. Polymer Sci.: Polymer Phys. 2002, 40, 1171-1188. 3 J.H. Petropoulos, J. Polymer Sci.: Polymer Phys. Ed. 1984, 22, 1885-1900. 4 A. Hasimi, A. Stavropoulou, K.G. Papadokostaki, M. Sanopoulou, Eur. Polym. J. 2008, 44, 4098-4107.


109

PI-24: FROM ATOMISTIC TRAJECTORIES TO PRIMITIVE PATHS TO THE REPTATION THEORY: TOPOLOGICAL AND DYNAMICAL MAPPING OF MOLECULAR DYNAMICS SIMULATION DATA ONTO THE TUBE MODEL

CHUNGGI BAIG, PAVLOS S. STEPHANOU, GEORGIA TSOLOU , VLASIS G. MAVRANTZAS Department of Chemical Engineering, University of Patras & FORTH-ICE/HT, Patras, GR 26504,

(Greece) - [email protected]

Abstract

We present a computational methodology1 that allows one to map atomistic trajectories of entangled polymer melts accumulated in the course of long molecular dynamics (MD) simulations onto trajectories of primitive paths (PPs) thereby establishing a connection with the tube model of the reptation theory. The mapping is realized by geometrically constructing the effective tube around each primitive chain and then documenting chain motion in terms of a curvilinear diffusion inside the effective tube around the coarse-grained chain contour. The outcome of such a link between atomistic trajectories and tube model is the calculation of the function ψ(s,t), namely the probability that a segment s of the primitive chain remains inside the initial tube after a time t. Linear viscoelastic properties (such as the zero shear rate viscosity and the spectra of storage and loss moduli) obtained on the basis of the obtained ψ(s,t) curves for three different polymer melts (polyethylene, cis-1,4-polybutadiene and trans-1,4-polybutadiene) are in agreement with experimental rheological data. Extensions2 of the methodology to model bidisperse melts of linear cis-1,4-polybutadiene composed of probe and matrix chains show that: a) the values of the static topological properties of the probe chains (average value of their PP contour length and its fluctuation) remain unaltered in the different matrices, but b) their dynamical properties (including ψ(s,t) and its average Ψ(t) over all segments s, the time autocorrelation function of the PP contour length, and the time autocorrelation function of the chain end-to-end vector) vary significantly from matrix to matrix. More precisely, our direct computational study verifies that constraint release (CR) is the dominant relaxation mechanism in binary melts of long and short cis-1,4-polybutadiene chains accounting for the majority of differences observed in their relaxation dynamics in different environments; as a result, CR has a profound effect on their linear viscoelastic properties, such as the spectra of storage and loss moduli. Contour length fluctuations (CLFs), on the other hand, are found to play a secondary role (except for segments near chain ends) and remain practically unaffected by compositional differences. How the simulation results compare with laboratory measurements already reported in the literature on the same or similar systems is also going to be discussed.

1 P.S. Stephanou, C. Baig, G. Tsolou, V.G. Mavrantzas, M. Kröger, J. Chem. Phys. 132, 124904 (2010). 2 C. Baig, P.S. Stephanou, G. Tsolou, V.G. Mavrantzas, M. Kröger, Macromolecules, in press (2010).


110

PI-25: MELT STRUCTURE AND DYNAMICS IN MELTS OF UNENTANGLED POLYETHYLENE RINGS: ROUSE THEORY, ATOMISTIC MOLECULAR

DYNAMICS SIMULATION, AND COMPARISON WITH THE LINEAR ANALOGUES

GEORGIA TSOLOU, NIKOS STRATIKIS, CHUNGGI BAIG, PAVLOS S. STEPHANOU, VLASIS G.

MAVRANTZAS

Department of Chemical Engineering, University of Patras & FORTH-ICE/HT, Patras, GR 26504, (Greece) - [email protected]

Abstract

Motivated by recently reported experimental data1 on the peculiar rheological behaviour of polymer rings, we have undertaken a systematic and detailed study of the structural and mainly dynamical and rheological properties of model ring polyethylene (PE) melts, ranging in molecular length from N=24 up to N=400 carbon atoms per molecule [C24, C400] with the help of atomistic Molecular Dynamics (MD) simulations at temperature T=450K and pressure P=1atm.2 We present simulation results for these systems with respect to the following properties: chain conformation, pair correlation function, intrinsic molecular shape, local dynamics, segmental mean square displacement (msd), self-diffusion coefficient DG, terminal relaxation time τd, spectrum of relaxation times τp, and dynamic structure factor S(q,t). In a second step, by mapping the atomistic MD data onto a modified version of the Rouse model appropriate for ring polymer architectures, we have extracted the monomeric friction coefficient ζ and the zero-shear rate viscosity η0 of the simulated systems. In agreement with previous theoretical3 and experimental studies,4 our MD simulation results support that the structure of a ring polymer in its molten state is significantly more compact compared to the linear analogue due to the imposed topological restrictions during (e.g., nonconcatenation). The simulation results for the intermolecular mer-mer and center-of-mass pair distribution functions confirm that the effective correlation hole is deeper in rings than in linear polymers. The Rouse theory is found to provide a satisfactory description of the rheological behavior of the simulated rings, especially for chain lengths N between 50 and 170 carbon atoms. Furthermore, the dependence of DG, τp, ζ, and η0 on chain length suggests that all the ring PE melts examined in our study follow the scalings of the Rouse theory satisfactorily well; this is true even for the C400 ring PE melt which is significantly longer than the known crossover chain length (~C156) from Rouse to reptation for linear PE melts.

1M. Kapnistos, M. Lang, D. Vlassopoulos, W. Pyckhout-Hintzen, D. Richter, D. Cho, T. Chang, M. Rubinstein, Nature Materials 7, 997 (2008). 2 G. Tsolou, N. Stratikis, C. Baig, P.S. Stephanou, V.G. Mavrantzas, Macromolecules, submitted (2010). 3 B. H. Zimm and W. H. Stockmayer, J. Chem. Phys. 17, 1301 (1949). 4 V. S. Arrighi, S. Gagliardi, A. C. Dagger, J. A. Semlyen, J. S. Higgins, M.J Shenton, Macromolecules 37, 8057 (2004).


111

PI-26: FROM RODS TO RANDOM WALKS: ONSET OF ENTANGLEMENTS REVISITED

CHRISTOS TZOUMANEKAS1,2, F. LAHMAR3, B. ROUSSEAU3 , D. N. THEODOROU1,2

1 Department of Materials Science and Engineering, School of Chemical Engineering, National Technical University of Athens, Zografou Campus, 15780 Athens (Greece) – [email protected] 2 Dutch Polymer Institute (DPI), P.O. Box 902, 5600 AX Eindhoven (The Netherlands) 3 Laboratoire de Chimie Physique, UMR 8000 CNRS, Bâtiment 349, Université Paris-Sud 11, 91405 Orsay Cedex (France)

Abstract

Onset of entanglements is usually described as a crossover in the dynamical and rheological properties of a polymer melt, for example in a plot of the zero shear rate viscosity as a function of molecular weight. The crossover length is the critical molecular weight, Mc. Macroscopic or microscopic evidence for a corresponding structural (or static) crossover doesn’t exist. Statically, entanglement is quantified by the entanglement molecular weight, Me, which determines the degree of entanglement of a long-chain polymer system. However, Me is not described as a crossover length. Moreover, it has long been known that the variation of density and stiffness between different species signifies changes in the degree of entanglement of polymer melts. An overlooked point is that, as chain length N increases, the contour length density (or mass density), and the stiffness of the system (or characteristic ratio), increase, until they reach chain length-independent values (large N regime). We show1 that the variation of these quantities, as chain length increases, controls also the onset of entanglements. A static crossover exists, but at a coarse grained level. The crossover length is Me. Our analysis is based on the reduction of Dissipative Particle Dynamics trajectories of a polymer melt to Primitive Paths (PPs). The latter are generated by using the CReTA algorithm, which constructs PPs by reducing chain conformations to the corresponding shortest paths. As N increases, the N-dependence of density and stiffness control the N-variation of chain overlap. The latter shows a stronger N-dependence in the short than in the long-chain regime, and for large N it falls gradually to the scaling law expected of long-chain systems. At the level of PPs, the increasing overlap leads to a crossover in the system topology which can be described as a gradual transformation of PP conformations from thin rods (short chains), to random walks (long chains), A simple scaling model predicts that this transformation leads to a Rouse to reptation transition in dynamics and rheology. The entanglement molecular weight (MW) is interpreted as the crossover length of this transition. The predicted Mc /Me ratio is one, which, though small, is compatible with packing length independence and the suppression of contour length fluctuations within the model. The comparison between a dynamical and a static topological analysis reveals a slowing down of Rouse modes, which is maximum at the length scale where the underlying system of PPs appears as a network of topological constraints.

1 Macromolecules 42 7474 (2009) ; Macromolecules 42 7485 (2009)


112

PI-27: BROWNIAN DYNAMICS SIMULATIONS ON SELF-ASSEMBLY BEHAVIOR OF H-SHAPED COPOLYMERS AND TERPOLYMERS.

OTHONAS MOULTOS, LEONIDAS N. GERGIDIS AND COSTAS VLAHOS

Department of Chemistry, University of Ioannina, 45110 Ioannina, Greece

Abstract

The micellization behavior of the H-shaped copolymers1 and terpolymers2 is studied by means of Brownian dynamics simulations. The critical micelle concentration, the micelle size distribution and the shape of micelles are examined as a function of the mass fraction of the solvophobic units. Three regimes were found. H-shaped copolymers with solvophobic content ≥ 50% form micelles with preferential aggregation number. Those with content << 10% do not aggregate at the simulation temperature. For the remaining content values the formation of micelles exhibits a wide variation of aggregation numbers. These regimes are in qualitative agreement with experiment. H-shaped terpolymers form micelles with larger aggregation number than the respective H-shaped copolymers. Janus-like micelles or micelles with multi-compartment coronas are obtained.

a) b) Figure 1. Mass distribution of the aggregates for various H-Shaped copolymers a) Aggregates following a bell-shaped distribution and b) Aggregates following a non-bell-shaped distribution.

Figure 2. Mass distribution of the aggregates for H-Shaped terpolymers (A8)2B30(C8)2 for different Lennard-Jones interactions parameters (εAC).

Janus-like micelle with aggregation number 3.

1 Iatrou, H.; Willner, L.; Hadjichristidis, N.; Halperin, A.; Richter, D. Macromolecules 1996, 29, 581- 591. 2 Christodoulou, S.; Driva, P.; Iatrou, H.; Hadjichristidis, N. Macromolecules 2008, 41, 2607-2615.


113

PI-28: A MOLECULAR DYNAMICS SIMULATION STUDY ON SI-RNA/TEA-PAMAM DENDRIMER COMPLEXATION

KOSTAS KARATASOS1,2, SABRINA PRICL2 , PAOLA POSOCCO2 AND ERIK LAURINI 1Chemical Engineering Department, Aristotle University of Thessaloniki, University Campus, 54124,

Thessaloniki (Greece) – [email protected] 2 MOSE-DMRN, University of Trieste, Piazzale Europa 1, 34127 Trieste, (Italy) -

[email protected], [email protected], [email protected]

Abstract

In this work we report results from fully atomistic models of triethanolimine (TEA) Poly (amidoamine) dendrimers of different generations, at experimentally realizable conditions. Our aim was to gain a deeper insight on the mechanisms promoting the observed formation of stable complexes between this type of flexible-core TEA-PAMAM dendrimers and short interfering RNA (siRNA). These complexes were found to comprise a particular promising class of siRNA deliver for gene-silencing purposes1-2. To elucidate the key reasons for their favorable binding affinity with siRNA, we have examined in detail pertinent static/conformational features as well as specifics related to hydrogen-bond formation between the dendrimer and siRNA moieties. The results were compared to the behavior of complexes comprised by commercial NH3-cored PAMAM dendrimer analogues, in order to distinguish potentially important factors that might differentiate the complex-formation characteristics between these two categories of complexes. REFERENCES (1) Zhou, J.; Wu, J.; Hafdi, N.; Behr, J.; Erbacher, P.; Peng, L. Chem Commun (Camb) 2006, 2362 (2) Liu, X. X.; Rocchi, P.; Qu, F. Q.; Zheng, S. Q.; Liang, Z. C.; Gleave, M.; Iovanna, J.; Peng, L. Chemmedchem 2009, 4, 1302.


114

PI-29 :YIELDING OF COLLOIDAL GLASS UNDER LARGE AMPLITUDE OSCILLATORY SHEAR1

ANDREAS S. POULOS1, FREDERIC RENOU1, NIKOS KOUMAKIS1, JORG STELLBRINK2, GEORGE PETEKIDIS1

1Institute of Electronic Structure and Laser, FORTH, 70013 Heraklion (Greece) – [email protected]

2Institute für Festkörperforschung, FZ Jülich, Julich, Germany

Abstract

The understanding of yielding and flow of a colloidal glass under large amplitude oscillatory shear (LAOS) represents a motivating challenge. Monitoring the higher harmonics in the stress signal by Fourier-Transform (FT) rheology may provide useful insight on the progressive transition from linear to nonlinear viscoelastic response and the mechanisms involved during shear induced melting. Here we study the process of yielding in a colloidal glass formed of star-like micelles with LAOS and interrogate the nonlinear intracycle stress response by FT analysis2 and decomposition to an orthogonal set of Chebyshev polynomials3. Such approach provides a robust framework enabling us to map out a rich phenomenology of intracycle nonlinearities that may relate to distinct physical mechanisms. We find that the nonlinearities during yielding are represented in the form of intracycle shear-thickening/thinning and strain-hardening/softening in the viscous and elastic response respectively (fig.1). We argue that the underlying mechanisms are cage breaking and reformation as well as stress storing and relaxation within the period of oscillatory shear which are affected by an interplay between shear and Brownian motion. Finally, to access the influence of the polymeric arm interpenetration and the soft interparticle potential of such star-like micelles we compare their response with that of hard sphere glasses.

Figure 1: (left) Dynamic strain sweeps of star-like micelle samples at different temperatures. The shear induced melting of the glass can be seen for large strain amplitudes at all temperatures. (right) Phase angle between the third stress harmonic and the strain as a function of the amplitude of oscillation. As the amplitude is increased, the leading nonlinear contributions show a progression from a shear thickening to a strain hardening and finally to a shear thinning behaviour.

1 Renou, F., Stellbrink J., Petekidis G. (2010) Submitted. 2 Wilhelm, M., D. Maring, et al. (1998). "Fourier-transform rheology." Rheol. Acta 37: 399-405. 3 Ewoldt, R. H., A. E. Hosoi, et al. (2008). "New measures for characterizing nonlinear viscoelasticity in large amplitude oscillatory shear." J. Rheol. 52(6): 1427-1458.


115

PI-30: STRUCTURE AND DYNAMICS IN SUSPENSIONS OF SOFT COLLOIDS

ANDREAS PAMVOUXOGLOU 1, 2,+ AND GEORGE PETEKIDIS 1, 2,*

1FORTH/ Institute of Electronic Structure and Laser, P.O Box 1527, 71110 Heraklion, Greece 2Department of Materials Science and Technology, University of Crete, Heraklion, Greece

[email protected] , *[email protected]

Abstract

The structure and dynamics of core-shell particles with a hard inorganic core and a PMMA

shell [1] were studied by 3D Dynamic Light Scattering to suppress multiple scattering effects. The data were interpreted through comparison with hard, permeable and charged spheres. By changing the molecular weight of the PMMA chain and/or solvent we can tune the softness of the particles. Due to this softness, the crystal phase is wider and the particles mainly form an FCC crystal . In this work we studied two systems with the same core size and grafting density, but different chain length (Mw ~126k and 402k).

It was found that the structure factor is affected by the chain length. For the small particles the first peak position of the S(Q) follows a φ-1/3 dependence, similar to what is expected for charged spheres . On the other hand larger particles show longer ranged repulsive interactions, deviating from the behavior of the small.

The q-dependence diffusion coefficient D(Q) shows a slow down of the dynamics at the peak of S(Q) for both systems. The short-time self diffussion cofficient Ds(Q) of the small particle extracted at high Q’s, follows simulation predictions for hard spheres, whereas for the large ones with longer polymeric chains, experimental data deviate from hard sphere prediction. The dynamic properties at the minimum of D(Q), which are strongly affected by the hydrodynamic interactions cannot be described by any theoritical prediction currently avaiable, suggesting a distinct effect of the long polymeric chains in the hydrodynamic interactions.

1 In collaboration with: Kohji Ohno, Institute of Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan

1. Ohno, K., et al., Suspensions of Silica Particles Grafted with Concentrated Polymer Brush: A New Family of Colloidal Crystals. 2006. p. 1245-1249.


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PI-31: FRICTION WELDING OF PLASTIC PIPES: MONITORING OF PROCESS PARAMETERS AND QUALITY EVALUATION OF THE JOINT SECTION VIA

PULL-OUT TESTS AND MICROTOMOGRAPHY SOUZANNA SOFOU1,ELIAS PSIMOLOFITIS1, PANAYIOTIS PHILIMIS1, HARIS DOUMANIDIS2

1 CNE Technology Center, Democratias 5, Ergates Industrial Estate, 2643 Ergates (Cyprus) –[email protected]

2Department of Mechanical and Manufacturing Engineering, University of Cyprus, P.O. Box 20537, 1678 Nicosia (Cyprus)

Abstract

The production and use of plastic pipes has rapidly increased during the last years, due to their low production, processing and maintenance cost. However, an important cost associated to their use is the cost of joining them. The main methods for joining plastic pipes are i) the use of mechanical joints which are expensive ii) electrofusion, which is known to have a high rate of failures and iii) butt welding, which is time consuming. Moreover, each method is limited to specific applications and there is no reliable non destructive tool that can be used for the joint quality evaluation on a pass/fail basis.

Friction welding (FW) is a well established technique for joining plastic pipes at the experimental level. However, the process is vastly underutilized in the plastics sector, mainly due to the joint and tooling design complexity, which limits its use for site applications and repairs. In a former research project, CNE and its partners1 have developed a prototype experimental FW machine for medium-size diameter (50-110mm) plastic pipes. The FW technique has a novel configuration using a specially designed collar and sleeve, which joints the pipe ends. This work verified the strong advantages of FW: it is one of the least sensitive processes with respect to changes in the materials chemistry2, the welding time and the energy consumption is smaller than other methods3,4,5, and can be used to join similar/dissimilar materials6,7. In this work, a control system (National Instruments SCXI 1600) and a LabView program developed for this experimental series are used for the study of the FW process parameters, for three different collar geometries. Results give the Axial Force (applied Pressure) and the Temperature as a function of time. Temperature is measured on the external and internal surface of the PE pipes, by use of Infrared Sensors (IR) and Thermocouples (TC), respectively. A constant temperature difference (TC 2-IR) was noticed, which practically means that welding quality could, in the future, only be assessed by the use of Infrared Sensors. Weld Quality is initially evaluated by testing the joints’ resistance to pull out, as done for fittings (ISO 14236:2000). The three joints showed different resistance to pull out when submitted to the predefined longitudinal tension. Furthermore, a SKYSCAN 1074 Micro-CT Scanner is used in order to evaluate welding quality by use of microtomography. Pressure tests are also necessary in order to perform a more elaborate quality evaluation of the joints. Such work is currently under way by the authors.

1 CNE Technology Center, “Development of a Portable Friction Welding Machine for Plastic Pipes”, Research Promotion Foundation of Cyprus, ΤΕCHΝΟ/0104/14 (2007). 2 Lei, Y.P. and Shi, Y.W., “On a Model for Estimating the Interfacial Contaminant Expelling Rate in Friction Welding of Tubular Form”, Journal of Material Processing Technology, 44, 265-272 (1994). 3 Neitzel, M., et al. “Friction welding for plastic pipe in the chemical industry”, Welding in the World, 19, No.5/6, 67-79 (1981). 4 Stafford, T.G., “The Welding of Plastic Pipe”, Joining Plastic in Production, 135-145 (1988). 5 Tappe, P. and Potente, H., “New Findings in the Spin Welding of Plastics”, ANTEC Conf. Proc. SPE, (1989). 6 Crawford, R.J. and Tam, Y., “Friction Welding of Plastics”, J. of Materials Science, 16, 3275-3282 (1981). 7 Lin, C.B. and Wu, L.C., “Friction Welding of Similar and Dissimilar Materials: PMMA and PVC”, Polymer Engineering and Science, 40, No 8, 1931-1941 (2000).


