1

Fouad Aliev

Relaxation ofLibrational Mode inConfined LiquidCrystalintroduction

Dielectric spectroscopy can beapplied to investigate multipleaspects of the influence of confine-ment on dynamic properties of liquidcrystals impregnating porousmatrices. Applications of dielectricspectroscopy for investigations ofconfined liquid crystals [1-7]revealed new information on thechanges in the molecular mobility aswell as changes in the phasetransition temperatures as a result ofthe influence of the confinement.Alkylcyanobiphenyls such as4-n-octyl-4’-cyanobiphenyl (8CB)are liquid crystals, which have beendeeply investigated in the past andwhose dielectric bulk properties havebeen quite clearly understood. Theirmolecules have a large dipolemoment (~5 D) oriented along themolecular long axis, which signify-cantly simplifies the understandingof the dielectric behaviour. In thenematic phase in a geometry inwhich the probing electric field E isparallel to the director the relaxationdue to the restricted rotation of themolecules about their short axis isdetected. The temperature dependenceof the corresponding relaxation timesobeys empirical Arrhenius equation.

For the geometry in which theelectric field E is perpendicular tothe director n, the relaxation due tolibrational motion of the moleculesshould be observed. This process hascharacteristic frequencies about 10times higher than the relaxation dueto the molecular rotation. Theavailable information on dynamics oflibrational mode even for bulk liquidcrystals, to our knowledge, is scarce,because in order to obtain anappropriate orientation of moleculeswith respect to probing electric fieldthe sample should be placed intomagnetic field. This is very difficultbecause the samples cells used formeasurements at very highfrequencies (hundreds of Megahertz)are large and do not fit betweenpoles of conventional magnetsproviding magnetic field sufficientfor required molecular orientation.

liquid crystal confinementTo obtain quantitative description

of the librational mode, we apply

dielectric spectroscopy to investigaterelaxation properties of 8CBconfined in 200 nm cylindrical pores

Dielectrics Newsletter Scientific newsletter for dielectric spectroscopy Issue february 2005

F req ue nc y [H z]

10 5 10 6 10 7 10 8 10 9 10 10

ε εεε '' m

0 .0

0 .1

0 .2

0 .3

0 .4

0 .5 ro ta tio n

lib ra tio n

Fig. 1: Comparison of dielectric spectra of rotational (closed circles) andlibrational (opened circles) modes of 8CB confined in 200 nm cylindrical. Allmeasurements taken at T = 310K.

Frequency [H z]106 107 108 109 1010

ε εεε ''

0.03

0.06

0.09

0.12

300.15K291.15K281.15K273.15K

ε εεε ''

0.08

0.16

0.24

0.32 325.15K321.15K317.15K313.65K

ε εεε ''

0.05

0.10

0.15

0.20313.05K312.85K310.15K305.15K

a

b

c

Isotrop ic

N em atic

Fig. 2: Frequency dependence of the imaginary part of the dielectric permittivityof 8CB confined in 200 nm cylindrical lecithin treated pores (radial orientationof molecules) at different temperatures.

february 2005 Dielectrics Newsletter

2

of Anopore membranes treated withlecithin. This treatment provideshomeotropic boundary conditions(the molecules are orientedperpendicularly to the pore walls) forconfined 8CB. Since the pore axis isparallel to the probing electric fieldand the molecular dipole moment isoriented perpendicularly to itsdirection, such a configurationmakes it possible to investigate thedynamics of librational (tumbling)mode by dielectric method. Inuntreated pores the orientation ofmolecules is axial (the molecules areoriented in parallel to the pore axis)and the mode due to reorientation ofmolecules around short axis isdetected. Therefore relaxations dueto both mechanisms can beinvestigated separately in thesepores. We used NOVOCONTROLequipment to perform theseexperiments.relaxation processes

Figure 1 illustrates the differencein relaxation due to reorientation ofmolecules around short axis and dueto their librational motion, observedin 8CB confined in cylindrical poreswith axial (parallel to the probingelectric field) and radial(perpendicular to the electric field)orientations. It is clear that therelaxation process in lecithin treatedmatrices (radial orientation) isobserved at much higher frequenciesthan in the bulk sample andtherefore, cannot be assigned to thesame mechanism.