117

PI-32: IMIDAZOLE BEARING AROMATIC POLYETHERS TARGETING HIGH TEMPERATURE PEM-FC APPLICATIONS

AIKATERINI ANDREOPOULOU1,2, GEORGE DRAKOS1, MARIA DALETOU2 1Department of Chemistry, University of Patras, GR-26500 Rio-Patras, Greece –

[email protected],gr 2Institute of Chemical Engineering and High Temperature Chemical Processes, ICE/HT-FORTH, Post

Office Box 1414, GR-26504 Rio-Patras, Greece

Abstract

The research for new polymeric materials that fulfil all the prerequisites for applications in high temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) is of utmost importance due to the advantages that this operation offers over the conventional fuel cells operating at temperatures up to 80oC (LT-PEMFCs). On the other hand, due to the harsh chemical conditions existing in the former case, only few polymeric materials can efficiently withstand. Up to now polybenzimidazole is the state of the art material,1 but it needs high doping levels to give highly conductive membranes while the oxidative stability of the membranes is moderate. An alternative approach is based on the use of pyridine containing aromatic polyethers that give membranes with ionic conductivities in the range of 10-2 S/cm even for lower doping levels and at the same time the oxidative and thermal stability of the membranes are exceptionally good2,3. In this work, imidazole bearing monomers are introduced into polyether backbones in an effort to combine the advantages of polyether chains and imidazole units. Thus, new aromatic co-polyethers containing main chain pyridine-imidazole or side chain imidazole moieties have been synthesized. Soluble copolymers were obtained in cases where the imidazole monomers were combined with alkyl-substituted diols, like bisphenol A or tetramethyl biphenol, or when low imidazole ratios were employed. Various copolymer compositions were synthesized and tested in order to obtain the influence of the structural parameters on solubility. The copolymer compositions which show good film forming properties were further characterized in respect to their mechanical properties and thermal transition temperatures as well as their ability to absorb strong protic acids like phosphoric acid, as a prerequisite to give ionically conducting membranes which can be used in HT-PEMFCs.

Acknowledgement: Financial support of this work from the European Commission through the programs NMP3 CT-2006-033228 (2006-2009) and IRAFC FCH-JU 245202 (2010–2012) is acknowledged. 1 J. Mader, L. Xiao, T. J. Schmidt, B. C. Benicewicz, Polybenzimidazole/Acid Complexes as High Temperature Membranes, In Fuel Cells II: Adv. Polym. Sci. 2008, 216, 63-124, Vol. Ed: G. G. Scherer, Springer-Verlag Berlin 2008. 2 E. K. Pefkianakis, V. Deimede, M. K. Daletou, N. Gourdoupi, J. K. Kallitsis, Macromol. Rapid Commun. 2005, 26, 1724–1728. 3 J. K. Kallitsis, M. Geormezi, S. G. Neophytides, Polym. Int. 2009, 58, 1226–1233.


118

PI-33: ON THE CRYSTALLINITY AND CHAIN CONFORMATIONS IN PEO / LAYERED SILICATE NANOCOMPOSITES

KONSTANTINOS ANDRIKOPOULOS1, KIRIAKI CHRISSOPOULOU2, STAVROS BOLLAS2, SAPFO FOTIADOU2,3, GEORGE VOYIATZIS4, SPIROS H. ANASTASIADIS2,5

1 Physics Division, School of Technology, Aristotle University of Thessaloniki, Thessaloniki, (Greece)[email protected]

2Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas, P.O. Box 1527, 711 10, Heraklion, Crete (Greece)

3 Department of Chemical Engineering, Aristotle University of Thessaloniki, Thessaloniki (Greece) 4 Institute of Chemical Engineering and High Temperature Chemical Processes, Foundation for

Research and Technology-Hellas, P.O. Box 1414 Patras (Greece) 5Department of Chemistry, University of Crete, P.O. Box 2208, 710 03 Heraklion Crete (Greece)

Abstract

Polymer / layered silicate nanocomposites constitute an interesting class of materials which allow the investigation of basic scientific problems and at the same time are utilized in many applications. Mixing polymers with layered inorganic materials can lead to three types of structure, depending on the interactions between the two components: the phase separated, where the two components are immiscible, the intercalated, in which the polymer chains reside within the inorganic galleries forming thin polymer films, and the exfoliated one where the interactions between the chains and the surfaces are very favorable that the inorganic layered structure is destroyed resulting in dispersed platelets within the polymer matrix. Despite the large number of studies in this area, the influence of the addition and the state of dispersion of the nanofillers on the conformation of the chains and/or on the crystallization has been largely overlooked.

2800 3000

30%

100%

98%

95%

90%

65%

80%

PEO

800 1000 1200 1400

Raman Shift [cm-1]

Inte

nsity

[arb

. uni

ts]

Figure 1: Raman spectra of PEO and of PEO / Na+-MMT nanocomposites with different polymer concentrations at ambient temperature.

We aim to systematically study the effect of incorporation of inorganic material and/or elucidate the influence of the severe confinement on the structure and conformations of polymer chains in PEO / Na+-MMT nanohybrids. A series of composites with PEO content that covers the whole regime from pure polymer to pure clay was utilized and characterized by X-ray diffraction and differential scanning calorimetry. In all cases, intercalated nanocomposites with mono- and bi-layers of PEO chains were obtained. We show that for low polymer concentrations where all the polymer chains are intercalated, or close to the inorganic surfaces, PEO is purely amorphous and it is only when there is plenty of excess polymer outside the full galleries that the bulk polymer crystallinity is recovered. Raman and infrared spectroscopies have been applied to obtain information on the conformation of the polymer chains in the hybrid material in relation to that of pure PEO. Figure 1 shows Raman measurements of a series of nanohybrids with different compositions that, in agreement with XRD and DSC show that it is only when there is a high polymer content that the sharp peaks attributed to crystalline PEO are observed. These studies can facilitate the extraction of information related to the chain conformations in the vicinity of the inorganic interfaces.


119

PI-34: CRYSTALLIZATION KINETICS IN POLYMER / LAYERED SILICATE NANOCOMPOSITES

KIRIAKI CHRISSOPOULOU1, HELLEN PAPANANOU1,2, ELENI PAVLOPOULOU1, GIUSEPPE PORTALE3, WIM BRAS3, SPIROS H. ANASTASIADIS1,4

1Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas, P.O. Box 1527, 111 10 Heraklion, Crete (Greece) – [email protected]

2Department of Chemical Engineering, Aristotle University of Thessaloniki, 541 24 Thessaloniki (Greece)

3ESRF, DUBBLE CRG, Netherlands Organization for Scientific Research (NWO), Grenoble (France) 4Department of Chemistry, University of Crete, 710 03 Heraklion Crete (Greece)

Abstract

Polymer crystallization has been a widely studied subject and is still a very interesting topic since it determines the final properties of these technologically and scientifically exciting materials. There is a hierarchy in the formation of a polymer crystal with the repetition of the unit cells forming the polymer crystallites which sequentially form what is called spherulites. The complete characterization of polymer crystallization requires a different characterization technique for each hierarchical step, due to the different length-scales involved. On the other hand, addition of inorganic nanomaterials and more specifically of layered silicates, has been recently widely used to optimize polymer properties. Nevertheless, despite the fact that the desired intercalated or exfoliated structure has been frequently achieved and the improvement of mechanical, thermal, flammability or barrier properties has been reported, the behavior has not been fully understood. Moreover, in the case of semi-crystalline polymers, the influence of the addition and the state of dispersion of the nanofillers on the total crystallinity as well as on the crystallization kinetics and characteristics has been largely overlooked.

0.0 0.2 0.4 0.6 0.8 1.0 1.20.0

1.0x10-9

2.0x10-9

3.0x10-9

4.0x10-9

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6.0x10-9

I*q2

q (nm-1)

90% PEO + 10% Na+MMTisothermal crystallization at 47oC

q*

800 1200 1600 2000 24000

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4

6

8

10

Hea

t Flo

w (m

cal/s

)

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45 46 47 48 49 50 51 52 53 54 57

99% PEO + 1% Na+MMT

Figure 1: Lorentz representation of the SAXS intensity of a PEO nanohybrid at 47°C

Figure 2: Isothermal DSC measurements of a PEO hybrid at different crystallization temperatures

In this work, the structure, morphology and crystallization behavior of a hydrophilic, crystalline polymer, poly(ethylene oxide), PEO, when mixed with natural montmorillonite (Na+-MMT) are investigated in a range of compositions that covers the whole regime from pure polymer to pure clay. The structure of the hybrids was investigated over multiple length scales by X-ray diffraction, Polarizing Optical Microscopy (POM), Small Angle X-ray Scattering (SAXS) (Figure 1) as well as Differential Scanning Calorimetry (DSC) (Figure 2). The time resolved measurements reveal the effect of clay on crystallization. Even very small amount of the inorganic can cause a significant decrease of the spherulite size and an increase of the spherulite number whereas it affects their radius growth. Moreover, a change is found in the crystallization mechanism from sporadic nucleation for pure PEO to two-dimensional growth with predetermined nuclei for low clay concentration. Acknowledgements: Part of this research was sponsored by the Greek General Secretariat for Research and Technology (Programme ΠΕΝΕΔ 03ΕΔ581)


120

PI-35: COLLAPSE TRANSITIONS IN THERMOSENSITIVE MULTI-BLOCK COPOLYMERS: A MONTE CARLO STUDY

ANASTASSIA N. RISSANOU1, EVANGELOS MANIAS2, IOANNIS A. BITSANIS1 1Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas,

P.O. Box 1527, 711 10 Heraklion Crete,( Greece) – [email protected] 2Department of Materials Science & Eng., Pennsylvania State University, University Park, PA, (USA).

Abstract Multi-block copolymers are expected to exhibit a rich transition behavior in selective solvents. This behavior has implications in life sciences and applications to the design and material selection of thermo and pH-sensitive materials and membranes. We have studied the transitions of model alternating copolymers via Monte Carlo (MC) simulations. Copolymers of the type (AAA…)n1(BBB…)n2(AAA…)n1(BBB…)n2… with blocks A and B chemically connected were simulated. In this work we study single chains of multi-block copolymer chains in selective solvents. Our results demonstrated that the most important factor, which controls block copolymer response to external stimuli, is their chemical composition (i.e., the thermodynamic competition of the sequential blocks). We focused on the extreme case of a single polymer chain of N = 1000 units, distributed in alternate blocks of n1= n2 =100 units (A- and B- blocks). The solvent was quite selective, i.e. A-blocks (500 units) were soluble EAA = 0.10kT (good solvent, almost athermal) whereas, the B-blocks (500 units) were quite insoluble EBB = 0.45 (poor solvent)1. In this case an extended critical region was observed, characterized by the presence of several distinct intermediate states between coil and globules, and by fluctuation strong enough to induce spontaneous transitions between these states. Figure 1 depicts typical conformations of multi-block copolymers of high frequency of appearance and with different number of globules.

Fig.1 Conformations with three, two and one globules from left to right.

Our findings underline that, even in a case of very high blockiness, the alternating architecture introduces qualitatively new phenomena. In particular, the collapse transition proceeds through stages not existing in the corresponding homopolymer and di-block copolymer transition.

1 A. N. Rissanou, S. H. Anastasiadis, I. A. Bitsanis, Journal of Polymer Science: Part B, 44, 3651–3666 (2006).


121

PI-36: INFLUENCE OF MOLECULAR ARCHITECTURE ON THE PROPERTIES OF POLYMER THIN FILMS

EMMANOUIL GLYNOS1, BRADLEY FRIEBERG2, HYUNJOON OH1, MING LIU3, DAVID W.

GIDLEY3 AND PETER F. GREEN1 1Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan

48109, USA 2Macromolecular Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA

3Department of Physics, University of Michigan, Ann Arbor, Michigan, USA

Abstract

Polymer films play an increasingly important role in a diverse range of technological applications: coatings, displays, organic electronics, etc. The role of thickness confinement on the properties of thin polymer films has garnered widespread interest from researchers in various communities, in recent years. Experiments have revealed that thin films of linear chain polymers exhibit thickness dependent behavior in their glass transition, Tg, and their dynamics when the thickness of the films (H) is a few tens of nanometers or thinner, reflecting consequences of confinement and, more importantly, the strength of interactions of macromolecules with the external interfaces. For weak, non-wetting, interactions between the polymer segments and substrates, the average Tg of the film decreases with decreasing H, Tg<0, as observed for example in numerous experiments for polystyrene (PS) supported by silicon oxide substrates. When the interactions between the chain segments and the substrate are particularly strong (e.g.: hydrogen bonding), the Tg increases with decreasing H, as observed for poly(methyl methacryalte) (PMMA) supported by silicon oxide substrates. In light of these effects, which are largely associated with interfacial processes, the natural question would be how molecular architecture might affect the virtification behavior of polymers subjected to thickness constraints? We show that effects primarily associated with the architecture of polymeric molecules can have a profound effect on the properties, such as Tg, of thin supported films. Specifically, star-shaped molecules, possessing sufficiently high functionality and sort arm, exhibit significant differences in virtification, both in magnitude and the thickness dependent trends, from their linear analogues. These findings have implication for other properties, due largely the origin (entropic) of this behavior


122

PI-37: SELF ASSEMBLY AND MORPHOLOGY OF PH-SENSITIVE HETEROARM STAR BLOCK TERPOLYMERS IN AQUEOUS MEDIA

ZACHAROULA IATRIDI1, CONSTANTINOS TSITSILIANIS1,2 1Department of Chemical Engineering, University of Patras, 26504, Patras (Greece) –

[email protected], [email protected]

2 Institute of Chemical Engineering and High Temperature Chemical Processes, ICE/HT-FORTH, P.O. Box 1414, 26504 Patras (Greece)

Abstract

An amphiphilic An(B-b-C)n heteroarm star block terpolymer bearing the hydrophobic polystyrene (PS) and the pH-dependent poly(2-vinyl pyridine)-b-poly(acrylic acid) (P2VP-b-PAA) diblock copolymer arms, (Scheme 1) was synthesized by anionic polymerization, using an extending “in-out” method and a post polymerization deprotection reaction. Three PSn(P2VP-b-PAA)n star terpolymers with different number of arms ‘n’ were studied in dilute aqueous solutions by using electrophoresis (zeta potential), Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM), as a function of pH.

From the zeta potential measurements of the PSn(P2VP-b-PAA)n star terpolymer aqueous solutions, three different pH regions were distinguished. At low and high pH values, the star polymers form positively and negatively micellar nanoparticles respectively. There is an intermediate region where the polymers solutions exhibit an isoelectric point (iep) defining phase separation and precipitation.

Due to the protonation/deprotonation of the pH-sensitive P2VP-b-PAA block-arms, the star terpolymer association is strongly affected by the pH values of the medium. Furthermore, the resulted micellar morphologies were influenced by the molecular characteristics (e.g. number of arms) of the stars, as demonstrated in Scheme 2.

PSn(P2VP-b-PAA)n

Scheme 1. Schematic representation of the PSn(P2VP-b-PAA)n star terpolymers.

Scheme 2. TEM images of a) PS9(P2VP-b-PAA)9 b) PS21(P2VP-b-PAA)21 and c) PS28(P2VP-b-PAA)28 embedded on carbon grids from aqueous dilute solutions (0.007wt %), of pH=2. The scale bars indicate 200 nm.

ca b


123

PI-38: DESIGN OF BLOCK-RANDOM SEGMENTED POLYMERS ZACHAROULA IATRIDI1, GEORGE GOTZAMANIS1 CONSTANTINOS TSITSILIANIS1,2

1Department of Chemical Engineering, University of Patras, 26504, Patras (Greece) – [email protected], [email protected]

2 Institute of Chemical Engineering and High Temperature Chemical Processes,

ICE/HT-FORTH, P.O. Box 1414, 26504 Patras (Greece) – [email protected]

Abstract

Segmented polymers bearing homopolymer and random copolymer building blocks (Scheme 1) designated as block-random polymers have received increasing attention the recent years. Such polymers can be designed through macromolecular engineering by using controlled polymerization methods. Incorporating a random block, instead of a homopolymer one, in block copolymer topologies, provides further tuning of the copolymer properties (i.e. thermo- or pH-sensitivity, hydrophobicity, light-sensitivity, multi-functionality etc). For instance, “smart” nanostructured polymeric micelles that respond to temperature in aqueous environment, require precise control of the Lower Critical Solution Temperature (LCST) of the thermo-sensitive block. This can be achieved by adjusting the composition of a random copolymer block composed of a monomer of a given LCST and a comonomer of specific nature.

Two examples of pH-sensitive block-random terpolymers are presented in this work, dealing with their self assembly in aqueous media: an amphiphilic multi-armed star shaped block terpolymer bearing polyampholyte segments and internal hydrophobic blocks, and a block-random triblock terpolymer. Thanks to the polyampholyte nature of the outer blocks and the high number of arms, the preferable structure of the core[MMA48-b-(DEA31-co-MAA26)]32 star in water, is that of unimolecular micelle with changeable charge density and sign, depending on the pH of the aqueous environment. The PMMA86-b-P(DEA190-co-MAA96)-b-PMMA86 triblock behaves as amphiphilic gelator capable to alter the sign and the charge density of the potential elastic chains of the network, which form in aqueous semi-dilute solution through hydrophobic interactions of the PMMA stickers. This terpolymer exhibits strong swelling ability in acidic as well as in basic conditions, forming transparent free standing reversible hydrogels.


124

PI-39: pH RESPONSIVE REVERSIBLE HYDROGEL / LIPOSOME COMPOSITES FOR TUNNING DRUG RELEASE

MARIA-TEODORA POPESCU1, SPYRIDON MOURTAS2, SOPHIA G. ANTIMISIARIS2,3

CONSTANTINOS TSITSILIANIS1,3

1Department of Chemical Engineering, University of Patras 26504, Patras, Greece 2 Laboratory of Pharmaceutical Technology, Department of Pharmacy, School of Health Sciences,

University of Patras 26504, Patras, Greece 3 Institute of Chemical Engineering and High Temperature Chemical Processes, ICE/HT-FORTH,

P.O. Box 1414, 26504 Patras, Greece

Abstract

In this work, novel hydrogel composites based on stimuli responsive poly (2-vinyl pyridine) -b-poly (acrylic acid)-b-poly-(n-butyl methacrylate) (P2VP58-PAA924-PnBMA48) ABC terpolymer were studied as a matrix for loading drug-in-liposomes formulations. Specifically, liposomes composed of phosphatidylcholine (PC) and Cholesterol, at a 1:1 mole/mole ratio and encapsulating calcein (100mM), as a model hydrophilic drug, were prepared by probe sonication. The terpolymer exhibits a pH-responsive behavior, from core-shell-corona micellar nanoparticles, at low pH, to a three-dimensional network, as the pH is increased above 6 (Figure 1a,b).1,2 This formulation can undergo a closed loop sol-gel-sol transition (Figure 1a), with the formation of a reversible network at physiological pH. The liposomes were dispersed in the terpolymer aqueous solution at low pH, and the composite hydrogel was formed at pH 7.4 by dialysis (Figure 1c). The release of calcein was monitored by means of fluorescence measurements. Results showed that calcein release can be controlled by the gelator concentration, so that slower release can be obtained at higher concentrations (Figure 1d). Thus, the environmental stimuli, such as pH and ionic strength, in addition with the triblock copolymer concentration, can provide multiple controls over the drug release kinetics. Figure 1. (a) Zero-shear viscosity as a function of pH for P2VP58-PAA924-PBMA48 1.5wt.% aqueous solutions at 25 0C, (b) atomic force microscopy (AFM) image of terpolymer flower like micelles incorporated to the 3D network, (c) schematic representation of the pH responsive drug-in-liposome-in-polymeric matrix formulation, (d) cumulative amount of calcein released per time (h) from plain liposomes and liposomal gels at different concentrations.

P2VP-PAA-PnBMA

0 100 200 300 4000

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ge o

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125

PI-40: NANOSTRUCTURED MICELLES FROM SELF-ASSEMBLY OF PεCL-b-PEO-b-P2VP-b-PEO-b-PεCL

PENTABLOCK TERPOLYMERS IN WATER

MYRTO KOROGIANNAKI1,2, MARIA-TEODORA POPESCU1,2 , KATERINA MARIKOU1,2, CONSTANTINOS TSITSILIANIS1,2

1Department of Chemical Engineering, University of Patras, 26504, Patras (Greece)

[email protected] 2 Institute of Chemical Engineering and High Temperature Chemical Processes,

ICE/HT-FORTH, 26504 Patras (Greece)

Abstract The present work deals with the self-assembly of a novel amphiphilic pentablock copolymer,

PεCL46-PEO199-P2VP598-PEO199-PεCL46 consisting of a pH-sensitive poly(2-vinylpyridine) (P2VP), bearing at both ends hydrophilic poly(ethyl oxide) (PEO) biocompatible blocks , end-capped by hydrophobic poly(ε-caprolactone) (PεCL) biodegradable blocks in aqueous media. This type of copolymer exhibits pH-sensitive nanostructured morphologies. Light Scattering (LS) experiments in combination with Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) have been used in order to explore the association behavior of the system. The micelles have been prepared by dissolution in DMF followed by step dialysis in pure water. Results have shown that spherical flower-like micelles (Scheme 1 left) were obtained, at low pH, with a PεCL hydrophobic core stabilized by a PEO shell, surrounded by a positively charged P2VP corona. This behavior is ascribed mainly to the hydrophobic interactions of the PεCL blocks. At high pH, neutral core-shell micelles (Scheme 1 right, Figure 1) were formed, due to additional contribution of the hydrophobic deprotonated P2VP blocks. Due to the topology of the PεCL hydrophobic blocks, bridging of micelles were observed by SEM and TEM at high pH (Figure 1D).

Scheme 1: Schematic representation of the expected micellization of the ABCBA pentablock copolymer in low and high pH.

Figure 1: A, C TEM micrographs, B SEM micrograph, D Schematic illustration of the different kinds of interconnections between two micelles of the PεCL46-PEO199-P2VP598-PEO199-PεCL46 of micellar nanostructures embedded from aqueous solution at pH 7.


126

PI-41: AMPHIPHILIC POLY(ISOPRENE-B-ETHYLENE OXIDE) BLOCK COPOLYMERS CARRYING HYDROXYL/ESTER FUNCTIONALITIES ON THE

POLYISOPRENE BLOCK ELENI KADITI, STERGIOS PISPAS

Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation

48 Vassileos. Constantinou Ave., 116 35 Athens, Greece – [email protected]

Abstract

The ability of amphiphilic block copolymers (AmBC) to self-assemble into ordered structures, when dissolved in aqueous media has attracted extensive research interest in recent years 1 2. Micellar aggregates formed by AmBC are characterized by their unique core-shell architecture, where in an aqueous environment the hydrophobic blocks of the copolymer are segregated from the aqueous exterior to form the inner core, and the hydrophilic blocks form the corona or the outer shell. Such self-assembled nanostructures have found a range of applications, especially in drug encapsulation and delivery3. In these systems encapsulation properties can be tuned via judicious chemical modification of the core segments 4 In this work hydroxyl/ester functionalized amphiphilic block copolymers were synthesized from poly(isoprene-b-ethylene oxide) diblock copolymer precursors, prepared by anionic polymerization high vacuum techniques, via reaction of the polyisoprene block with formic acid, hydrogen peroxide and acetic anhydride. The characteristic groups of copolymers and the degree of functionalization were identified by utilization of FTIR and NMR spectroscopies. The results show that the PI block is partially modified by -ΟΗ and -ΟCOCH3 groups. In addition, differential scanning calorimetry (DSC) measurements showed that the crystallization of PEO is significantly affected by the chemical modification of the PI block, probably due to hydrogen bond formation and polar interactions.

All synthesized copolymers were studied regarding their self-assembly behavior in aqueous solutions by dynamic (DLS) and static light scattering (SLS) measurements and fluorescence spectroscopy experiments. In most cases, the copolymers form almost spherical micelles with a HOPI core and PEO corona, with high aggregation numbers and relatively low cmc values.

1 Alexandridis P, Lindman B, Eds Amphiphilic Block Copolymers. Self Assembly and Applications, Elsevier: Amsterdam, 2000. 2 Blanazs A, Armes SP, Ryan AJ Macromol. Rapid Commun. 2009;30 :237. 3 Rapoport N Prog. Polym. Sci. 2007;32: 962. 4 Kaditi E, Pispas S J. Polym. Sci. Part A: Polym. Chem. 2010; 48: 24.


127

PI-42: THERMOSENSITIVE AMPHIPHILIC BRUSH-LIKE BLOCK COPOLYMERS OF PEO AND PPO VIA A COMBINATION OF CONVENTIONAL

AND METAL-FREE ANIONIC POLYMERIZATION JUNPENG ZHAO1,2, GRIGORIS MOUNTRICHAS1, GUANGZHAO ZHANG2, STERGIOS

PISPAS1 1Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, 48 Vassileos

Constantinou Ave., 11635 Athens, Greece - [email protected] 2Hefei National Laboratory for Physical Sciences at Microscale, University of Science and

Technology of China, Hefei 230026, Anhui, China

Abstract

Amphiphilic graft copolymers with poly(ethylene oxide) (PEO) being the hydrophilic side chains, have gained extensive academic interest in terms of synthesis, physical properties and applications.1,2

The quest for new block copolymer architectures containing PEO, that will expand the range of available polymeric materials and will enrich the existing knowledge on structure-properties relationships is on-going.

In this work we present the synthesis of amphiphilic and thermosensitive brush-like copolymers with poly(propylene oxide-b-ethylene oxide) (PPO-b-PEO) side chains and a poly(p-hydroxystyrene) (PHOS) backbone, (PHOS-g-(PPO-b-PEO) brush-like copolymers).3 The copolymers were synthesized by a combination of traditional and metal free anionic polymerization. The PPO-b-PEO side chains (or PEO-b-PPO depending on the mode of side chain connection to the backbone) were synthesized by metal-free anionic ring-opening polymerization of oxirane monomers, using the phosphazene base (t-BuP4) and the phenolic hydroxyl groups (PhOH) in the PHOS backbones, as the complex multifunctional initiating system. Well defined copolymers of low polydispersity and with variable molecular characteristics were obtained. The aggregates formed by these copolymers in aqueous media were also studied by aid of light scattering and fluorescence spectroscopy techniques. For the PHOS-g-(PPO-b-PEO) copolymers in aqueous media, temperature-induced intramolecular chain contraction/association and intermolecular aggregation could both be observed at different stages of the heating process. Solutions of the PHOS-g-(PEO-b-PPO) copolymers became unstable at high temperatures, due to extensive intermolecular association even at low concentrations. The adsorption behaviour of these brush-like block copolymers on surfaces, as well as the structure of the formed layers, in contact with the aqueous copolymer solutions, will be also discussed.

1 H-Q. Xie, D. Xie Prog. Polym. Sci. 1999, 24, 275. 2 a) R. Zhang, A. Seki, T. Ishizone, H. Yokoyama Langmuir 2008, 24, 5527. b) A. Oyane, T. Ishizone, M. Uchida, K. Furukawa, T. Ushida, H. Yokoyama Adv. Mater. 2005, 17, 2329. 3 J. Zhao, G.. Mountrichas, G.. Zhang, S. Pispas Macromolecules 2010, 43, 1771.


128

PI-43: SYNTHESIS AND PROPERTIES OF NOVEL SULFIDE BRIDGED POLYIMIDES BASED ON NONCOPLANAR THIAZOLE CONTAINING DIAMINE

ALI JAVADI1,2, ABBAS SHOCKRAVI1 1Faculty of Chemistry, Tarbiat Moallem University, No. 49, Postal Code 1571914911 Tehran (Iran) –

[email protected] 2Iranian Academic Center for Education, Culture and Research, Tarbiat Moallem Branch, Tehran

(Iran)

Abstract

Aromatic polyimides (PIs) have been widely used in high temperature films, adhesives, molded parts and microelectronic encapsulation, aviation and separation for the past few decades due to their excellent thermal stability, mechanical strength, low dielectric constants, adhesive and mechanical properties, chemical resistance, and dimensional stability. However, the commercial use of these materials is often limited because of their poor solubility, and high softening or melting temperatures. The incorporation of flexible linkages and introduction of noncoplanar groups into the polymer structure are some of the approaches used to make polyimides more tractable and soluble. Furthermore, the formation of noncoplanar unit through the introduction of thiazole rings with rigid and heteroaromatic structure into the polyimide backbones keeps the advantages of the rigid rod-like polyimides with planar structure, such as interlevel dielectrics and packaging applications including low thermal expansion and excellent mechanical strength.1 In addition, the presence of thioether linkages can induce important new properties, such as less water absorption, better fire-retardant properties, and higher refractive indices for the resulting polymers.2 As a continuation of our efforts in preparing easily processable high-performance polymers,3 this study explores the synthesis and basic characterization of a new class of sulfide bridged poly(thiazole imide)s (PTIs) by polycondensation of a thiazole-containing diamine (DA) with various aromatic dianhydrides via one-step process. The resulting polyimides were obtained in high yields and possessed inherent viscosities in the range of 0.91–1.19 dL g–1. All of the polymers were amorphous in nature, showed outstanding solubility and could be easily dissolved in amide-type polar aprotic solvents and even dissolved in less polar solvents. They showed good thermal stability with the glass transition temperatures between 211-245 °C, the 10% weight loss of 485–522 °C in nitrogen and 479–509 °C in air, and the residue at 700 °C of 52–67% in nitrogen. Moreover, these PTIs possessed low refractive indexes (n = 1.73–1.81) and low birefringence due to the thiazole rings and the flexible thioether linkages that interrupt chain packing and increase free volume.

N

S

S

N

S

H2N

NH2

H3C

CH3

Isoquinoline / m-Cresol

OO

O O

O O

Ar

N

S

S

N

S

H3C

CH3

NN

O O

O O

Ar

n

DA PTI-a-d

Ar : O

O

PMDA ODPA BTDA BPDA

a b c d

1 Y. Aihara and P. Cebe, Polym. Eng. Sci., 34 (1994) 1275. 2 C. Berti, A. Celli, E. Marianucci and M. Vannini, Eur. Polym. J., 43 (2007) 2453. 3 A. Shockravi, E. Abouzari-Lotf, A. Javadi and F. Atabaki, Eur. Polym. J., 45 (2009) 1599.


129

PI-44: SULFONATED AROMATIC POLYETHERS CONTAINING PYRIDINE UNITS AS MEMBRANES FOR HIGH TEMPERATURE PEM FUEL CELLS

IOANNIS KALAMARAS1, MARIA K.DALETOU1 JOANNIS K. KALLITSIS1,2,3

and VASILIS G. GREGORIOU1,2

1Foundation for Research and Technology-Hellas, Institute of Chemical Engineering and High Temperature Chemical Processes (FORTH/ICEHT), Patras 26504, Greece.

[email protected] 2Advent Technologies S. A., Scientific Park of Patras, Patras 26504, Greece.

3Department of Chemistry, University of Patras, Patras 26500, Greece.

Abstract

Fuel cells are a more efficient and environmentally friendly technology of power generation than current power sources. Among others, polymer electrolyte membrane fuel cell (PEMFC) is one of the most promising candidates and has been receiving increased attention due to its certain advantages. Applications of PEM fuel cells are seen in vehicular transportation, electric utility and other applications requiring clean, quiet and portable power. Operating above 150ºC has many advantages such as increased reaction rate, flexibility to use not so pure hydrogen as fuel and/or lower loading of the expensive metal (Pt) on the electrode. Research is underway to optimize the performance of the high temperature PEM fuel cells by finding the electrolyte material that combines certain prerequisites. The ideal polymer electrolyte, for this type of cell, should exhibit long term durability, good mechanical properties and high thermal and oxidative stability in order to be applicable in the particular conditions under which the cell operates. Moreover it should be able to be doped with a strong acid like phosphoric acid in order to posses high proton conductivity1,2. In this project we synthesized aromatic copolymers bearing in the main chain basic pyridine groups combined with side chain acidic sulfonate groups, making them capable of absorbing phosphoric acid and water (Figure 1). The membranes are tough flexible and transparent having excellent mechanical properties.

Figure1: Structure of aromatic copolymers A detailed study of the influence of the different functionalities on their thermal properties and the phosphoric acid or water doping ability and subsequently to their ionic conductivity was performed. It was noticed that the presence of the sulfonated groups increases the proton conductivity. Furthermore the copolymers present remarkable oxidave stability compare to Nafion and SPEEK.

Acknowledgement: Financial support of this work from the European Commission (JTI -FCH-JU) through the program DEMMEA FCH-JU 245156 (2010–2012) is greatly acknowledged.

1 J. K. Kallitsis, M. Geormezi, S. G. Neophytides, Polym. Int., 58, 2009, 1226-1233. 2 M.K. Daletou, M. Geormezi, E. K. Pefkianakis, C.Morphopoulou, J. K. Kallitsis, Fuel Cells, 10, 2010, 35-44.


130

PI-45: EFFECT OF THE MOLECULAR STRUCTURE ON THE PROPERTIES OF HIGH TEMPERATURE POLYMER ELECTROLYTE MEMBRANES

CHRISTINE MORFOPOULOU1,2, MARIA GEORMEZI1,3, AIKATERINI K. ANDREOPOULOU1,2, STYLIANOS NEOPHYTIDES,2,3 JOANNIS K. KALLITSIS1,2,3

1Department of Chemistry, University of Patras, GR-26500 Rio-Patras, Greece – christmorf@upatras,gr

2Institute of Chemical Engineering and High Temperature Chemical Processes, ICE/HT-FORTH, Post Office Box 1414, GR-26504 Rio-Patras, Greece

3Advent Technologies SA, Patras Science Park, GR-26504 Rio-Patras, Greece

Abstract

Fuel cells are electrochemical devices with high energy conversion efficiency, minimized pollutant emission and other advanced features. Proton exchange membrane fuel cells (PEMFCs), especially those operating at high temperatures, are the most attractive as far as automobile and stationary applications are concerned. Up to now the most successful examples of fuel cells operating above 140°C utilize phosphoric acid doped polybenzimidazole membranes. Current research interest focuses not only on achieving higher molecular weight polymers with improved solubility and processability, but also through synthesizing polymers with tailored basic sites that could improve the acid–base properties of the membranes. Herein we present our approach to the synthesis of copolymers containing methyl-aromatic substituents and basic main chain groups having high molecular weights, increased solubility and the ability to form complexes with strong protic acids. It was found that not only the basic groups content influences the phosphoric acid doping level but also the introduction of the more bulky methyl-phenyl side moieties strongly differentiate these polymeric series from previously examined ones.1,2 More specifically, it was found that the phosphoric acid doping ability is dramatically influenced by the presence of the polar groups and the detailed copolymer structure, as even small differences on the pyridine content resulted in drastic increase of the phosphoric acid level.

Membranes based on these copolymers, obtained after polymer synthesis optimization, were tested in single cells operating at temperatures 160-180 °C where the influence of the different parameters (e.g membrane structure, doping level, electrode used) on the final single cell performance were studied. Acknowledgement: Financial support of this work from the European Commission (JTI -FCH-JU) through the program IRAFC FCH-JU 245202 (2010–2012) is greatly acknowledged.

1 E. K. Pefkianakis, V. Deimede, M. K. Daletou, N. Gourdoupi, J. K. Kallitsis, Macromol. Rapid Commun. 2005, 26, 1724–1728. 2 M. Geormezi, V. Deimede, N. Gourdoupi, N. Triantafyllopoulos, S. Neophytides, J.K. Kallitsis, Macromolecules, 2008, 41, 9051–9056.


131

0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 1,8 2,0

1

10

100

1000

10000

Cpolymer: 2.5 %(w/v)

P(MMA47-co-SSNa)PSSNA

P(MMA21-co-SSNa)

P(MMA53-co-SSNa)

P(MMA32-co-SSNa)

P(MMA14-co-SSNa)

η (c

p)

r

Fig. 2: Variation of the viscosity with the mixing ratio r of aqueous P(MMAx-co-SSNa)/CTAB solutions .

Fig. 1: Transparent solution (r=0.6), viscous solution (r=1.2) and syneresis (r=1.4) of aqueous P(MMA21-co-SSNa)/CTAB mixtu-res.

PI-46: ASSOCIATION OF CETYL TRIMETYLAMMONIUM BROMIDE WITH POLY(METHYL METHACRYLATE –co-SODIUM STYRENE SULFONATE)

RANDOM COPOLYMERS: FORMATION OF HYBRID WORMLIKE MICELLES AND VISCOELASTIC BEHAVIOR IN AQUEOUS SOLUTION

EVDOKIA K.OIKONOMOU 1,2, GEORGIOS BOKIAS 1, JOANNIS. K KALLITSIS 1,2 1Department of Chemistry, University of Patras, GR-26504 Patras, Greece

E-mail:[email protected] 2Foundation of Research and Technology Hellas, Institute of Chemical Engineering and High

Temperature Chemical Processes (ICE/HT FORTH), P.O. Box 1414, GR- 26504 Patras, Greece

It is well known that when charged surfactants, like cetyltrimethylammonium bromide

(CTAB), are mixed in aqueous solution with oppositely charged polyelectrolytes, like poly(sodium styrene sulfonate) (PSSNa), the so-called ‘polymer-surfactant complexes’ are formed, phase separating from water when the charge stoichiometry is approached. On the other hand, cationic surfactants like CTAB self-assemble in aqueous solutions at elevated concentrations to form long supramolecular structures, called wormlike micelles (WLMs). Moreover, it has been demonstrated1 that CTAB forms hybrid WLMs, when random copolymers P(St-co-SSNa) of styrene (St) with sodium styrene sulfonate (SSNa) are used, instead of the homopolymer PSSNa. This behavior has been attributed to cation-π interactions, involving also the hydrophobic uncharged styrene units.

The aim of the present work was to investigate whether the formation of hybrid WLMs is possibly more general and it is not restricted only to P(St-co-PSSNa) copolymers, or similar copolymers containing phenyl rings in all repeating units. To this end, we synthesized through radical copolymerization a series of copolymers of SSNa with a hydrophobic monomer without any aromatic group like methyl methacrylate, MMA. The MMA content, x, of these P(MMAx-co-SSNa) copolymers ranges from 0 up to more than 50 mol%, i.e. close to the solubility limits of these products in water. The behavior of the copolymers in aqueous solution upon mixing with the cationic surfactant CTAB was systematically investigated as a function of several factors, such as chemical composition of the copolymer, mixing ratio, polymer concentration and ionic strength.

As it is illustrated in Figure 1, the phase separation behavior is mainly controlled by the mixing molar ratio r of CTAB over SSNa units. Thus, the initially transparent low-viscosity solutions turn to highly viscous or viscoelastic solutions as r approaches unity. At higher r values phase separation of compact solids or syneresis may take place in pure water for the copolymers with low MMA content (x<21). However, these phenomena are avoided for higher MMA contents. The rheology of hybrid WLMs formed was systematically investigated through shear and dynamic rheology studies, as a function of polymer concentration, mixing ratio r and ionic strength. Some representative results are shown in figure 2. As seen, for the copolymers with intermediate MMA contents (x=20-40), an abrupt viscosity increase, indicative of the formation of hybrid WLMs, is observed for r>0.8. It should be mentioned that the rich rheological behavior of these hybrid WLMS makes these materials attractive for applications in various fields, for instance in home and personal care products or in fracturing fluids.