Since the molecules of 8CB do not

have any component of dipolemoment perpendicular to the longaxis, the only explanation to theobserved high frequency relaxationin the treated sample is to associate itwith librational motion of molecules.temperature dependence

The temperature dependence ofdielectric spectra of the librationmode is complicated and verydifferent from the behavior of thereorientation mode. Figure 2 showsthree types of temperature depend-ences of the dielectric spectraobserved for confined 8CB (withradial boundary conditions inanisotropic phases) in three ranges.In the temperature ranges corres-ponding to the bulk isotropicphase (a) and Sm-A and supercooledstate (c), the positions of ε''m move tolower frequencies with decreasingtemperature.

The spectra for isotropic phase inthis sample are due to the reorien-tation of molecules around theirshort axis, since there is no directorin this phase and orientations ofmolecules in this phase are random.Therefore the temperaturedependence of these spectra as wellas the temperature dependence of thecorresponding relaxation times -isotropic phase are typical for theisotropic phase of liquid crystals. Innematic phase (Fig. 2, b), thepositions of ε''m move to higherfrequencies with decreasingtemperature, indicating the fasterrelaxation rate at lower temperatures.

relaxation times of rotationand libration processes

The temperature dependence of therelaxation times (libration mode)obtained for 8CB confined in lecithintreated cylindrical pores is illustratedin Fig. 3.

The temperature dependence ofrelaxation times of this mode istotally different from the behaviourobserved in investigations ofrelaxation due to reorientation ofmolecules around their short axis(see Fig 3). The relaxation time oflibrational mode in the temperaturerange corresponding to the nematicphase increases upon increasing thetemperature towards the nematic-isotropic transition temperature. Incontrast, the temperature dependenceof the relaxation times of the processdue to reorientation of moleculesaround the short axis decreases uponincreasing the temperature in thesame temperature range. Theinterpretation of the results obtainedin nematic phase needs theinvolvement of the temperaturedependence of the orientational orderparameter. The decrease ofrelaxation time in the temperaturerange corresponding to the nematicphase of 8CB could be due to anacceleration of the process withincreasing the order parameter.In the sample with homeotropic(radial) boundary conditions, in thecase of perfect order and taking intoaccount that the dipole moment ofthe molecule is parallel to its longaxis, the projection of the dipolemoment on the direction of theelectric field, which is along the poreaxis, is minimal because thefluctuations of the molecularorientations with respect to the radialdirection are very small. Thesefluctuations of the dipole moment (ormolecular long axis) correspond tothe librational motion of themolecule and the amplitude of thefluctuations determines therelaxation rate of the dipole in theviscous media. At highertemperatures, these deviations(fluctuations) are of greateramplitude (the order parameter issmaller) and this requires longer timeto complete one librational cycle. Asa result, the relaxation rate is smallerfor fluctuations of greater amplitudeand vice versa. Such behaviour hasresulted in the particular temperaturedependence of relaxation timesobserved for the librational mode inthe nematic phase temperature range.In the smectic-A phase andsupercooled state, the temperaturedependence of relaxation times is

1000 / T [K-1]3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7

ln ( τ τττ

[ [[[s]) ])])])

-21

-20

-19

-18

-17

-16

Is N Sm-A

Supercooled

rotation

libration

Fig. 3: Temperature dependences of relaxation times of the processes due toreorientation of molecules around their short axis (closed circles) and ofrelaxation times of the librational mode (opened circles) in confined 8CB. Inisotropic phase the relaxation times correspond to the process due to the rotationof molecules around their short axis for both graphs.

february 2005 Dielectrics Newsletter

3

mainly determined by the variationsof viscosity.

The dynamics of the librationalmode is totally different from thebehaviour observed in investigationsof relaxation due to reorientation ofmolecules around their short axis.