1 Nakamura K., Shikata T. Macromolecules 2004, 37, 8381-8388.


132

PI-47: SIDE CHAIN CROSSLINKING OF UNSATURATED AROMATIC POLYETHERS FOR HIGH TEMPERATURE POLYMER ELECTROLYTE

MEMBRANE FUEL CELLS (PEMFCs) KONSTANDINIA D. PAPADIMITRIOU1, ANREA VÖGE2 AND JOANNIS K. KALLITSIS1,2,3 1 Department of Chemistry, University of Patras, 26500 Patras (Greece) - [email protected] 2 Foundation of Research and Technology-Hellas, Institute of Chemical Engineering and High

Temperature Processes (FORTH-ICE/HT), 26504 Patras (Greece) 3 Advent Technologies S.A., Patras Science Park, Stadiou Str., 26504 Patras (Greece)

Abstract

Polymer electrolyte membranes for high-temperature fuel cells (PEMFCs) must show thermal,

mechanical, and oxidative stability under the operational conditions. At the same time the membranes have to enable proton conduction, hence a high acid uptake is required for high ionic conductivities.

Our group reported the synthesis of aromatic polyethers containing polar pyridine units and phosphine oxide or sulfone moieties in the main chain.1 These polymers exhibit excellent film-forming properties, high glass transition temperatures (Tg) above 280°C, high oxidative and thermal stability (up to 400°C). Moreover, they can be doped with phosphoric acid at high doping levels resulting in high ionic conductivities in the range of 10-2 S/cm.1, 2

In this report we explore the possibility to create crosslinked membranes based on aromatic

polyethers containing polar pyridine units. In this respect we try to improve the mechanical properties in terms of glass transition as well as stability of the doped membranes by hindering the rapture of the membrane-electrode assemblies (MEAs) under operating conditions. A promising approach to this direction is the introduction of side crosslinkable groups, (e.g., double or triple bonds, Scheme 1) into aromatic polyethers, followed by crosslinking. Crosslinking of double bonds containing polymers3 with, e.g., bisazides or dibenzoylperoxide, afford an opportunity for higher Tg values and higher thermal stabilities compared to the neat polymers. Also it was observed that thermal crosslinking of ethynyl-terminated aromatic polyethers by thermal curing improve the thermal stability and leads to Tg values up to 258°C.4

The effect of the crosslinking on the thermal properties and the phosphoric acid doping ability of the prepared membranes were studied. Selected crosslinked membranes were tested in single cell operating at high temperatures.

Acknowledgement: Financial support of this work from the European Commission (JTI -FCH-JU) through the program IRAFC FCH-JU 245202 (2010–2012) is greatly acknowledged.

1 J. K. Kallitsis, M. Geormezi, S. G. Neophytides, Polym. Int., 58, 2009, 1226-1233. 2 M.K. Daletou, M. Geormezi, E. K. Pefkianakis, C.Morphopoulou, J. K. Kallitsis, Fuel Cells, 10, 2010, 35-44. 3 S. Feng, Y. Shang, X. Xie, Y. Wang, J. Xu, J. Membr. Sci., 335, 2009, 13-20. 4 M.-H. Jeong, K.-S. Lee, J.-S. Lee, J. Membr. Sci., 337, 2009, 145-152.

OO

Ph

Ph

ON

O SO

OO O S

O

Ox y

SO

OO O S

O

Ox y

Scheme 1. Examples of copolymers containing double and triple bonds.


133

PI-48: QUINOLINE-LABELLED WATER-SOLUBLE COPOLYMERS: STRUCTURE CONTROL OF THE PH- RESPONSIVE OPTICAL PROPERTIES

IN AQUEOUS SOLUTION

IOANNIS THIVAIOS, SOUZANA KOURKOULI, ANDREAS STEFOPOULOS, GEORGIOS BOKIAS, JOANNIS K. KALLITSIS

Department of Chemistry, University of Patras, GR-26504 Patras,[email protected]

Abstract As a result of the protonization-deprotonization equilibrium of the quinoline group, the optical

properties (absorption and, more important, emission of light) of quinoline-containing materials are controlled by the pH of the surrounding environment. In fact, the emitted light of the quinoline group changes from blue to green upon decreasing pH. Thus, the design of water-soluble copolymers containing such groups gives rise to a new family of optically pH-responsive materials.

In the present work, the synthesis and photophysical properties in aqueous solution of a series of quinoline-labelled water-soluble copolymers are presented. These copolymers (Scheme I) have been synthesized through free radical copolymerization of water-insoluble vinylic quinoline monomer with water soluble monomers such as the nonionic N,N-dimethylacrylamide (DMAM), and the anionic sodium 2-acrylamido-methylpropanesulfonate (AMPSA). Two qunoline-containing monomers have been used, namely 2,4- diphenyl- 6- (4-vinylphenyl)qui-noline (SDPQ) and a –CN modified derivative, (SDPQCN). The optical properties of the four copolymers synthesized, P(DMAM-co-SDPQ), P(DMAM-co-SDPQCN), P(AMPSA-co-SDPQ) and P(AMPSA-co-SDPQCN) were explored in aqueous solution as a function of pH. Some characteristic absorption and emission spectra at pH=4 are shown in Figures 1 and 2. The insets in Figures 1 and 2 present the pH-dependence of the absorption at 390 nm (attributed to the protonated form of quinoline) and the emission at 420 nm (attributed to the uncharged form of quinoline), respectively. It is clear that the optical response to pH of these water-soluble copolymers is controlled both by the nature of the water-soluble monomer and the existence of substituents, such as –CN, in the quinoline ring.

250 300 350 400 450 500

0.0

0.2

0.4

0.6

0.8

1.0

1.2 P(DMAM-co-SDPQCN)

P(DMAM-co-SDPQ) P(AMPSA-co-SDPQ)

P(AMPSA-co-SDPQCN)

pH=4

Abs

orba

nce

(a.u

.)

Wavelength (nm)

1 2 3 4 5 6 7 8 9

0.00

0.05

0.10

0.15

0.20

0.25

Abso

rban

ce a

t 390

nm (a

.u.)

pH

Fig 1: Absorption spectra of the quinoline–labeled copolymers at pH=4. Inset : pH-dependence of the absorption at 390nm.

350 400 450 500 550 600 6500

50

100

150

200

250

P(DMAM-co-SDPQ)

P(DMAM-co-SDPQCN)

P(AMPSA-co-SDPQCN)

P(AMPSA-co-SDPQ)

pH=4

PL

Inte

nsity

(a.u

.)

Wavelength (nm)

0 1 2 3 4 5 6 7 80

50

100

150

200

250

300

PL

Inte

nsity

at 4

20nm

(a.u

.)

pH

Fig 2: Photoluminescence spectra of the quinoline-labeled copolymers at pH=4. Inset : pH-dependence of the emission at 420nm.

Scheme I

HC

NCH3H3C

CH2HC CH2C O

N

x1-x

R

HC

NH

CH2HC CH2C O

N

x1-x

R

CCH2

H3C

SO3-Na+

CH3

: R = -H or -CN

PDMAM

PAMPSA


134

PI-49: APPLICATION OF QUINOLINE-LABELLED WATER SOLUBLE POLYMERS FOR THE INVESTIGATION OF THE POLYELECTROLYTE /

SURFACTANT COMPLEXATION IN AQUEOUS SOLUTION

IOANNIS THIVAIOS, GEORGIOS BOKIAS Department of Chemistry, University of Patras, GR-26504 Patras, Greece

Abstract

In contrast to typical hydrophilic nonionic polymers such as poly(N,N-dimethylacrylamide)

(PDMAM), it is well-known that negatively charged polyelectrolytes such as poly(sodium 2-acrylamido-methylpropanesulfonate (PAMPSA) form the so-called polyelectrolyte/surfactant complexes when they are mixed in aqueous solution with oppositely charged surfactants, like N,N,N,N-dodecyltrimethylammonium chloride (DTAC). Thus, hydrophobic mixed polymer/surfactant aggregates are formed at a critical aggregation concentration (CAC) much lower than the critical micelle concentration (CMC) of the pure surfactant, leading to associative phase separation when the net charge of the polyelectrolyte chain is sufficiently decreased due to complexation.

In the present work, our target was to investigate whether it is possible to exploit the pH-sensitive optical properties of quinoline group for the study of polyelectrolyte/surfactant complexation in dilute aqueous solution. For this reason, two quinoline-labelled water-soluble polymers, namely the nonionic (P(DMAM-co-SDPQ)) and the negatively charged (P(AMPSA-co-SDPQ)), were synthesized through free radical polymerization, using the hydrophobic vinylic quinoline derivative 2-4-diphenyl-6-(4-vinylphenyl)quinoline (SDPQ).

The optical properties (absorption and emission spectra) of these quinoline-labelled polymers were monitored upon titration with an aqueous DTAC solution in a wide pH range (pH=2-8). Some representative photoluminescence spectra upon excitation at 350 nm at pH=2 are shown in Figures 1 and 2. At this low pH, SDPQ is protonated and a strong emission at ~500 nm is observed. As expected, emission is practically unaffected when the nonionic P(DMAM-co-SDPQ) copolymer is titrated with DTAC, since no polymer/surfactant complexation can take place. This is also the case when the anionic P(AMPSA-co-SDPQ) copolymer is used, as long as the surfactant concentration is lower than CAC. However, when the DTAC concentration exceeds CAC (yellow curve), the emission at ~500 nm weakens substantially. In addition, a new band at ~420 nm appears, usually observed when SDPQ is under the uncharged basic form. While not yet fully understood, this intriguing behavior is possibly explained by a selective solubilization of the hydrophobic uncharged SDPQ species in the interior of the polyelectrolyte/surfactant hydrophobic aggregates formed above CAC.

400 450 500 550 600 6500

20

40

60

80

100

120

140 0mM DTAC

0,5mM DTAC

Excitation at 350nm

PL

Inte

nsity

(a.u

.)

Wavelength (nm)

Figure 1: Photoluminescence spectra of the P(DMAM-co-SDPQ) copolymer upon titration with DTAC at pH=2

400 450 500 550 6000

20

40

60

80

100

120

140

0,9mM DTAC

0,9mM DTAC

0 mM DTAC

0 mM DTAC

Excitation at 350nm

PL In

tens

ity (a

.u)

Wavelength (nm)

Figure 2: Photoluminescence spectra of the P(AMPSA-co-SDPQ) copolymer upon titration with DTAC at pH=2


135

PI-50: REPEATABLE PHOTOINDUCED SELF-HEALING OF TRITHIOCARBONATE CROSS-LINKED POLYMERS

YOSHIFUMI AMAMOTO1,2, JUN KAMADA1, HIDEYUKI OTSUKA2, ATSUSHI TAKAHARA2, AND KRZYSZTOF MATYJASZEWSKI1*

1Center for Macromolecular Engineering, Department of Chemistry, Carnegie Mellon University 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, USA – [email protected]

2Institute for Materials Chemistry and Engineering, Kyushu University 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan

Abstract

Self-healing of cross-linked polymers with reversible covalent bonds have been studied, because they could indicate both repeatable reactions and robust structures. Previously, we demonstrated self-healing reactions of polymer gels based on reshuffling reactions of trithiocarbonate (TTC) units via chemical stimulation procedures.1 Here, we show that TTC based systems are “photoresponsive” and can indeed undergo repeatable self-healing procedures based on radical reshuffling of TTC units, as shown in Figure 1. A polymer cross-linked with TTC units was synthesized by a RAFT copolymerization of n-butyl acrylate (BA) and a TTC cross-linker using 2,2’-azobis(isobutyronitrile) (AIBN) ([BA]/[TTC cross-linker]/[AIBN] = 19/1/0.7) in anisole at 60 ºC, and was obtained with a high conversion after 24 h (99+% (NMR)). The self-healing reactions were carried out by exposing to UV light a sample of TTC cross-linked polymers that had been cut into three pieces and placed under mild pressure by a 4 g weight, in acetonitrile under nitrogen atmosphere. As shown in Figure 2a, after UV irradiation for 4 h, the three pieces were fused into a single sample. This result indicated that the samples had undergone a photo-stimulated macroscopic self-healing fusion reaction. Furthermore, a 2nd self-healing reaction was carried out under the same conditions using the once healed cross-linked polymers. As in the 1st reaction, the three pieces of the cross-linked polymers combined into one piece (Figure 2b). Figure 2c shows a photograph of a swollen cross-linked polymer dipped in anisole for 6 h, after the 2nd healing cycle. This suggests that the final sample formed a clear and transparent single piece, indicating that the resulting gel was not only physically entangled, but also chemically fused. The TTC cross-linked polymer has also showed self-healing in bulk states, macroscopic fusion of completely separated parts, and the controls of swelling degrees by solvents in UV irradiations.

1R. Nicolay, J. Kamada, A. Van Wassen, K. Matyjaszewski, Macromolecules 2010, 43, 4355–4361.

Figure 2. Photographs of cross-linked polymers in repetitive self-healing reactions under UV irradiation in acetonitrile before and after (a) 1st reaction for 4 h, (b) 2nd reaction for 12 h, and (c) after swelling test in anisole for 6 h.

Figure 1. Model self-healing reactions by UV irradiation and radical reshuffling reaction of trithiocarbonate units.

hν

: Butyl Acrylate : TTC Units

S S

SR R R R

hν

S S

SR R R R

S S

SR R R R

R = H, CH3

S S

SR R

S S

S R RRR

RR

S S

S

Reshuffling Reaction

S S

SR R R R

(2)

(3)

(4) (2)

(3)

(4)

(1)(1)


136

PI-51: FUNCTIONAL HYBRID MATERIALS FOR TWO PHOTON FABRICATION OF SEMICONDUCTING 3D STRUCTURES

KAMBOURAKI ELMINA,1,2 FARSARI MARIA,1 VAMVAKAKI MARIA,1,2 FOTAKIS COSTAS1 1Institute of Electronic Structure and Laser, Foundation for Research and Technology – Hellas,

P. O. Box 1527 Vasilika Vouton, 711 10 Heraclion, Crete (Greece) – [email protected] 2Department of Materials Science and Technology, University of Crete, P.O. 2208 Vasilika Vouton,

710 03 Heraclion, Crete (Greece)

Abstract

The sol-gel process is a simple cost effective and efficient method used for the preparation of inorganic networks.1 This versatile technique has been exploited for the incorporation of inorganic networks into polymer matrices, using as monomers molecules that carry an inorganic part which serves as the precursor to the inorganic network and a polymerizable organic group which acts as the precursor to the organic polymer. In the present work, we have synthesized novel hybrid organic-inorganic microstructures for photonic and semiconducting applications by combining the sol-gel process with the two-photon polymerization (2PP) technique. 2 We first prepared a composite material based on a polymerizable silicon precursor, and a cadmium containing organic salt. Films of this material were prepared onto glass slides by spin coating or drop casting. Next, the inorganic siloxane network was formed by the sol-gel process, whereas, the photosensitivity that this material demonstrates, allowed its 3D structuring using the 2PP technique. 3D microstructures with spatial resolution below 100 nm which exhibit minimal shrinkage were fabricated by this method (Figure 1).

Figure 1. SEM images of woodpile structures fabricated from the cadmium containing composite material

Furthermore, the microstructures were reacted with Na2S which led to the synthesis of cadmium sulphide (CdS) quantum dots within the volume of the 3D structures. The X-Ray diffraction pattern of a CdS containing film showed three broad peaks attributed to the crystalline cubic structure of the nanoparticles.3 The UV-VIS absorption spectra showed a series of overlapping peaks, which are characteristic of polydisperse CdS quantum dots formed within the material. Fluorescence spectroscopy was used to measure the emission attributed to the CdS nanoparticles which was found in the visible region of the electromagnetic spectrum.

1 Schmidt, H. J. Sol-Gel Sci. Technol. 1994, 1, 217-231 2 Ovsianikov, A.; Gaidukeviciute, A.; Chickov, B. N.; Oubaha, M.; MacGraith, B. D.; Sakellari, I.; Giakoumaki, A.; Gray, D.; Vamvakaki, M.; Farsari, M.; Fotakis, C. Laser Chem. 2008, Article ID 493059. 3 Martínez-Castañón, G. A.; Sánchez-Loredo, M. G.; Martínez-Mendoza, J. R.; Facundo, R. Azojomo-Journal of marerials online 2005, 1, DOI: 10.2240/azojomo0170.


137

PI-52: PHOTODEGRADABLE POLYMERS AS SUBSTRATES FOR POST-CULTURE CELL PATTERNING

GEORGE PASPARAKIS,1 THEODORE MANOURAS,2 ALEXANDROS SELIMIS,1 STELIOS PSYCHARAKIS,1 ANTHI RANELLA,1 PANAGIOTIS ARGITIS2 AND MARIA VAMVAKAKI1,3

1Institute of Electronic Structure and Laser – Foundation for Research and Technology Hellas, 711 10 Heraklion, Greece - [email protected]

2Institute of Microelectronics, NCSR Demokritos, 153 10 Aghia Paraskevi, Attiki Greece 3Department of Materials Science and Technology, University of Crete, 710 03 Heraklion, Crete,

Greece

Abstract

Degradable polymers are constantly developed and find numerous uses in the biotechnological arena, for example, in the fields of drug delivery and tissue engineering as carriers for sustained or stimulus-mediated drug release and as scaffolds for tissue culture. Although there are many examples of generally regarded as safe (GRAS) materials that exhibit degradation upon (bio-)chemical stimuli1 (i.e. pH, enzymes, etc.), photodegradable polymers, addressable in the biomedical context remain limited, mainly due to very slow degradation rates, and high energy required for complete photodegradation.

In this study, we explore the synthesis and photodegradation properties of novel ketal-based polymers for post-culture cell patterning. Model polymers with ketal segments on their main chain were synthesized by standard condensation polymerization procedures. Thin polymer films (150 μm thickness) were fabricated by spin coating polymer solutions on quartz substrates in order to examine the photodegradation profiles by laser induced fluorescence (LIF) spectroscopy. A nanosecond (ns) excimer laser source at 193 nm was used for the photolysis studies with a fluence of 7 mJ/cm2 per pulse. A rapid reduction of film thickness was evidenced by LIF spectra due to rapid fluorescence decrease as photoablation process progressed. The polymers were found to exhibit complete photodegradation2 at remarkably low energies ca. <60 mJ/cm2.

We then sought to use the polymer films as cell-culture photodegradable substrates to mediate laser controlled cell detachment and harvesting, and to construct 2D cell patterns on the ablated substrates. 3T3 fibroblasts were cultured on the polyketal films followed by laser ablation of selected areas by application of a mask. Cells were detached from the irradiated areas due to polymer photodegradation. Ablated cells were harvested alive whereas non-irradiated areas formed 2D patterns with cells attached on them. It should be stressed that cells remained viable after irradiation due to the very low fluencies required for complete substrate ablation and the fact that the polymers exhibit strong absorbance at 193 nm and act as a shielding layer protecting the cells from direct laser exposure. In addition, the photodegradation products were found to be of low toxicity and hence did not affect the viability of the cells after laser detachment. Finally, the short pulse duration used further eliminates photothermal effects to occur and heat transfer phenomena are limited.

In conclusion, polyketals constitute an excellent class of photodegradable GRAS materials for biomedical applications in the UV regime with remarkably low degradation energies. Fine tuning of the photochemical degradation process is currently in progress as well as the investigation of the photochemical degradability of polyketals in aqueous solutions for phototriggered drug delivery applications.

1 L.S. Nair, C.T. Laurencin, Prog. Polym. Sci. 32, 762-798 (2007). 2 P. Wang, H. Hu, Y. Wang, Org. Lett. 9, 2831-2833 (2007).