The interpretation of thetemperature dependence ofrelaxation time needs theinvolvement of the temperaturedependence of orientational orderparameter and suggests that thebetter orientational order the fasterthe process due to libration ofmolecules.

References[1] F. M. Aliev and M. N. Breganov,Sov. Phys. JETP. 68, 70 (1989).[2] S.R. Rozanski, R. Stanarius, H.Groothues, and F. Kremer, Liq.Cryst. 20, 59 (1996).[3] G.P. Sinha and F.M. Aliev, Mol.Cryst. Liq. Cryst. 304, 309 (1997).[4] Cramer, Th. Cramer, F. Kremer,and R. Stannarius, J. Chem. Phys.106, 3730 (1997).[5] G.P. Sinha and F.M. Aliev, Phys.Rev. E 58, 2001 (1998).[6] S. Frunza, L. Frunza and A.Schlonhals, J. Phys. IV France 10,Pr7-115 (2000).[7] F. Aliev, Z. Nazario, G. Sinha,Journal of Non-Crystalline, v. 305,218 (2002).

Prof. Fouad AlievUniversity of Puerto Rico, San Juan,PR 00931, USAfaliev@rrpac.upr.clu.edu

Holger Neurohr, Wulff Possart

Amine Cured EpoxyLayers on Metals –Network DynamicsDuring Thermal andHygrothermal Ageingintroduction

The broad application of adhesivejoints and polymer layers inengineering is always coupled withthe topic of durability. Under-standing of the fundamental ageingmechanisms and their influence onadhesion and molecular structure inpolymer metal bonds is essential forthe improvement of durability.

Due to its sensitivity to rotations ofpermanent dipoles in the electricfield, dielectric spectroscopy (DES)offers the possibility to characterisemolecular dynamics in polymersover a large frequency range.

In this paper the changes ofnetwork dynamics are reported foran amine-cured epoxy adhesive onmetals during thermal andhygrothermal ageing. Themodification of macromoleculardynamics is studied by DES over aperiod of 100 days of exposure.experimental details

The metal substrates are preparedby physical vapour deposition ofpure Al or Cu on silicon wafers. Theresulting metal surfaces are coveredby their native oxides and by theusual adsorption layer from ambientcarbonaceous contaminants. Theadhesive regarded in this paper

consists of diglycidylether ofbisphenol A (DGEBA) as the epoxyresin and diethylene triamine(DETA) as the curing agent (100 : 14by weight).

Resin and hardener are thoroughlymixed in the molten state at 55 °C(melting point of DGEBA: 42 °C)for 5 min in a closed glass vessel.During rapid cooling down to roomtemperature within about 1 min,further stirring is performed.

Epoxy layers of 5 µm or 25 µmthickness (dEP) are prepared bycasting the reactive mixture on thesubstrates. Curing proceeds at roomtemperature for 48 h followed by a1 h post-curing step at 120 °C in dry,CO2-reduced atmosphere (dew point:-70 °C, CO2 content: < 200 ppm).Then, the samples are stored at 40 °Ceither in argon or in regular moist air(90 % r.h.) for up to 100 d. Atselected ageing times, samples weretaken from the ageing vessel, driedin vacuum and evaporated with an Alcounter electrode (∅ = 5 mm). Themodification of theirmacromolecular dynamics was stud-ied by dielectric broadbandmeasurements in a frequency rangeof 10-2 Hz to 106 Hz carried out witha NOVOCONTROL High ResolutionDielectric Alpha Analyser.

In the first step, the ageing effectson the local dynamics (sub-Tg-relaxation) in the epoxy layers wereanalysed by isothermal frequencyscans in the range from -80 °C to+40 °C (∆T = 5 K) – see Fig. 1 foran example. Afterwards, the

10-2 10-1 100 101 102 103 104 105 106

0,017

0,0220,0280,033

0,056

0,111

0,167

0,2220,278 -100 °C

-80 °C -60 °C -40 °C -20 °C 0 °C +20 °C +40 °C +60 °C

ε ´́

f [Hz]Fig. 1: Dielectric loss spectra ε″(f, T) for a 25 µm epoxy onAl prior to ageing. Only the secondary relaxation process ispresent. For T > 30 °C the high frequency wing of the α-relaxation appears.

0,0033 0,0036 0,0039 0,0042 0,0045 0,004810-7

10-6

10-5

10-4

10-3

10-2

10-1

100

64

68

72

76

80

84

88

05 µm epoxy on Al 25 µm epoxy on Al 05 µm epoxy on Cu 25 µm epoxy on Cu

τ max

[s]

1 / T [K-1]

40 20 0 -20 -40 -60 T [°C]

Ea

[kJ/m

ol]

Fig. 2: Arrhenius plot –log τ vs. 1/T for epoxy layers on metalsprior to ageing. In the inset the activation energy Ea, given by thelinear fits, demonstrate the increased activation energies in the 5µm epoxy layers.

february 2005 Dielectrics Newsletter

4

influence of ageing on the glasstransition (α-relaxation) wasinvestigated by experiments at fixedfrequencies and continuouslyincreasing temperature (from -10 °Cto +200 °C, with β = 8 K/min).results and discussion

In the glassy state, the dielectricproperties of the epoxy layers aredominated by the local motions ofmolecular dipoles in the network (cf.the peaks in Fig. 1). A decrease oftemperature results in a more andmore constrained network dynamicswhich reduces the local motions. Ameasure for the energy to activatethese processes is given by theapparent activation energy Ea givenby the Arrhenius equation whichdescribes the relaxation time of thesecondary relaxation as a function of

temperature: max

aERTexp

β β

∞τ = τ .

The Relaxation timemax max1 2 fτ = π for the maximum fmax

of the secondary relaxation peak

in ε’’(f) is obtained by fitting by aHavriliak-Negami function [1,2].

The Arrhenius plot (Fig. 2)provides straight lines for τmax(1/T)thus classifying the observed processas a secondary relaxation. Prior toageing, the local dynamics arecharacterised by increased activationenergies in the 5 µm epoxy layers ascompared to the 25 µm layers (insetof Fig. 2). For both dEP-values, themean activation energies on Cu tendto be somewhat higher than on Al.Thus, the local dynamics of the non-aged state depends on epoxythickness and slightly on substratematerial.

During hygrothermal ageing, twosignificant changes are observed inthe spectra of the epoxy layers(cf. ε’’(ω)|T = –30 °C in Fig. 3 asexample). During the first four days,the secondary relaxation peakreduces its width which correspondsto a narrowing of the relaxation timedistribution for the local mobility.

This effect is obvious on bothsubstrates for both dEP-values.

In the course of further ageing, therelaxation peak shifts in position. Forall 25 µm layers and for the 5 µmlayers on Al, the relaxation peakshifts to higher frequencies whereasthe peak in the 5 µm layers on Cutends to shift to lower frequencies.

During thermal ageing (e.g.Fig. 4), the width of the relaxationtime distribution also reduces signifi-cantly within the first four days. Butin the further course of ageing therelaxation peak is stable in positionand width in contrast to hygro-thermal ageing.

Accordingly, both thermal andhygrothermal ageing reduce thewidth of relaxation time distributionswithin the first days. In addition,hygrothermal ageing affects theaverage local network dynamics. Thechanges are specific for the substratematerial and depend on the layerthickness dEP.

10-2 10-1 100 101 102 103 104 105 1060,05

0,100,10

0,15

0,200,20

0,25

0,300,30

0,35

0,400,40

0,45

0,500,50

0,55

0,600,60T = -30 °C

0 d 4 d 25 d 45 d 64 d 102 d

log ε

´´

f [Hz]

10-2 10-1 100 101 102 103 104 105 1060,35

0,400,40

0,45

0,500,50

0,55

0,600,60

0,65

0,700,70

0,75

0,800,80

0,85

0,900,90

0,95

0 d 4 d 16 d 36 d 64 d 101 d

log ε ´́

f [Hz]