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PI-53: SYNTHESIS AND CHARACTERIZATIONOF RESPONSIVE NANOPARTICLES FOR HOMOGENEOUS CATALYSIS

GEORGE PASPARAKIS1, KONSTANTINOS STOIKOS2, MARIA VAMVAKAKI1,2

1Institute of Electronic Structure and Laser – Foundation for Research and Technology Hellas, 711 10 Heraklion, Greece - [email protected]

2Department of Materials Science and Technology, University of Crete, 710 03 Heraklion, Crete, Greece

Abstract

Homogeneous catalysis is widely used by the industry for the production of a plethora of chemical compounds used in everyday products such as cosmetics, food additives, paints etc. A significant drawback of currently used continuous type reactors is that small amounts of, often precious, catalysts are lost during the reaction cycles, resulting in contamination of the final products. In order to address this problem, we envisaged that catalysts could be immobilized on the surface of ‘smart’ particles as a means to recover the catalysts by application of physicochemical stimuli that the particles could ‘feel’ at the end of the reaction cycle. We have successfully synthesized stimuli responsive microgel nanoparticles of varying chemical functionalities and characterized them in solution by DLS, SEM and FT-IR. Precipitation polymerization1 was evaluated as a highly robust and versatile method to produce nearly monodisperse nanoparticles. The particles exhibited temperature responsive properties derived from the selection of suitable monomers (i.e. NIPAM, DMAEMA etc.), which were also combined with hydrophilic functional monomers (i.e. –OH, -COOH, -NH2) for further catalyst immobilization. The nanoparticles could be readily dispersed in aqueous media as well as in many organic solvents (i.e. MeOH, EtOH, THF, DMF, acetone) and were stable for months without any observable disintegration. The nanoparticles were found to form colloidal crystals at high concentrations in aqueous dispersions (>60%), indicative of their uniform size (figure 1a). Particle size uniformity was confirmed by SEM which revealed consistent diameters below 300 nm (figure 1b).

A b c Figure 1. a. Characteristic iridescence of colloidal crystal formed by uniform microgel particles. b. SEM image of a nearly monodisperse core-shell particle population and c. Reversible dispersion-aggregation transition of T-responsive particles in water below and above LCST. Preliminary experiments showed that the particles formed large aggregates above their LCST and could be redispersed back to their initial state by a temperature decrease (figure 1c), which demonstrate their potential of being used as polymer supports for catalytic cycles in continuous type reactors where catalyst recovery is of paramount importance. We are currently performing experiments with fully functionalized particles with catalytic moieties to demonstrate the concept of catalyst recovery by ‘smart’ nanoparticles in laboratory-scale prototype reactors. 1 Jian Qiu, Bernadette Charleux, Krzysztof Matyjaszewski, Prog. Polym. Sci. 26, 2083-2134 (2001).


139

PI-54: BULK HOMOPOLYMERIZATION OF 2-(DIMETHYLAMINO)ETHYL METHACRYLATE VIA ATOM TRANSFER RADICAL POLYMERIZATION

DAFNI MOATSOU1,2, DEMETRA S. ACHILLEOS1,2, MARIA VAMVAKAKI1,2 1Department of Materials Science and Technology, University of Crete, 710 03

Heraklion, Crete, Greece - [email protected] 2Institute of Electronic Structure and Laser, Foundation for Research and Technology – Hellas, 711 10

Heraklion, Crete, Greece

Abstract

Poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) is a pH- and temperature-responsive polymer which has attracted considerable attention lately because it is an excellent candidate for various applications including gene1 and drug delivery,2 bioseparation and water purification. The synthesis of highly functional PDMAEMA-based materials with controlled molecular characteristics, that is controlled molecular weight (MW) and narrow molecular weight distribution (MWD), can be achieved via a “controlled/living” radical polymerization technique such as the atom transfer radical polymerization (ATRP). The controlled synthesis of PDMAEMA homopolymers by ATRP has been extensively investigated during the last decade.3 Most of the studies focused on the synthesis of low molecular weight PDMAEMA homopolymers (~20,000 g/mol) to achieve “living” conditions. Only, Mao et al. reported the synthesis of ultra-high molecular weight PDMAEMA via ATRP in aqueous media.4

In the present work, the bulk homopolymerization of DMAEMA using Cu(I) as the catalyst and 1,1,4,7,10,10 hexamethyltriethylenetetramine (HMTETA) as the ligand, is investigated. The use of copper (I) bromide (Cu(I)Br) vs copper (I) chloride (Cu(I)Cl) as the metal salt is compared by following the kinetics of the ATRP polymerizations in bulk to prepare high molecular weight PDMAEMA homopolymers. The monomer conversion was followed by proton nuclear magnetic resonance (1H NMR), while the MWs and the MWDs of the polymers were determined by gel permeation chromatography (GPC) (Figure 1). The reaction rate was much slower for Cu(I)Cl compared to that for Cu(I)Br resulting in long reaction times. Although high MW PDMAEMA homopolymers of ~100 000 g/mol were obtained in both cases, the polymerization retained its “controlled/living” character only when Cu(I)Cl was used as the metal salt. This was accompanied by an increase of the MW and an exponential decay of the polydispersity index with monomer conversion (Figure 1), as well as the re-initiation of the polymerization from the active polymer chain-ends upon the addition of new monomer.

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conversion. 1 Jiang, X.; Lok, M. C.; Hennink, W. E. Bioconjugate Chem. 2007, 18, 2077-2084. 2 You, J.-O.; Auguste, D. T. Biomaterials 2008, 29, 1950-1957. 3 (a) Zhang, X.; Xia, J.; Matyjaszewski, K. Macromolecules 1998, 31, 5167-5169, (b) Shen, Y.; Zhu, S.; Zeng, F.; Pelton, R. H. Macromol. Chem. Phys. 2000, 201, 1169-1175, (c) Zeng, F.; Shen, Y.; Zhu, S.; Pelton, R. J. Polym. Sci., Part A: Polym. Chem. 2000, 38, 3821-3827, (d) Pantoustier, N.; Moins, S.; Wautier, M.; Degee, P.; Dubois, P. Chem. Commun. 2003, 340-341. 4 Mao, B. W.; Gan, L. H.; Gan, Y. Y. Polymer 2006, 47, 3017-3020.


140

PI-55: MULTIRESPONSIVE SPIROPYRAN-BASED COPOLYMERS SYNTHESIZED BY ATOM TRANSFER RADICAL POLYMERIZATION

DEMETRA S. ACHILLEOS1,2 AND MARIA VAMVAKAKI1,2 1Institute of Electronic Structure and Laser, Foundation for Research and Technology - Hellas,

P.O. Box 1527, 711 10 Heraklion, Crete, Greece - [email protected] 2Department of Materials Science and Technology, University of Crete, P.O. Box 2208, 710 03

Heraklion, Crete, Greece

Abstract Photochromic compounds, which can be interconverted to two thermodynamically stable states of

different color by absorbing electromagnetic radiation have attracted considerable attention lately.1 One of the most extensively studied families of photochromic compounds are spiropyrans (SPs) whose photochromism depends on the polarity of the surrounding medium (solvent or polymer matrix),2 the solution pH3 and the presence of ions.4

Multiresponsive spiropyran-based random copolymers were synthesized by atom transfer radical polymerization (Scheme 1).5 The polymers were prepared by the copolymerization of 2-(dimethylamino)ethyl methacrylate (DMAEMA) with the photochromic monomer 1',3',3'-trimethyl-6-methacryloyloxy-spiro(2H-1-benzopyran-2,2'-indoline) (SP). The solvatochromic, pH, temperature and light responsive behavior of the PDMAEMA-co-PSP polymers in solution was monitored by UV/vis spectroscopy. The copolymers exhibited “reverse photochromism” and stabilized the planar zwitterionic form of the chromophore, leading to “negative solvatochromism” upon increasing the polarity of the solvent, in contrast to a poly(methyl methacrylate)-co-PSP analogue which stabilized a nonpolar photoisomer and exhibited negligible sensitivity to the polarity of the surrounding medium, before irradiation. Moreover, the PDMAEMA-co-PSP copolymers exhibited a reversible pH-responsive character in aqueous media; the addition of a strong acid induced the SP-to-merocyanine (MC) isomerization and the formation of [MC-OH]+ and [SP-NH]+ species, whereas the initial SP moieties were recovered in alkaline media. The chromophore content and the photoinduced MC-to-SP isomerization affected the transition temperature of the PDMAEMA-co-PSP polymers. The lower critical solution temperature (LCST) of the copolymers increased with their content in hydrophilic MC moieties, while the MC-to-SP photoinduced isomerization decreased significantly the LCST due to the hydrophobic character of the SP units. Finally, the copolymers exhibited a first-order photo-induced bleaching of the chromophore units in water and acetonitrile, with a slower decoloration rate in the aqueous medium due to the effective stabilization of the bipolar MC form in the polar environment.

Scheme 1. Responsive behavior of the PDMAEMA-co-PSP copolymers to the solvent polarity, light, the solution pH and temperature.

1 Minkin, V. Chem. Rev. 2004, 104, 2751-2776. 2 Wojtyk, J. T. C.; Wasey, A.; Kazmaier, P. M.; Hoz, S.; Buncel, E. J. Phys. Chem. A 2000, 104, 9046-9055. 3 Raymo, F. M.; Giordani, S. J. Am. Chem. Soc. 2001, 123, 4651-4652. 4 Shiraishi, Y.; Adachi, K.; Itoh, M.; Hirai, T. Org. Lett. 2009, 11, 3482-3485. 5 Achilleos, D. S.; Vamvakaki, M. Macromolecules 2010, Articles ASAP.


141

PI-56: POLYMER PORPHYRIN NANOASSEMPLIES WITH INCORPORATED GOLD NANOPARTICLES

MARIA KALIVA,1,2 GALATEIA E. ZERVAKI3, ATHANASIOS COUTSOLELOS3, MARIA VAMVAKAKI1,2

1Institute of Electronic Structure and Laser, Foundation for Research and Technology, Voutes, 711 10, Heraklion, Greece – [email protected]

2Department of Materials Science & Technology, University of Crete, Voutes, 710 03, Heraklion, Greece

3Department of Chemistry, University of Crete, Voutes, 710 03 Heraklion, Greece Abstract

Porphyrins and metalloporphyrins have received great attention recently, due their interesting photophysical, photochemical and electrochemical properties.1 On the other hand, metal nanoparticles have been also shown to exhibit interesting size dependent electronic, optical and other properties.2 Multicomponent systems containing porphyrins and gold nanoparticles yield photoresponsive organic-inorganic nanohybrid materials with novel electrical, optical and photochemical properties.3 In the present work amphiphilic block copolymers of poly[2-(diethylamino)ethyl methacrylate]-b-poly((oligoethyleneglycol)monomethylether methacrylate) (PDEAEMA-b-POEGMA) were synthesized from a porphyrin difunctional initiator by the ‘grafting from’ technique using a controlled radical polymerization method, atom transfer radical polymerization (Figure 1). The successful synthesis of the terpolymers was verified by nuclear magnetic resonance spectroscopy and gel permeation chromatography. The amphiphilic polymer-porphyrin conjugates self-assemble into spherical micelles in aqueous solution with the porphyrin and PDEAEMA blocks located in the core of the micelle and the POEGMA blocks forming the micelle corona. Next, the micellar core was decorated with gold nanoparticles by incorporation of a metal salt followed by metal reduction (Figure 2). The micellar structures and the gold nanoparticles decorated nanohybrids were characterized by dynamic light scattering and transmission electron microscopy. The electronic properties of the nanohybrids were investigated by fluorescence spectroscopy and showed a quenching of the intensity and shift in the position of the porphyrin bands in the presence of the gold nanoparticles.

Initiator functionalized porphyrinPorphyrin molecule

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AuCl4 NaBH4

Figure 1: Schematic representation of the synthetic procedure followed for the preparation of the amphiphilic polymer-porphyrin conjugates.

Figure 2: (a) Self assembly of the polymer-porphyrin conjugates and (b) Micelles decorated with gold nanoparticles.

1 Z. Wenqi, Y. Lianxiang, W. Xingqiao, Dyes and Pigments 2008, 77, 153-157. 2 V. Myroshynychenko, J. R. Fernandez, I. P. Santos, A. M. Funston, C. Novo, P. Mulvaney, L. M. Marzan, F. J. C. Abajo, Chem. Soc. Rev. 2008, 37, 1792-1805. 3 (a) K. G. Thomas, P. V. Kamat, Acc. Chem. Res. 2003, 36, 888-898. (b) B. I. Ipe, K. G. Thomas, J. Phys. Chem. B 2002, 106, 18-21.

(a)

(b)


142

PI-57: PLASMA NANOTEXTURED AMPHIPHOBIC POLYMER SURFACES

ARUN KUMAR GNANAPPA, KOSMAS ELLINAS, ANGELIKI TSEREPI, EVANGELOS GOGOLIDES

Institute of Microelectronics, National Center for Scientific Research ‘Demokritos’,

Terma Patriahou Gregoriou St. Aghia Paraskevi, 15310 Greece

e-mail: [email protected]

Keywords: superhydrophobic, oleophobic, superoleophobic, contact angle, roughness, plasma etching, nanotexture Random roughness (which we term nanotexture) generated on a polymer surface combined with appropriate surface chemistry may lead to simultaneously superhydrophobic and superoleophobic surfaces. Such surfaces repel both water and oils, a desired combination termed super amphiphobicity. These surfaces are significant for applications such as self-cleaning, drag reduction in microfluidic devices, water / oil repellent fabrics and biology1,2,3,4. Here we demonstrate a simple method for enhancing the water and oil repellence of polymethylmethacrylate (PMMA) using plasma etching and roughening followed by fluorocarbon plasma deposition. The mechanical stability of roughness plays a critical role in maintaining superhydrophobicity for long time and repeated water exposures. This paper discusses the robustness of these surfaces towards immersion in water before and after fluorocarbon coating. In our previous work, the plasma processing conditions were optimized for making superhydrophobic surfaces5. Under optimum conditions, PMMA treated with oxygen plasma to generate roughness, followed by fluorocarbon plasma deposition to alter the surface chemistry leads to creation of superhydrophobic/superoleophobic surfaces. With increasing etching time, pillar-like roughness of increasing height and diameter has been observed6 (see Fig. 1). In this work stability of roughened surface under immersion in water has been studied with SEM at the micro and nanoscale. For long etch time, the PMMA surface becomes very rough with a fibrous surface superimposed on the micropillar-like structure (see Fig 1). These surfaces are found not stable after immersion in water (see Fig. 2) and need to be wetted before their hydrophobization in fluorocarbon plasma. This treatment is shown to be appropriate for rendering a rough surface stable upon immersion in water and vacuum drying. We attribute the observed coalescence of the fibrous structures to the capillary forces acting during the evaporation of water between the rough structures7,8. structures7,8. The stabilized nanotexture on PMMA generated by oxygen plasma, wetting, and drying is then treated with fluorocarbon plasma to create a stable amphiphobic surface. These surfaces are highly superhydrophobic with water contact angle above 1500 and contact angle hysteresis <50 (see Fig 3). Contact angles for these surfaces are improved from oleophobic (CA for water 110-1400) for low etch times to superoleophobic (>1400 and small hysteresis) for higher etch times. The soya oil, the surfaces show oleophobic behavior (but larger hysteresis). The low surface tension liquid hexadecane still 1 B. Leng, Z. Shao, G. de With, W. Mi. Langmuir, 2009, 25 (4), pp 2456–2460 2 McHale G, Shirtcliffe N. J, Newton M. I. Analyst 2004, 129 (4), 284–287. 3 Li H, Wang. X, Song Y, Liu Y, Li Q, Jiang L, Shu D., Angew. Chem., Int. Ed 2001, 40 (9), 1743–1745. 4 Feng, X. J.; Jiang, L. Adv. Mater. 2006, 18 (23), 3063–3078. 5 N. Vourdas, A. Tserepi, E. Gogolides. Nanotechnology 2007, 18, 125304 6 K. Tsougeni, N. Vourdas, A. Tserepi, and E. Gogolides, Langmuir 2009, 25(19), 11748–11759 7 D. Chandra, S. Yang. Langmuir 2009, 25(18), 10430–10434 8 Y. Zhang, Chi-Wei Lo, J. A. Taylor, S. Yang. Langmuir 2006, 22, 8595-8601


143

shows hydrophilic behaviour with contact angle ~700 (see Fig 3). Our current work focuses on improving the contact angle of low surface tension liquids with simple plasma treatment. Finally the hydrolytic stability of these fluorocarbon coated superhydrophobic surfaces is studied by weathering the surfaces in water over a period of time and monitoring its contact angle. The hydrolytic stability of these surfaces is very important due to its long term exposure to water in most of its applications. After prolonged immersion (for 1 month) in water samples etched for less time showed loss of superhydrophobicity (contact angle decreases from 155 to 1350). The longer etched samples showed better stability. 10 mins etched sample showed only a contact angle decreases from 160 to 1450 and are still marginally superhydrophobic.

Figure 1: 10mins oxygen plasma etch PMMA

Figure 2: 10mins oxygen plasma etched PMMA, after wetting and vacuum drying. coalescence of fibrous structures occurs leaving behind micropillars

Figure 3: Static contact angle for various liquids versus etching time of PMMA. Data are taken after wetting-drying of fibrous structures to cause coalescence, and coating with fluorocarbon plasma- deposited film. Water and diiodomethane roll on the surface, while other oils stick.


144

PI-58: SYNTHESIS AND STUDY OF PROPERTIES OF DENTAL RESIN COMPOSITES WITH DIFFERENT NANOSILICA PARTICLES SIZE

MARIA KARABELA, IRINI SIDERIDOU

Laboratory of Organic Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki, GR-54124 Thessaloniki (Greece) - [email protected]

Abstract

Aesthetic tooth-shaded dental restorations are well-accepted and becoming more and more popular over metallic dental amalgams. Posterior restorations require composites that show higher mechanical properties, while anterior restorations need composites that have superior aesthetics. The resin composite that meets all the requirements of both posterior and anterior restorations has not emerged yet. So, the great interest in resin composite research is nanotechnology. The objective of this study was the synthesis of light-cured resin nanocomposites using nanosilica particles with different particles size and the study of some physical-mechanical properties of the composites. These nanocomposites consisted of a Bis-GMA/TEGDMA (50/50wt/wt) matrix and various types silica nanoparticles (Aerosil) with average particle size of 40, 20, 16, 14, and 7nm, used as filler were silanized with the silane 3-methacryloxypropyl-trimethoxysilane (MPS). The total amount of silane used was kept constant at 10 wt-% relative to the filler weight to ensure the complete silanization of nanoparticles. The silanizated silica nanoparticles were identified by FT-IR spectroscopy and thermogravimetric analysis (TGA). Then the silanized nanoparticles (55 wt-%) were mixed with a photoactivated matrix. Degree of conversion of composites was determined by FT-IR analysis. The static flexural strength and flexural modulus were measured using a three-point bending set up, while the dynamic thermomechanical properties were determined by Dynamic Mechanical Analyzer (DMA). Sorption, solubility and volumetric changes were determined after storage of composites in water or ethanol/water solution 75 vol-% for 30 days. TGA of composites was performed in nitrogen atmosphere from 30 to 700 oC.

As average silica particle size decreases, the percentage amount of MPS attached on the silica surface increases. However, the number of MPS molecules attached on the silica surface area 1 nm2 is independent of filler particle size. As the average filler particles size decreases a progressive increase in degree of conversion of composites and an increase in the amount of sorbed water is observed, while no change on mechanical properties is observed. Finally, the small particle size of silica, modified with sufficient amount of coupling agent, ensure better interfacial adhesion between filler and matrix and contribute to uniform dispersion of particles in polymeric network.

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1 Irini D. Sideridou, Maria M. Karabela : Dental Materials 25 (2008) 1315 – 1324. 2 Kristen S. Wilson, Kai Zhang, Joseph M. Antonussi : Biomaterials, 26 (2005) 5095-5103.


145

PI-59: SORPTION OF FOOD-SIMULATING SOLUTIONS BY DENTAL DIMETHACRYLATE RESINS

IRINI SIDERIDOU, MARIA KARABELA

Laboratory of Organic Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki, GR-54124 Thessaloniki (Greece)- [email protected]

Abstract

Dental resins in the oral environment may absorb water and chemicals, such as those found in saliva or food (acids, bases, salts, alcohols etc) and may release components to their surroundings. The process of sorption and desorption of a liquid may produce deleterious effect on the structure and function of the resin. These effects may include volumetric changes, such as plasticization, softening and chemical changes such as oxidation and hydrolysis1. Thus, long-term survival of dental resins under oral conditions is obviously of great concern.