T = -30 °C

10-2 10-1 100 101 102 103 104 105 1060.20

0.30

0.40

0.50

0.60

0.70

0.80

T = -30 °C

0 d 4 d 9 d 36 d 64 d 102 d

log

ε ´´

f [Hz]10-2 10-1 100 101 102 103 104 105 106

0,200,20

0,30

0,400,40

0,50

0,600,60

0,70

0,800,80

0 d 9 d 16 d 64 d 101 d

log ε

´́

f [Hz]

T = -30 °C

Fig. 3: Dielectric loss spectra ε’’(f) during hygrothermal ageing at T = –30 °C of aa) 25 µm epoxy on Al, b) 25 µm epoxy on Cu, c) 5 µm epoxy on Al and d) 5 µm epoxy on Cu.

a) b)

c)

d)

february 2005 Dielectrics Newsletter

5

The cooperative macromolecularmobility of the α-relaxation in theepoxy layers is considered bydielectric measurements with a

constant heating rate β at a numberof fixed frequencies. For the non-aged state, these temperature scansshow the dynamic glass transition for

the epoxy matrix in the range of130 °C – 160 °C at 100 Hz (seeFig. 5). As indicated by the strongincrease of the permittivity ε’ above

10-2 10-1 100 101 102 103 104 105 1060,5

0,6

0,7

0,8

0,9

1,0

1,1

1,2

0 d 4 d 16 d 36 d 64 d 81 d 102 d

log ε

´´

f [Hz]

T =-30 °C

10-2 10-1 100 101 102 103 104 105 1060.40.4

0.5

0.60.6

0.7

0.80.8

0.9

0 d 4 d 16 d 36 d 64 d 103 d

log ε

´́

f [Hz]

T = -30 °C

10-2 10-1 100 101 102 103 104 105 1060.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 d 4 d 16 d 36 d 64 d 102 d

log

ε ´´

f [Hz]

T = -30 °C

10-2 10-1 100 101 102 103 104 105 1060.2

0.3

0.4

0.5

0.6

0.7

0 d 4 d 16 d 36 d 64 d 102 d

log ε

´´

f [Hz]

T = -30 °C

Fig. 4: Dielectric loss spectra ε’’(f) during thermal ageing at T = –30 °C of aa) 25 µm epoxy on Al, b) 25 µm epoxy on Cu, c) 5 µm epoxy on Al and d) 5 µm epoxy on Cu.

0 20 40 60 80 100 120 140 160 1800,5

0,6

0,7

0,8

0,9

1,0

05 µm epoxy on Al 25 µm epoxy on Al 05 µm epoxy on Cu 25 µm epoxy on Cu

100 Hz, 8 K/min

log ε

´

T [°C]

glass transition

Fig. 5: Primary glass transition in the epoxy layers on metalsprior to aging.

20 30 40 50 60 70 80 90 100 1102,75

3,00

3,25

3,50

0 d 4 d 16 d 36 d 64 d 101 d

100 Hz, 8 K/min

ε εεε ´

T [°C]

2nd glass transition

Fig. 6: Second glass transition during hygrothermal ageing for25 µm epoxy on Cu.

a) b)

c)

d)

february 2005 Dielectrics Newsletter

6

+150 °C, the epoxy layers on copperare stronger affected by electrodepolarisation. During hygrothermaland thermal ageing as well, a secondglass transition Tg,2 emerges withinfour days of ageing, well below thematrix glass transition (see Fig. 6 forexample ).

It indicates that a new, moremobile phase separated inside theepoxy matrix.

The effects of ongoing ageing onthe two glass transitions are quitecomplex. During the 100 days ofhygrothermal ageing, the Tg of thematrix glass transition goes througha maximum (see Fig. 7) which ismore obvious on Cu than on Al.Moreover, the maximum on Cu ismore pronounced for the thinnerepoxy layers. For the 25 µm epoxyon Al, the Tg increases almostmonotonously. All that indicates asuperposition of several processesinduced by ageing.

During thermal ageing (Fig. 8)only the Tg of the 5 µm epoxy layerson Al tends to rise by 4 K. Tg of theother samples seems to be notaffected by thermal ageing over aperiod of 100 days.