This work is concerned with the study of the sorption and desorption process of water, ethanol, ethanol/water solution 50 vol-% or ethanol/water solution 75 vol-% by the dental resins prepared by light curing of the dimethacrylate monomers Bis-GMA, Bis-EMA, UDMA, TEGDMA or D3MA. The resin specimens (15mm diameter x 1mm height) were immersed in liquids 37±1oC for 30 days and liquids sorption/desorption were examined in both equilibrium and dynamic conditions in a sorption–desorption cycle. The sorbed or desorbed liquid at equilibrium, diffusion coefficients, solubility and volume increase after sorption were calculated.

It was observed that the chemical structure of the monomers used for the preparation of the resins directly affects the amount of liquid sorbed or desorbed, as well as sorption kinetics, while desorption rate was nearly unaffected. An interesting finding concerning the rate of ethanol/water sorption was that all resins followed Fickian diffusion kinetics during almost the whole sorption curve.

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1 Ferracane JL. Dental Materials 22 (2006), 211. 2 Karabela MM, Sideridou ID. Dental Materials 24 (2008) 1631. 3 Kao EC. Dental Materials 5 (1989), 201.


146

PI-60: EFFECT OF THE SODIUM PHOSPHATE DIBASIC CONCENTRATION ON THE SWELLING PROPERTIES OF CHITOSAN HYDROGELS

AGUSTÍN MARTÍNEZ-RUVALCABA1, JUAN C. SÁNCHEZ-DÍAZ1, LUIS E. CRUZ-BARBA1, ALEJANDRO GONZÁLEZ-ÁLVAREZ1, FAUSTO BECERRA-BRACAMONTES2

1Department of Chemical Engineering, University of Guadalajara, Blvd. García Barragan #1421, 44430 Guadalajara (Mexico) – [email protected]

2Department of Chemistry, University of Guadalajara, Blvd. García Barragan #1421, 44430 Guadalajara (Mexico)

Abstract

In this work were prepared chitosan hydrogels by ionotropic gelation technique with sodium phosphate dibasic (SDP) in an aqueous acetic acid solution 2% v/v. The results obtained shows that the ionic interaction of the NH+

3 groups linked to the chitosan chain with the SDP anionic groups is depending of the pH of the swelling media (3, 5, 7, and 11) and the percentage of solids in the hydrogels (2, 3, and 4% w/w). In the acid swelling medium the swelling capacity of the hydrogels was higher respect to the capacities obtained in basic and neutral media; moreover with a percentage of solid of 2% w/w the swelling capacities were higher. An overshooting effect in the hydrogels was observed, followed by a lost in the volume of the hydrogels until the swelling equilibrium is attained. The percentage of swelling was higher when decreased SDP molar ration of the hydrogels. Hydrogels of chitosan/SDP are sensitivity to pH of the swelling; in acidic medium the rate of swelling of hydrogels was high because of the degree of protonation of the ammonium groups in the chitosan and crosslinking density was low. Whereas in basic medium the rate of swelling was low due to the degree of deprotonation of ammonium groups of chitosan and crosslinking density was high by hydrogen bonds. An overshooting effect was observed in the hydrogels swollen in basic and neutral medium, this suggest an increase in crosslinking density due to hydrogen bonds in the anions of SDP, while in acidic medium the hydrogel collapsed.

Swelling ratio for the chitosan/SPD hydrogels at different percentage of solids

for a swelling medium of pH = 7.0


147

PI-61: POLYMER NANOROD ARRAYS FOR OPTICAL WAVEGUIDE-BASED BIOSENSING

ANTONIS GITSAS1*, BASIT YAMEEN2, THOMAS LAZZARA3, MARTIN STEINHART4, HATICE DURAN2, WOLFGANG KNOLL1

1Nano Systems, Austrian Institute of Technology, Donau-City-Strasse 1, 1220 Vienna, Austria – *[email protected]

2Max Planck Institute for Polymer Research, 55128 Mainz, Germany 3Institute for Organic and Biomolecular Chemistry, Universität Göttingen, 37077 Göttingen, Germany

4Institut for Chemistry, University of Osnabrück, 49069 Osnabrück, Germany

Abstract

We demonstrate the optical waveguiding capability of polycyanurate thermoset nanorod (PCN) arrays for high-sensitivity biosensing using optical waveguide spectroscopy (OWS). The nanorods, formed by thermal polymerization of a cyanate ester monomer1 in self-ordered nanoporous alumina templates,2,3 were 60 nm in diameter and 650 nm in length. Subtle refractive index changes of of the medium surrounding the nanorods could be detected by monitoring the angular shifts of waveguiding modes. This study lead to a sensing figure of merit (FOM) of 196 reciprocal refractive index units, which is higher than that for other sensors based on angular modulation, while providing further flexibility for surface functionalization. The chemical affinity of the PCNs sensor was tested by means of a biological model analyte (taurine) binding to the nanorod surface by reaction with residual cyanate groups. Thus, modified PCNs bearing sulfonic acid groups at their surfaces were obtained. PCN arrays may represent a versatile platform for the design of biosensors.

Figure 1. PCN array integrated in an OWS setup. The side view SEM image shows the nanorods situated onto the Au-coated surface of an LaSFN9 glass substrate. OWS scans of the PCN nanorods in different environments (red circles: Milli-Q water; blue squares: isopropanol), demonstrate waveguiding ability and sensitivity to refractive index changes.

What makes this hybrid biosensor platform attractive is that the nanorod array serves both as waveguiding layer and amplifies the number of functional sites available for surface specific processes. This work4 extends the waveguiding ability of nanoporous systems and, additionally, the surface features of the nanorods result in larger molecule binding capability. The nanorod arrays can therefore also be considered for the use as scaffold for optical biosensors with molecularly imprinted polymers (MIPs), with the recognition sites located in the nanorods body.

1 Yameen, B.; Duran, H.; Best, A.; Jonas, U.; Steinhart, M.; Knoll, W. Macromol. Chem. Phys. 2008, 209, 1673. 2 Masuda, H.; Fukuda, K. Science 1995, 268, 1466. 3 Duran, H.; Gitsas, A.; Floudas, G.; Mondeshki, M.; Steinhart, M.; Knoll, W. Macromolecules 2009, 42, 2881. 4 Gitsas, A.; Yameen, B.; Lazzara, T. D.; Steinhart, M.; Duran, H.; Knoll, W. Nano Letters 2010, 10, 2173.


148

PI-62: CRYSTALLIZATION KINETICS OF POLY(E-CAPROLATONE)-BLOCK-POLY(PROPYLENE ADIPATE) COPOLYMERS

STAVROULA NANAKI, GEORGE PAPAGEORGIOU, DIMITRIOS BIKIARIS

Laboratory of Organic Chemical Technology, Department of Chemistry, AristoteleUniversity of Thessaloniki, GR-541 24, Thessaloniki, Macedonia, Greece –[email protected]

Abstract

Poly(ε-caprolatone)-block-Poly(propylene adipate) copolymers (PCL-b-PPAd copolymers) were synthesized by applying a combination of polycondensation to form propylene adipate oligomers first and then ring opening polymerization of ε-caprolactone. Such copolymers can be used in pharmaceutical technology, in applications such as drug delivery systems. The w/w copolymer compositions were (propylene adipate)/caprolactone 10/90, 20/80, 30/70, and 40/60. Molecular characterization included measurement of the intrinsic viscosities in CHCl3 solutions and measurement of molecular weight values using gel permeation chromatography (GPC). The degree of randomness was calculated from 1H-NMR and 13C-NMR spectra and the results verified the blocky character of the copolymers. WAXD patterns were also obtained, showing, that only the caprolactone blocks can crystallize. The isothermal and non-isothermal crystallization of neat PCL and the copolymers was studied with differential scanning calorimetry. The equilibrium melting points were estimated using the Hoffman-Weeks method. The ultimate attainable degree of crystallinity decreased with comonomer content. The isothermal crystallization rates were evaluated from the inverse of the crystallization half-times (1/t1/2) and they were found to decrease with increasing propylene adipate (PAd) comonomer content. The Avrami equation was used to analyze the isothermal crystallization data. The Modified Avrami equation, as well as the Ozawa model was used to study the non-isothermal crystallization kinetics. Also, the isoconversional method of Friedmann was elaborated to estimate the effective activation energy of non-isothermal crystallization (ΔΕ). The activation energy increased with increasing comonomer content in the copolymers, meaning that the crystallization is hindered by the presence of comonomer units along the chains. Table 1: Composition, Randomness factor (β) and the average number sequence lengths (Ln) of synthesized copolymers Polymer % wt % mol % mol 1H NMR % mol 13C NMRa β LnCl LnPAd PCL 0/100 0/100 0/100 0/100 PPAd/PCL 10/90 10/90 6.37/93.63 6.12/93.88 6.35/93.65 0.20 77.27 5.24 PPAd/PCL 20/80 20/80 13.28/86.72 12.97/87.03 13.07/86.93 0.18 43.38 6.52 PPAd/PCL 30/70 30/70 20.80/79.20 23.31/76.69 21.89/78.11 0.17 27.53 7.72 PPAd/PCL 40/60 40/60 29.00/71.00 43.13/56.87 41.37/58.63 0.13 18.05 12.74

a Estimated from the split of carbonyl carbons

30 32 34 36 38 40 42 44 46 48

0,00,20,40,60,81,01,21,41,61,82,02,2

PCL PCL-b-PPAd 90/10 PCL-b-PPAd 80/20 PCL-b-PPAd 70/30

1/t 1/

2 (m

in-1)

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0 20 40 60 80 100-300

-250

-200

-150

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-50

0

PCL PCL-b-PPAd 90/10 PCL-b-PPAd 80/20 PCL-b-PPAd 70/30 PCL-b-PPAd 60/40

∆Ε (K

J/m

ol)

Degree of Crystallinity (%)

Fig.1:Isothermal Crystallization rate vs temperature Fig.2: Activation energy of non isothermal for the PCL-b-PPAd copolymers crystallization vs crystallinity of copolymers


149

PI-63: IN SITU PREPARED POLY(PROPYLENE SUCCINATE) NANOCOMPOSITES USING FUMED SILICA AS FILLER: SYNTHESIS,

CHARACTERIZATION AND ENZYMATIC HYDROLYSIS. STAVROULA NANAKI, KRYSTALENIA ANDROULAKI, DIMITRIOS BIKIARIS

Laboratory of Organic Chemical Technology, Department of Chemistry, AristoteleUniversity of Thessaloniki, GR-541 24, Thessaloniki, Macedonia, Greece –[email protected]

Abstract

Poly(propylene succinate) (PPSu) nanocomposites were prepared through the in situ polymerization technique by the two step esterification and polycondensation method. As nanoparticle fumed silica (SiO2) was selected. SiO2 was introduced to vessel and mixed with the monomer prior to polymerization. The amount of fumed silica was added at concentrations of 0.25, 0.5, 1 and 2.5 wt% of the total polymerization mixture. Esterification of 1,3-prpanediol and succinic acid carried out at 190oC in the presence of Tetrabutyl Titanate as catalyst till total amount of produced H2O removed from polymerization vessel. Polycondensation carried out at 230oC and lasted 1, 2, 3 and 4 h for all the above concentrations. Prepared nanocomposites were charactacterized concerning molecular weight, morphology, mechanical properties and were also submitted in enzymatic hydrolysis. Molecular characterization conducted by intrinsic viscosity [η] measurements. It was found that low concentrations of SiO2, increased Mn values compared to that of net PPSu. Furthermore as polycondensation time increased, so Mn augmented. When filler concentration increased, Mn slitly decreased. SEM photos taken in order to reveal if dispersion occured. It was found that fumed silica particles remained spherical and diameter depended on its amount. Mechanical properties under tension were examined and showed that all nanoparticles induced a substantial enhancement of Young’s modulus and tensile strength compared to neat PPSu. DMA measurments also showed an increase in Storage Modulus. Using DMA and DSC, Tg values were recorded. Both measurments showed one Tg for all nanocomposites. From TGA analysis it was concluded that fumed silica accelerate the decomposition of PPSu, maybe due to hydrolytic reactions that the reactive groups on the surface of these materials can induce. An exception was the nanocomposite contained 1%wt SiO2, which showed a slit enhanced on thermal decomposition. Biodegradation study occured using phosphate buffer solution (pH = 7.4) containing 0.09 mg/mL Rhizopus delemar and 0.01 mg/mL Pseudomonas cepacia. The petries were then incubated at 30 ± 1oC in an oven for 23 days. Degree of enzymatic degradation was estimated from the weight loss analysis of samples as. It was found that as SiO2 amount increased, so biodegradation degree deducted.

0 1 2 3 40

5000

10000

15000

20000

25000

Mol

ecul

ar w

eigh

t (M

n) (g

/mol

)

Polycondensation time (h)

PPSu PPSu/SiO2 0.25 wt% PPSu/SiO

2 0.5 wt%

PPSu/SiO2 1 wt% PPSu/SiO

2 2.5 wt%

0,0 0,5 1,0 1,5 2,0 2,5-0,2

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0,8

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ile s

tres

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Pa)

Tensile strain (%)

PPSu PPSu/SiO2 0,25 wt% PPSu/SiO2 1 wt% PPSu/SiO2 2,5 wt%

0 5 10 15 20 25

0

20

40

60

80

100

Wei

ght l

oss

(%)

Time (days)

PPSu PPSu/SiO2 0.25 wt% PPSu/SiO2 0.5 wt% PPSu/SiO2 1 wt% PPSu/SiO2 2.5 wt%

Fig.1: Effect of SiO2 content Fig.2: Stress-strain curves of Fig.3: Weight loss caused on PPSu Mn PPSu/SiO2 nanocomposites by enzymatic hydrolysis


150

PI-64: THE EFFECT OF COMPOSITION AND PROCESSING PARAMETERS ON THE MORPHOLOGY AND PROPERTIES

OF ORGANOCLAY/POLYOLEFIN NANOCOMPOSITES GEORGE MORAITIS, PETROULA TARANTILI

Polymer Technology Lab., School of Chemical Engineering, National Technical University of Athens Heroon Polytechniou 9, Zographou, GR 15780 Athens, Greece – [email protected]

Abstract

Polymer/clay nanocomposites have been attracting a great deal of interest because of their improved mechanical, thermal and barrier properties, as compared with those of neat resin. However, in order to achieve the above mentioned standards, proper dispersion of organoclay in the polymer matrix and good interface between the two phases are essential. Since clays are highly organophilic, these goals are not always easy to achieve, especially for hydrophobic matrices like polyolefins (PO). As a result, various approaches have been followed to overcome the problems involved with the above parameters. These include modification of the clay surface by organo-intercalant to reduce the interaction between the clay platelets, while at the same time making them compatible with the polymer matrix, or the modification of PO matrix by adding a compatibilizer or the modification of both phases.

In this work, nanocomposites based on compatibilized polyolefin blends and organically modified montmorillonite (OMMT) nanoparticles, were prepared using melt mixing in a twin screw extruder. High density polyethylene (HDPE) and polypropylene (PP) blends were homogenized using a compatibilizer based on PE modified with maleic anhydride (MA-g-PE). Blends with 10, 25 and 35% (w/w) HDPE in PP were prepared in order to study the effect of HDPE on the dispersion of OMMT into polyolefin matrices. The following factors that affect nanocomposite structure were examined: (i) the extruder rotation speed, (ii) the compatibilizer content and (iii) the type of clay. In particular, compatibilizer concentrations of 5, 10 and 20 phr were studied. Four types of OMMT, with different organic modifications were used: Cloisite 15A, Cloisite 20A, Cloisite 25A and Cloisite 30B.

X-ray diffraction analysis was performed for the characterization of the obtained composite structures. Based on the above study, the screw rotation speed was set at 200 rpm and the concentration of compatibilizer in the polyolefins blend was 20phr. Cloisite 25A and Cloisite 30B were found the more effective reinforcements for preparation of intercalated or/and exfoliated structures, most probably due to the nature of their organic modification and further to its interactions with the compatibilized polyolefin matrix. It was also observed that lower concentration of HDPE and higher concentrations of compatibilizer resulted in a more efficient dispersion of OMMT in the polyolefin matrix. The optimum polyolefin blend compositions were reinforced with 1, 2 and 3 phr OMMT.

From DSC results it was observed that the incorporation of OMMT does not have any obvious effect on the melting (Tm) and glass transition (Tg) temperatures which remain almost constant. On the other hand, an increase in the melting enthalpy (ΔΗm) of PE at low OMMT concentration was observed, in comparison with the pure blend. This behavior was explained by the fact that exfoliated clay platelets act as nucleating agents, facilitating the heterogeneous crystallization process. However, at higher clay content the melting enthalpy of PE phase decreased, probably due to restrictions in the polymer chain mobility caused by the presence of reinforcement. From the results of TGA it was noticed that, in all the examined samples, the addition of OMMT decreases the temperature of higher degradation rate Tpeak, which can be attributed to the degradation of short molecular chains of intercalated agents. Tensile measurements showed that the addition of clay has no significant effect on the strength of all the examined nanocomposites, whereas the addition of Cloisite 30B improves the modulus of elasticity, especially for matrices prepared with 25/75 HDPE/PP blends. A slight improvement of modulus was observed in nanocomposites reinforced with Cloisite 25A.

In conclusion, preparation of compatibilized polyolefin blend/OMMT nanocomposites with twin screw extruder seems to run successfully at low clay levels. These nanocomposites present increased crystallinity, accompanied by an increase of the onset temperature of thermal degradation and stiffness, whereas their MFI values showed a decrease.


151

PI-65: THE EFFECT OF CLAY REINFORCEMENT ON THE MORPHOLOGY AND THERMOMECHANICAL PROPERTIES OF

MEDIUM MOLECULAR WEIGHT POLYSILOXANE NANOCOMPOSITES SOZON VASILAKOS, MARIANNA TRAINTOU, PETROULA TARANTILI


Abstract

Poly(dimethylsiloxane) (PDMS) is probably the most important and useful high performance elastomer, provided that its inherent mechanical weakness is overcome by reinforcement with some particulate fillers, usually silica and titania. The desired properties are usually reached at a low filler volume fraction, which allows the system to retain the homogeneity and low density of the polymer. Polymer/clay nanocomposites (NC, i.e. mixtures contining nanostructured filler particles) have recently attracted a great deal of interest because of their unique properties, such as improved mechanical performance, increased thermal stability, enhanced gas barrier properties and reduced flammability. NC of condensation type medium molecular weight polysiloxane rubber with and organically modified montmorillonite (OMMT) nanoparticles were prepared via sonication for effective dispersion of nanoparticles into the polymer matrix. Two types of commercial montmorillonite with different types of organic modification were studied: Cloisite 20A and Cloisite 30B. The incorporation of clay increases the rate of viscosity increase, during vulcanization of polysiloxane and decreases time required for complete reaction. Physical and chemical interactions among the cross-linker/accelerator system, polysiloxane matrix and clay reinforcement are responsible for this behaviour of the investigated NC. Using X-ray diffraction analysis it was shown that the featureless patterns for loadings of 1 to 3.5 phr for Cloisite 30B and 1-5 phr for Cloisite 20A NC, suggest that exfoliation or delamination hybrids were formed. Cloisite 20A is characterized by relatively high content of organic modifier and high intergallery spacing, which facilitates its intercalation in the PDMS matrix. In addition, it is possible that the hydrogenated tallow incorporated to Cloisite 20A enhances compatibility of the nanofiller with the silicone rubber system. The thermal stability of the investigated NC was assessed by means of TGA. A significant increase in the onset (Tonset) and maximum rate (Tpeak) temperatures of thermal degradation was observed, in comparison with unfilled PDMS. As the clay content in the NC increases, further improvement in resistance to thermal degradation is observeded. Cloisite 20A seems to be more effective for the improvement of thermal resistance of the NC. The incorporation of Cloisite 30B in PDMS does not have any obvious effect on the melting and glass transition temperatures, which remain almost constant, but the heat of fusion decreases. On the other hand, the addition of Cloisite 20A into PDMS reduces the crystallization temperature of the polymer. Melting temperature shows a slight decrease, whereas melting enthalpy presents significant decrease, starting from 1phr OMMT content but remains almost constant with further clay addition. The mechanical properties of pure polysiloxane seem to be significantly enhanced by the incorporation of the examined types of clay reinforcement. This indicates a very strong interfacial interaction between the polymer chains and the organically modified montmorillonite, in both cases. Raising the concentration of Cloisite 20A there is further improvement of mechanical properties. The difference between these two OMMT types is the organic modification. Cloisite 30B contain hydroxyl groups that probably affect the condensation reaction of the elastomer. This influences the crosslinking density and, consequently, the mechanical properties of NC. Swelling experiments with specimens from the reinforced silicone matrix (PDMS NC) immersed in toluene, exhibited a decrease in solvent uptake, as compared with samples corresponding to the unfilled PDMS matrix. Comparing NC having the same clay content it is observed that hybrids of Cloisite 20A have lower toluene uptake than that of Cloisite 30B. This behaviour can be probably due to the NC structure, i.e. the extent of exfoliation or intercalation of clay in the PDMS matrix.


152

PI-66: LAYERED SILICATE/POLY(LACTIC ACID) NANOCOMPOSITE FILMS AS CARRIERS IN DRUG RELEASE SYSTEMS

CHRISTINA STATHOKOSTOPOULOU, PETROULA TARANTILI


Abstract

Poly(lactic acid) (PLA) is a linear aliphatic thermoplastic polyester, readily biodegradable through hydrolytic and enzymatic pathways. PLAs are synthesized by ring-opening polymerization of lactides or by condensation polymerization of lactic acid monomers. Generally, commercial PLA grades are copolymers of poly(L-lactide) and poly(D,L-Lactide). The amount of D-enantiomers is known to affect the properties of PLA, such as melting temperature and degree of crystallinity. Upon in vivo degradation, PLA undergoes decomposition to lactic acid, a natural intermediate in carbohydrate metabolism, fully compatible and resorbable by human organisms. Materials based on PLA have gained wide acceptability for applications that require biocompatibility. Therefore, this polymer has received much attention in many biomedical applications, such as prosthetic devices and sutures, scaffolds in tissue engineering and drug delivery devices. In order to improve PLA’s physicochemical and mechanical properties and to control its degradation rate, different polymers as well as nanofillers of layered silicates, such as organically modified montmorillonites, have been studied. In this work, nanocomposites of D,L-PLA and organically modified montmorillonite (OMMT) containing 1-5 phr Cloisite 20A and Cloisite 30B, were prepared by the solution-intercalation film casting technique. Formation of mixed exfoliated and intercalated nanocomposite structures was confirmed by X-ray diffraction. An increase of glass transition temperature (Tg) of all the examined nanocomposites was recorded by Differential Scanning Calorimetry (DSC) experiments, due to physical hindrance of chain mobility after the incorporation of clay nanoparticles into the PLA matrix. The thermal stability of OMMT/PLA system was improved by the modified montmorillonite, as it was detected through thermogravimetric analysis (TGA). An increase in the onset of initial decomposition (Tonset) and a shifting of the maximum rate (Tpeak) of thermal degradation to higher temperatures were observed in comparison with pure PLA with increasing clay content up to concentrations of 3 phr. Changes were also found in the peak of the rate of weight change versus temperature. This behaviour can be attributed to the increased thermal stability of clay, which was further enhanced by interactions between clay particles and polymer matrix.

The incorporation of Cloisite 20A seemed to cause a decrease in the molecular weight of PLA. This might be due to chain scission initiated by the sonication mixing process. On the other hand, the addition of Cloisite 30B at concentrations above 1phr was found to increase molecular weight, which could probably be attributed to physicochemical interactions of the polymer chains with hydroxyl groups present in the organic modification of this type of montmorillonite.

Furthermore, the in vitro study of degradation of PLA nanocomposite films in deionized water, indicates the complexity of this process. The release of Guaifenesin [GFN] from pure PLA and PLA nanocomposite films, reinforced with 2 phr Cloisite 20A and Cloisite 30B, was studied. The examined PLA specimens were loaded with 5 and 10 phr GFN and were immersed in deionized water at 37oC. In the case of specimens loaded with 5 phr GFN, the nanocomposites showed a slight higher release rate in comparison with pure PLA systems especially in the early stages of the experiment. A significant increase of drug release rate was observed in the case of PLA hybrids loaded with 10 phr GFN, in comparison with unreinforced PLA fims. The higher amount of the examined hydrophilic drug, possibly promoted interactions with the hydrophilic layered silicate reinforcement faciliting the release process from PLA matrix.

In conclusion, the incorporation of OMMT in PLA matrices appears a novel and promising technique, that can be applied as a means improve properties and control the release rate of pharmaceutical substances in aqueous environment.


153

PI-67: SYNTHESIS AND CHARACTERIZATİON OF AMPHIPHILIC POLYMER COMPOSITES CONTAINING INORGANIC NANO CLUSTERS

1ÖZLEM A. KALAYCI, 1TURGAY ATALAY, 2*BAKİ HAZER 1Department of Physics, Zonguldak Karaelmas University, Zonguldak 67100 (Turkey)-

[email protected]; [email protected] 2 Department of Chemistry, Zonguldak Karaelmas University, Zonguldak 67100 (Turkey) Phone: 0372 2574010-1372. E-mails: [email protected]; [email protected]

Abstract

The interest in the synthesis and characterization of nanoparticles [1] embedded amphiphilic block and graft copolymers [2] has increased recently due to their possible applications in the fields of biology and material sciences. Size provides important control over many of the physical and chemical properties of nanoscale materials including luminescence, conductivity, and catalytic activity allowing application of these species in optical systems, catalysis, and biomedical technology. This work refers preparation and physical characterization of some new organic-inorganic composites. Polyethylene glycol-polypropylene amphiphilic graft copolymer (PEG-g-PP) was synthesized by the reaction between chlorinated polypropylene and polyethylene glycol with Mn 2000 and 4000 g/mol [3]. Preparation and optical characterization of the Sb2S3, SiO2, Au, Ag, CuS or CdS nano particles embedded in this amphiphilic comb-type graft copolymers have been described.

Scheme 1 Synthesis of PP-g-PEG amphiphilic comb-type graft copolymers.

20 30 40 50 60 70 80 90

450

Nanocomposite

310

2θ

Cou

nt.

PP-g-PEG

Figure 1. Fluorescence spectra of Figure 1. XRD pattern of the the PP-g-PEG/SiO2 nanoparticles Sb2S3/PP-g-PEG nanocomposite. nanoparticles. Acknowledgment We would like to acknowledge TÜBİTAK for the grant provided for this study [grant no. 108T423], including financial support for travel expenses, and The Commission of Zonguldak Karaelmas University Scientific Research Projects (grants# 2008-70-01-01 and 2008-13-03-01). References [1] Alivisatos AP (1996) J Phys Chem 100:13226 13239 [2] Hadjichristidis N, Pitsikalis M, Pispas S, Iatrou H (2001) Chem Rev 101:3747–3792 [3] (a) Kalaycı Ö A, Cömert F B, Hazer B, Atalay T, Cavicchi K A, Çakmak M. (2010) Polym. Bull. 65: 215-226. (b) Kalaycı Ö A, Hazer B, Atalay T (2010) Tr J. Chem (in press).


154

PI-68: SYNTHESIS AND CHARACTERIZATION OF POLYLACTIDE-G-POLY (ETHYLENE GLYCOL) BRUSH TYPE GRAFT COPOLYMERS

GÖKHAN ÇAVUŞ, *BAKİ HAZER

Department of Chemistry, Zonguldak Karaelmas University, Zonguldak 67100 (Turkey) Phone: 0372 2574010-1372.E-mails: [email protected]; [email protected]

Abstract The synthesis, properties, and degradability of biodegradable polymers have been reported over the past decades. In particular, aliphatic polyesters such as Poly (L-Lactide), PLLA, have attracted much attention as biomedical materials are available from renewable sources, and degrade completely to nontoxic water and carbon dioxide. However, there is still a great need to improve other properties as thermal, mechanical and water uptake properties for increasing the scopes of biomedical or environmental plastic fields, its copolymerization with other monomers or polymers. We have attempted to obtain poly (ethylene glycol), PEG, gafted on PLLA comb type graft copolymer. For this purpose, chlorination of PLLA was carried out by passing chlorine gas through its CCl4 solution, according to the same reaction performed with bacterial polyesters in our laboratories, recently. Chlorinated PLLA was reacted with PEG in the presence of a base catalyst in tetrahydrofuran solution. Graft copolymer obtained was blended with PLLA and the products were characterized by 1H NMR, FTIR, GPC, DSC, water uptake and mechanical test techniques.

Acknowledgment We would like to acknowledge TÜBİTAK for the grant provided for this study [grant no. 108T423], including financial support for travel expenses, and The Commission of Zonguldak Karaelmas University Scientific Research Projects for grants. References [1] Kaplan DL (1998) Biopolymers from Renewable Resources; Springer Verlag: New York. [2] Thi TH, Matsusaki M, Akashi M (2009) Biomacromolecules 10, 766–772. [3] Arkin AH, Hazer B, Borcakli M (2000) Macromolecules 33, 3219-3223.


155

PI-69: NOVEL COMB TYPE AMPHIPHILIC GRAFT COPOLYMERS VIA THIOL-ENE CLICK REACTIONS

ELİF KELEŞ, BAKİ HAZER

Department of Chemistry, Zonguldak Karaelmas University, Zonguldak 67100 (Turkey) [email protected]; [email protected]

Abstract

Functionalization of the polymers as a useful methodology for the generation of new materials with wide range of applications. In our laboratories, we have recently reported graft copolymers of polybutadiene as amphiphilic cross-linked elastomers. Thiol-ene chemistry has very recently emerged as a versatile and very efficient tool for the functionalization of polymers. Now, we want to report the synthesis and characterization of a novel comb type amphiphilic copolymer obtained from poly (ethylene glycol) (PEG) and commercially available poly(styrene) (PS)-b-poly (isoprene) (PI)-b-PS. For this purpose, PEG was reacted with mercapto propionic acid to produce PEG with mercapto end group (PEG-SH). Then, double bonds of PS-b-PI-b-PS were capped with PEG-SH in the presence of a free radical source (e.g. AIBN). The reaction scheme is shown below:

Amphiphilic comb type graft copolymers were characterized by 1H NMR, FTIR, GPC; SEM and thermal analysis technics. Acknowledgment We would like to acknowledge TÜBİTAK for the grant provided for this study [grant no. 108T423], including financial support for travel expenses and The Commission of Zonguldak Karaelmas University Scientific Research Projects for grants. References [1] Boaen N, Hillmyer MA (2005) Chem Soc Rev 34, 267. [2] Hazer B (1995) Macromol Chem Phys 196, 1945. [3] Lutz, J.-F.; Schlaad, H. Polymer 2008, 49, 817–824. [4] Gitsov I, Wooley KL, Frechet JM (1992) Angew Chem Int Ed 31, 1200. [4] Wesslen B, Wesslen KB (1989) J Polym Sci, Part A: Polym. Chem. 27, 3915. [5] Gao H, Matyjaszweski K (2007) J Am Chem Soc 129, 6633. [6] (a) Balcı M, Allı A, Hazer B, Güven O, Cavicchi K, Cakmak M. (2010) Polym Bull 64, 691. (b) Kalaycı OA., Hazer B., Atalay T., Cavicchi K, Cakmak M. (2010) Polym Bull 65, 215. [7] Hadjichristidis N, Pitsikalis M, Pispas S, Iatrou H (2001) Chem Rev 101, 3747.


156

PI-70: THERMALLY STABLE AND ORGANOSOLUBLE POLYESTERS CONTAINING NAPHTHALENE GROUPS: SYNTHESIS AND PROPERTIES

JAFAR ATTAR GHARAMALEKI1 1Young Researchers Club, Islamic Azad University, North Tehran Branch, Tehran (Iran)

[email protected]

Abstract

Polyesters (PEs) are one of the most versatile polymers. They contain widely different materials with large applications, which are produced by a variety of manufacturing techniques. They have in common the ester group in the main chain, which is a polar group and brings about inter and intramolecular chain interactions that may reflect in some properties such as low solubility, mobility of the chain and melting characterizations. In addition, PEs often have limited heat and flame resistance, so these materials are inappropriate for many important applications. Several approaches have been proposed to develop structurally modified polymers having increased solubility, in order to improve their processability while maintaining a good thermal stability, based on the incorporation of flexible segments bearing ester, sulfone, amide, ether and sulfide moieties in the polymer backbone, without sacrificing heat resistance.1,2 Also, major enhancement in processability can be achieved by modifying the substitution pattern of the aromatic units in the main chain, especially by inclusion of 1,2-linked units derived from ortho-catenated aromatic rings.3 In addition, the presence of thioether linkages can induce important new properties, such as less water absorption, better fire-retardant properties, and higher refractive indices for the resulting polymers. This work deals with the synthesis and characterization of novel series of ortho-sulfide bridged poly(sulfide ester)s (PSE)s by the polycondensation reactions of a sulfide containing diol (1,1'-thiobis(2-naphthol)) (TBN) with various aromatic diacids. The resulting new polyesters were obtained in good yields and possessed inherent viscosities in the range of 0.68–1.03 dL g–1. All of the polymers were amorphous in nature and showed excellent solubility. They showed good thermal stability with the glass transition temperatures between 223-285 °C, the 10% weight loss of 451–507 °C in nitrogen and 443–501 °C in air, and the residue at 700 °C of 44–59% in nitrogen.

SO O C

O

Ar C

OSHO OH

TBN

+ Ar CC

O

Cl

O

Cl180 °C, 20 h.

n

Ar : (1) (2) (3) (4)

N

N

(5)

N

O(6) (7)

PSE-1 PSE-7

TEA.HCl / DCB

1 Liaw, D. J.; Hsu, J. J.; Liaw, B. Y. J. Polym. Sci., Part A: Polym. Chem. 2001, 39, 2951–2956. 2 Zhang, P.; Linbo ,W.; Bo-Geng, L. Polym. Degrad. Stab. 2009, 94, 1261–1266. 3 Berti, C.; Celli, A.; Marianucci, E.; Vannini, M. Eur. Polym. J. 2007, 43, 2453–2461.


157

PI-71: DRUG DELIVERY KINETICS OF POLYACRYLAMIDE-CO-ITACONIC ACID/CHITOSAN HYDROGELS

ALEJANDRO GONZÁLEZ-ÁLVAREZ1, JUAN C. SÁNCHEZ-DÍAZ1, LUIS E. CRUZ-BARBA1, FAUSTO BECERRA-BRACAMONTES2, AGUSTÍN MARTÍNEZ-RUVALCABA1

1Department of Chemical Engineering, University of Guadalajara, Blvd. García Barragan #1421, 44430 Guadalajara (Mexico) – [email protected]

2Department of Chemistry, University of Guadalajara, Blvd. García Barragan #1421, 44430 Guadalajara (Mexico)

Abstract

Hybrid polymeric networks composed of polyacrylamide and chitosan were developed to determine their ascorbic acid delivery kinetics at various chitosan concentrations. The hybrid acrylamide/chitosan hydrogels were synthesized in aqueous itaconic acid solution (1% w/w). Prior to the drug-release experiments, were performed swelling experiments in order to determine the swelling mechanisms; were carried out using three different pH solutions: acidic (pH 4 buffer solution), neutral (distilled water) and basic (pH 10 buffer solution). The results of the swelling study showed that the swelling properties of the network varied with the changes of the pH in the swelling solution, as well as concentration of chitosan. The results indicated that the swelling process followed a second order kinetics. The ascorbic acid diffusion inside the hydrogel follows a Fickian mechanism. The ascorbic acid diffusion coefficients are reported as a function of chitosan concentration. In acidic medium the swelling capacity decreases due to the chitosan NH+

3 groups that is ionically linked with the itaconic acid COO- group, and this ionic bond increases the crosslinking density. In aqueous medium, the NH+

3 group loses a proton and becomes NH2, thus reducing the crosslinking density. In basic medium the swelling capacity decreases relative to the aqueous medium, because the itaconic acid is ionized and is forming hydrogen bonds with the nitrogen of the amine groups. The swelling of the hydrogels follows a second order kinetics, and the swelling rate constants obtained confirm the presence of different polymer-solution interactions in the system, which do not exist in the chitosan-free hydrogel. The ascorbic acid release follows Fick’s second law of diffusion, and the characteristic power, n, is about 0.5. The kinetic constant (k1) and the diffusion coefficients decrease when the chitosan concentration in the hydrogel is increased, mainly due to a rise in the crosslinking density and a decrease on the volume of free spaces available in the hydrogel. The diffusion coefficients are between 10-5 and 10-6 cm2/s, which suggest that the hydrogels studied have a good potential for their use in applications such as drug release, since similar values have been reported in papers with a pharmaceutical approach.


158

PI-72: EFECT OF INTERFACIAL INTERACTION ON DENSITY DISTRIBUTION INSIDE THE PHOTORESIST THIN FILMS INVESTIGATED BY X-RAY

REFLECTIVITY METHOD

JIN GOO YOON1, JUNG-HOON KIM1, WANG-CHEOL ZIN1, JAE HYUN KIM2, SUNG IL AHN2, JAEHYUN KIM3, JAE-WOO LEE3

1Department of Materials Science and Engineering, Pohang University of Science and Technology, San 31, Hyoja-Dong, Nam-Gu, Pohang, Gyeongbuk, 790-784, Korea – [email protected] 2Manufacturing Technology Team, Infra Technology Service Center, Device Solution Business,

SAMSUNG ELECTRONICS CO.,LTD San #16 Banwol-Ri, Taean-Eup, Hwasung-City, Gyeonggi-Do, 445-701, Korea

3Dongjin Semichem CO., Ltd., 625-3 Yodang-Ri, Yanggam-Myun, Hwasung-Si, Gyeonggi-Do, 445-931, Korea

Abstract

In the lithography technology by Top-down method, role of polymers that are used as photoresists becomes more significant as the pattern size decreases. Generally, the photoresist(PR) consist of a base polymer, additives such as photo acid generator(PAG) and quencher. These PR film homogeneity is thought to be the key requirement of resist materials to obtain high resolution and sensitivity and low line width roughness (LWR). In this study, vertical electron density profiles of model PR(consist of base polymer and PAG) film on bare and self-assembled monolayers (SAMs)-modified Si substrates were obtained using X-ray reflectivity analysis. Small amount of density fluctuation at each depth of film could be analyzed with DWBA (distorted wave Born approximation) fitting technique. The density of base polymer near the interface at Si substrate is slightly depleted, whereas that at SAMs-modified Si substrate is relatively homogeneously distributed. These results indicate that the density distribution inside PR film is affected by the interfacial properties between the PR film and the substrate. The approximate distributions of PAG were obtained from the comparison between the density distribution of model PR and base polymer. Distributions with low concentration of PAG (2wt%) show that the PAG molecules tend to be concentrated near the surface or interface of film, while in the case of 10wt % concentration is comparatively homogeneously distributed. It is found that these trends in density distributions varied by concentration of PAG are also affected by the density distribution of base polymer.


159

PI-73: CONTROLLED HOLLOW SPHERES OF POLY(METHOXYANILINE) OBTAINED THROUGH A SELF-ASSEMBLY METHOD

LIJUAN ZHANG, JING SUI, PAUL A. KILMARTIN, AND JADRANKA TRAVAS-SEDJEC Polymer Electronics Research Centre, Chemistry Department, The University of Auckland,

Private Bag 92019, Auckland, New Zealand

Abstract

Polyaniline (PANI) nanostructures have recently received considerable attention due to its easy of preparation, good environmental stability and potential application in nanoelectronic devices. However, many published PANI nanostructures has no good properties though their special nano-morphology. Its derivatives nanostructures have attract much attention because of the existence of functional group.

This presentation will report the effect of the methoxy-substituent on aniline monomer on the morphology and properties of produced polymer obtained via a self-assembly process. Moreover, the size and properties of poly(o-methoxyaniline) hollow spheres could be controlled through the change of dopant. The morphologies of the reaction products were measured by SEM (Figure 1). The size of the hollow spheres can be changed from microspheres (Figure 1A) to nanospheres (Figure 1B) by changing the dopant from p-toluenesulfonic acid to poly(methyl vinyl ether-alt-maleic acid). Their structural features were characterized by FTIR, Raman spectra and XRD. Also, the cast film of poly(o-methoxyaniline) hollow spheres shows high electric-catalytic activity to ascorbic acid. Moreover, the size of hollow spheres has significant influence on the electric-catalytic activity to ascorbic acid.

Figure 1A Figure 1B


160

PI-74: OPTIMIZATION OF THE MECHANICAL PROPERTIES OF HDPE/EVA NANACOMPOSITE USING TAGUCHI METHOD

MOHAMADHADI PIRZADEH 1, ALIZERA SHARIF 1,2,*, MOHAMADREZA KALAEE 1

AND SHAHIN AKHLAGHI 1 1 Department of Polymer Engineering, Islamic University of Azad, Tehran South Branch,

Abozar Blvd. Ahang 1777613651 Tehran (Iran) 2 Department of Polymer Science and Technology, Research Institute of Petroleum Industry (RIPI),

4th Km Karaj highway 1693913154 Tehran (Iran) - [email protected]

Abstract

Polyethylene (PE)/ethylene-co-vinyl acetate (EVA) blends are among the most important commercial polymeric systems which have been widely employed in various applications such as shrinkable films, multilayer packing, wire and cable insulation coating 1-3. Recently, the application of nanosized fillers such as nanoclay has been suggested as a beneficial strategy towards PE/EVA blends with improved properties 4,5. In this research work, high density polyethylene (HDPE)/EVA/organoclay nanocomposites were prepared by melt blending method. Mechanical properties of various nanocomposite formulations containing polyethylene-g-maleic anhydride as a compatibilizer and/or Irganox 1010 as a stabilizer were investigated. It was shown that the nanocomposite formulations including both the compatibilizer and the stabilizer possessed the highest mechanical properties. This can be attributed, in one hand to the better interactions between the polymers and the organoclay in the compatibilized samples. On the other hand, it was suggested that the stabilizer prevented or at least reduced the thermo-oxidative degradation of the clay modifier, which in turn contributed to the mechanical properties enhancement. Also, the Taguchi method was employed through a L16 orthogonal array that includes sixteen rows and three columns in order to determine the level of the nanocomposite constituents leading to the optimum mechanical properties. Accordingly, the optimum properties were observed at 3 phr of the organoclay, 6 phr of the compatibilizer and 2 phr of the stabilizer.

1 Shi X, Jin J, Chen Sh, Zhang J. Journal of Applied Polymer Science 2009;113:2863–2871. 2 Basfar AA, Mosnacek J, Shukri TM, Bahattab MA, Noireaux P, Courdreus A. Journal of Applied Polymer Science 2008;107:642–649. 3 Haurie L, Fernandez AI, Velasco JI, Chimenos JM, Cuesta JML, Espiell F. Polymer Degradation and Stability 2007;92:1082-1087. 4 Riahinezhad M, Ghasemi I, Karrabi M, Azizi H. Polymer Composites 2010;2:56-80. 5 Scapini P, Figueroa CA, Amorim CLG, Machado G, Mauler RS, Crespoa JS, Oliveira RVB. Polymer International 2010; 59:175–180.


161

PI-75: PERMEABILITY OF POLYMER/CLAY NANOCOMPOSITES

G. CHOUDALAKIS* AND A. D. GOTSIS Department of Sciences, Technical University of Crete,

73100, Hania, Greece

Abstract

The presentation focuses on the barrier properties of polymer nanocomposites. The basic ideas on permeability reduction due to the inorganic nanoparticles are presented, as well as some of the existing theoretical models. The predictions are tested with the available experimental results, where it seems that the Nielsen model is sufficient for most cases. Deviations from the expected/predicted results are reported and explained on the basis of alterations of the free volume in the polymer matrix due to the presence of the clay particles. These features concern not only the total free volume variations but also its distribution over the free volume hole sizes. Experimental data that support the above arguments are reported. It seems that the barrier properties of polymer nanocomposites are affected not only by the difficulties of particle exfoliation but also by their interactions with the matrix, which may alter physical features of the polymer and in some cases they may lead to barrier properties deterioration. *Author to whom correspondence should be addressed, [email protected]


162

PI-76: SYNTHESIS OF POLY(URETHANE)S BASED ON DIPHENYL-SYLANE/GERMANE AND OXYARENE UNITS. STRUCTURE-PROPERTIES

RELATIONSHIP A. TUNDIDOR-CAMBA, C.A TERRAZA, L.H. TAGLE, C.M. GONZALEZ-HENRIQUEZ

Organic Chemistry Department, Faculty of Chemistry, Pontificia Universidad Católica de Chile, Box 306, Post 22, Santiago, Chile

[email protected], [email protected], [email protected], [email protected] INTRODUCTION

Condensation polymers are materials with wide applications in several fields of the industry1,2. Thus, poly(urethane)s (PUs) and others materials are employed for producing articles with different electrical, mechanical and chemical properties. In this work, we report the synthesis of PUs containing Si/Ge atoms and oxyarene units in the main chain. The incorporation of the heteroatoms in the polymer structure implies polarity due to the difference of electronegativity between heteroatom and C atom, which increase the thermal stability3. Both heteroatoms and ether linkages increase flexibility, causing a decrease of the Tg values and an increase of the solubility in common organic solvents. On the other hand, the ether links gives high transparency in the UV-visible region4. In this sense, we present the synthesis of PUs derived from several bis(chloroformates) containing Si or Ge bonded to aliphatic or aromatic groups and the diamine 4,4'-(4,4'-(9H-fluorene-9,9-diyl)bis(2-methyl-4,1-phenylene))bis(oxy)dibenzenamine. Also, we synthesized a PU without heteroatom in the main chain to compare the properties. Monomers 4,4’-(R1R2silylene)bis(phenylchloroformates), where R1=R2=Me or Ph, 4,4’-(diphenyl-germylene) bis(phenylchloroformates) and 4,4’-(dimethyl_ methylene)bis(phenylchloroformates) were synthesized according to described procedures5. Diamine 4,4'-(4,4'-(9H-fluorene-9,9-diyl)bis(2-methyl-4,1-phenylene))bis(oxy) dibenzenamine (1) was synthesized according to scheme 1. Poly(urethane)s A toluene solution of the bis(chloroformate) derivate was added dropwise over a toluene solution of diamine (1) and pyridine. The mixture was stirred during 30 min. at room temperature. Then, the suspension was poured into methanol. The polymer was filtered, washed several times with methanol and dried until constant weight (scheme 2).

Scheme 2. Synthesis of poly(urethane)s. I: W= Si, R1=R2=Me or Ph. II: W=Ge, R1=R2=Ph. III: W=C, R1=R2=Me.

Scheme 1. Synthesis of the diamine (1). All polymers were characterized by inherent viscosity, IR and NMR spectroscopy, including 29Si-NMR when appropiate. The thermal characterizations were carried out by DSC and TGA. The UV-visible analysis showed high values of transparency for the polymers. ACKNOWLEDGEMENTS: Authors acknowledge the financial assistance by Fondo Nacional de Investigación Científica y Tecnológica, FONDECYT, through Project 1095151. A.T. thanks CONICYT for a fellowship. 1 Mittal K.L., Polyimides: Synthesis, Characterization and Applications, Plenum, New York, (1984). 2 Abade M.J.M. Ed., Polyimides and other High-Temperature Polymers, Elsevier, New York, (1984). 3 Bruma M., High performance polymers containing phenylquinoxaline and silicon in the main chain. Rev Roumaine Chim 52:309, (2007) 4 Yang, C. P.; Lin, J.H. J Polym Sci Part A Polym Chem, 31, 2153. (1993) 5 Terraza CA, Tagle LH, Concha F, Poblete L., Desiged Monom. Polym., 10 (3), 253, (2007).

CH3 CH3OHHO

K2CO3 anh

Cl NO2

CH3 CH3OO

O2N NO2

CH3 CH3OO

H2N NH2

HydrazinePd/C

(1)

(1)

W

R1

R2

OOHNNHWO O

CCO OR1

R2

**Toluene

Py

OOC

CO

O

ClCl


163

PI-77: POLY(IMIDE-DIAMIDES) CONTAINING SILICON IN THE MAIN CHAIN. SYNTHESIS AND CHARACTERIZATION

L.H. TAGLE, C.A. TERRAZA, D. COLL, A. TUNDIDOR-CAMBA

FACULTAD DE QUIMICA, PONTIFICIA UNIVERSIDAD CATOLICA DE CHILE, P.O. BOX 306, SANTIAGO, CHILE ([email protected])

INTRODUCTION

Poly(amides) and poly(imides) are condensation polymers and high performance materials with superior thermal and mechanical properties, which make them useful for advanced technologies1. The introduction of flexible units2, the use of meta-oriented groups3 or the presence of several functional of bulky groups4, can produce soluble polymers with low Tg values but maintaining good thermal properties. On the other hand, the introduction of heteroatoms such as Si in the main chain, implies an electronic transport and an increase of the solubility due to the ionic character of the C-Si bond5. In this work we present the synthesis and characterization of poly(imide-diamides) derived from an aromatic diacid substituted by a group containing both, imide and amide groups derived from phthalic anhydride and amino-acids as flexible units.

METHODS Monomers 5-(2-phthalimidyl-R-ylamino) - isophthalic acids were obtained from 5-amino-isophthalic acid and 2-phthalimidyl-R-acids according to described procedures6. The 2-phthalimidyl-R-acids were synthesized from phthalic anhydride and the following amino-acids: glycine, L-alanine, L-phenylalanine, L-valine, L-leucine, L-isoleucine and 4-aminobenzoic. The diamine bis(4-aminophenyl)-diphenylsilane was obtained according to a described procedure7. Poly(imide-diamides) Polymers were obtained from the diacids and the diamine in N-methyl-2-pyrrolidone (NMP) with triphenyl phosphite (TPP), pyridine and calcium chloride. The mixture was stirred at 120 ºC and precipited in methanol. Polymers were filtered, washed, dried until constant weight and characterized

RESULTS Polymers were obtained according to the following scheme:

N

O

O

R COOH

N

O

O

R

HOOC COOH

NH2

2)

1) SOCl2

NH

COOH

COOH

H2N Si

C6H5

C6H5

NH2

Poly(imide-diamide)

CO

Where R: CH2; CH(CH3); CH(CH2-C6H5); CH-CH(CH3)2; CH-[CH2-CH(CH3)2]; CH(CH-CH3)-CH2CH3; p-C6H4. Poly(imide-diamides) were characterized by IR and 1H, 13C and 29Si NMR spectroscopy and inherent visicosities. The thermal properties, DSC and TGA, were obtained and related to the polymeric structures.

ACKNOWLEDGEMENTS Authors acknowledge the financial support by Fondo Nacional de Investigación Científica y Tecnológica, FONDECYT, through Project 1100015. D.C. thanks CONICYT for a fellowship. 1 P.E. Cassidy, “Thermal Stable Polymers”. Synthesis and Properties”, Marcel Dekker, 1980. 2 S. Mallakpour and E. Kowsari, Polym. Adv. Technol., 16, 732 (2005). 3 D.J. Liaw and B.Y. Liaw, Polymer, 42, 839 (2001). 4 I. Sava and M. Bruma, Macromol. Symp., 239, 36 (2006). 5 M. Bruma and B. Schulz, J. Macromol. Sci., Polym. Rev., 41C, 1 (2001). 6 S. Mallakpour and S. Sepehri, Poly. Adv. Technol., 19, 1474 (2008). 7 J.R. Pratt, W.D. Massey, F.H. Pinkerton and S.F. Thomas, J. Org. Chem, 40, 1090 (1975).


164

PI-78: SYNTHESIS OF POLYETHYLENE GLYCOL BASED HYDROGEN BONDED SIDE CHAIN LIQUID CRYSTAL POLYMERS

ESRA ERBİLA, CEREN AYTAÇA, YEŞIM GÜRSELA, BAHIRE FILIZ ŞENKALA,

FAHRETTIN YAKUPHANOĞLUB

Aİstanbul Teknik Üniversitesi, Fen-Ed. Fak., Kimya Böl.,34469, Maslak/İstanbul

BFırat Üniversitesi, Fen-Ed. Fak., Fizik Böl., Elazığ

[email protected], [email protected],,

Recently, synthesis of side chain liquid crystal polymers in which combine the properties of low molecular weight liquid crystals and polymers, have become essential research topic for their interesting electrical and optical properties. Because of their properties, their usage is very important at microelectronic cycle application for instance, optical data storage[1] and non-linear optic[2].. In this study, Polyethylene glycol (PEG) based hydrogen bonded side chain liquid crystal polymers (HB-PLC) were synthesized by using PEG modified with dioctylamine and cyanobiphenyl mesogens having different number of methylene units as a hydrogen bond acceptor and hydrogen bond donor respectively.

CH2 CH2On

NN H2COn

H CNOH2C On HOCN

Scheme1. The structure of Polyethylene Glycol Based Hydrogen Bonded Side Chain Liquid Crystal

Polymer (HB-PLC).

The formation of H-bond was confirmed by using FTIR spectroscopy. The liquid crystalline behavior of the HB-PLC was investigated by differential scanning calorimeter (DSC) and polarized optical microscopy (POM). [1] ] M. Trollsas, F. Sahlen, U. W. Gedde, A. Hult, D. Hermann, P. Rudquist, L. Komitov, S. T. Lagerwall, B. Stebler, J. Lindstrom and O. Rydlund, Macromolecules 1996, 29, 2590-2598. [2] X. Meng, A. Natansohn, C. Barretl and P. Rochon, Macromolecules 1996, 29, 946. This work was supported by the Turkish Scientific and Technological Research Council of Turkey (TUBİTAK) (Project Number: 108T722). Authors wishes to thank TÜBİTAK.


165

500 600 700 800

0,00

0,06

0,12

0,18

0,24

0,30

610

48 hours 30 hours 24 hours 6 hours 3 hours 1 hours few minutes

after immersion

Abs

orba

nce

Wavenumber, nm

660

UV-Vis absorption

PI-79: RELEASE OF ACTIVE AGENTS FROM POLYMERS: FAST QUANTITATIVE ASSESSMENT AT LOW CONCENTRATION VIA SERS

JOHN ANASTASOPOULOSa,b, A. MANIKASa,b, A. SOTOa,b and G. VOYIATZISa,b

aFORTH/ICE-HT, P.O. Box 1414, GR-265 04, Rio-Patras (Hellas) - [email protected] bInterdepartmental Program of Graduate Studies on “Polymer Science and Technology”,

University of Patras, GR-265 00, Rio-Patras (Hellas) Abstract

The application of polymeric materials for biomedical purposes is growing very fast in diverse fields such as tissue engineering, implantation of medical devices and artificial organs, prosthesis, ophthalmology, dentistry, bone repair, chemotherapy.1 Polymer-based delivery systems enable controlled slow release of drugs into the body and also they make possible targeting of drugs into sites of inflammation or tumors. Thus, biopolymer-mediated chemotherapy has shown promising results in the treatment of brain tumors. Intratumoral biopolymer-mediated drug delivery remains a challenge for the treatment of immune-depressed patients by delivering the drug into the tumor bed, minimizing systemic toxicity. Since drugs need to be quantified for drug delivery system characterization, intracellular distribution studies, free or vehicular, and for pharmacokinetic assays, the most suitable quantification method must be chosen. It should have a high sensitivity, specificity and reproducibility, and should be capable of measuring at very low concentration range, as well.

In the present study, two analytical techniques are utilized to quantitatively evaluate the antineoplastic drug Mitoxantrone and the antifungal agent Ambisome (Amphotericin b) released from active agents-loaded biocompatible polymer matrices PP, EVA, PLGA; the UV-Vis absorption and, for the 1st time, the Surface Enhance Raman Scattering (SERS). SERS is a new, versatile, fast and non destructive tool for the estimation of extremely small amounts of substances. Due to the enhancement provided to the Raman signal by the nano-rough noble-metal substrates or the nano-structured colloidal clusters of noble metals, even single molecule detection has been reported. Therefore, applying SERS to extremely low concentration measurements proves to be challenging.2

Fig. 1. Mitoxantrone released from PP+Mitoxantrone 0.47% w/w specimens in water via

(a) UV-Vis & (b) SERS using oscillating cell and Ag nanocolloidal solution with the PLS analysis as an inset

Drug (Mitoxantrone) loaded polymer (PP) specimens were prepared and the in vitro drug release was determined in water (Fig 1). Fast SERS quantitative measurements showed enhanced sensitivity (RMSE: 150 pg/mL) compared to the UV-vis absorption; SERS may enable low concentration quantitative assessment of controlled release of drugs from biopolymer-based delivery systems.

1 M Saini, F Roser, S Hussein, M Samii and M Bellinzona, “Intralesional Mitoxantrone biopolymer-mediated chemotherapy prolongs survival in rats with experimental brain tumors” J Neuro-Oncol 68, 225-232 (2004). 2 AC Manikas, A Soto Beobide and GA Voyiatzis, “Quantitative analysis by Surface Enhanced Raman Scattering utilizing an oscillating-cell and right angle collection geometry” Analyst 134, 587-592 (2009).

0 5 10 15 200

5

10

15

20

RMSE=0.15 ng/mL

Pred

icte

d co

ncen

tratio

n, n

g/m

L

True concentration, ng/mL

R2=99,93PLS analysis

1050 1200 1350 1500 1650

48 h 30 h 24 h 6 h 3 h 1 h few min

after immersion Ag colloid

λο=632.8 nmt=1 sec

Rel

ativ

e In

tens

ity

Ram an Shift, cm -1

SERS

1300


166

PI-80: EFFECT OF DRAWING CONDITIONS ON MOLECULAR STRUCTURES AND PHYSICAL PROPERTIES OF BICOMPONENT FIBERS

TAE HWAN OH, SUNG SOO HAN, WON SEOK LYOO, YOUNG HO SEO

School of Textiles, Yeungnam University, 214-1 Daedong, 712749 Gyeongsan, Korea – [email protected]

Abstract

Conjugate fiber spinning is one of the most useful methods for functional fiber production. Unlike conventional fibers, functional fibers have been widely used in various fields such as medical, automotive, architectural, and electrical. In this work, as-spun poly(trimethylene terephthalate) (PTT)/poly(ethylene terephthalate) (PET) side-by-side conjugate fibers were drawn at various drawing conditions and the effects of these conditions on the structure change and physical properties of the fibers were examined. Effects of draw ratio and heat-set temperature were observed. The PTT/PET conjugate fibers showed well-developed curls without treatment in boiling water. In the state of an as-spun fiber, the molecular orientation of PTT was higher than PET, whereas PET molecular orientation increased remarkably over PTT with increasing draw ratio. Crimp contraction increased sharply at a draw ratio over 2.0, where the crystalline structure of the PET developed sufficiently. A heat set temperature of at least 140 °C was required to develop sufficient crimp contraction. The crystallinity and orientation of the PET was attributed mainly to the crimp contraction of the drawn fiber.

Temperature(oC)

50 100 150 200 250 300

Hea

t flo

w

As-spun fiber1.41.61.82.02.22.5 2.5

2.2

2.0

1.8

1.6

1.4

As-spun fiber

2 θ

0 10 20 30 40

Inte

nsity

(a. u

.)

Fig. 1. DSC thermograms of conjugate fibers for Fig. 2. Equatorial X-ray scattering profiles different draw ratios. of conjugate fibers for different draw ratios.

ACKNOWLEDGEMENT This work was supported by grant No. RTI-0401-04 from the Regional Technology Innovation Program of the Ministry of Knowledge Economy (MKE).

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