The behaviour of Tg,2 is veryspecific for the two dEP-values andfor the metal substrates (Fig. 9). Forthe 5 µm layers on Al and Cu, Tg,2increases with different rate by ~3 Kduring hygrothermal ageing. In the25 µm layers, Tg,2 is not clearlyaffected on Cu whereas Tg,2 goesthrough a maximum on Al anddecreases to a value 4 K below theinitial Tg,2.

In contrast, thermal ageingstimulates a remarkable increase ofTg,2 in all epoxy layers (Fig. 10). Theeffect is more pronounced in the5 µm layers.conclusion

Thermal and hygrothermal ageingover 100 days lead to obviouschanges of the network dynamics inthe epoxy layers studied in this work.These changes result frommodifications of the epoxy that arenot only specific for the ageingconditions but also depend on thesubstrate material. Furthermore,these aging effects are more intensein thinner epoxy layers. Surprisingly,the substrate affects the epoxy oversuch great distances as 5 µm.

The chosen ageing conditions are

relatively mild and proceed in theglassy state of the epoxy.Nevertheless, they produce a newglass transition well below theprimary glass transition of the epoxymatrix. This indicates the separationof a second phase with increasedcooperative mobility. Both glasstransitions are affected in specificways by ageing.

Further investigations are inprogress in order to understandwhich mechanisms are activatedduring ageing and how they affectthe chemical structure and themorphology of the epoxy layers.

References[1] S. Havriliak and S. J. Havriliak,Dielectric and Mechanical Relaxationin Materials: Analysis, Interpretation,and Application to Polymers; Hanser-Verlag, (1997).[2] F. Kremer and A. Schönhals,Broadband Dielectric Spectroscopy,Springer-Verlag, (2002).

Holger Neurohr, Prof. Wulff PossartSaarland UniversityP.O.B. 151150D-66041 Saarbrueckenw.possart@mx.uni-saarland.de

0 10 20 30 40 50 60 70 80 90 100

134

136

138

140

142

144

146

148 05 µm epoxy on Al25 µm epoxy on Al05 µm epoxy on Cu25 µm epoxy on Cu

T g[°C

]

ageing time [d]0 10 20 30 40 50 60 70 80 90 100

132

133

134

135

136

137

138

139

140 05 µm epoxy on Al25 µm epoxy on Al05 µm epoxy on Cu25 µm epoxy on Cu

T g[°C

]

ageing time [d]Fig. 7: Matrix glass transition Tg during hygrothermal ageing forepoxy layers on metals.

Fig. 8: Matrix glass transition Tg during thermal ageingfor epoxy layers on metals.

0 10 20 30 40 50 60 70 80 90 100

48

50

52

54

56

58

05 µmepoxy on Al25 µmepoxy on Al05 µmepoxy on Cu25 µmepoxy on Cu

T g,2

[°C]

ageing time [d] 0 10 20 30 40 50 60 70 80 90 10048515457606366697275788184

05 µm epoxy on Al25 µm epoxy on Al05 µm epoxy on Cu25 µm epoxy on Cu

T g,2

[°C]

ageing time [d]Fig. 9: Second glass transition Tg,2 during hygrothermal ageing forepoxy layers on metals.

Fig. 10: Second glass transition Tg,2 during thermal ageingfor epoxy layers on metals.

february 2005 Dielectrics Newsletter

7

Graham Williams

Broadband DielectricSpectroscopy and itsApplication 2004 inDelft

The 3rd International Conferenceon Dielectric Spectroscopy and itsApplications was held at DelftUniversity of Technology on 23-26August 2004. Organised by Prof.Michael Wübbenhorst and his teamat the TU-Delft, the conferencefollowed the tradition of earlier DRPMeetings held at Jerusalem andLeipzig.

It was attended by over 160scientists from 30 countries; 65lectures were given and 105 Posterspresented, describing currentresearches using broadbanddielectric spectroscopy (BDS). Thelarge attendance included a highproportion of young scientists. Newresearches and active discussionsbetween participants demonstratedthe welcome resurgenceinternationally of dielectrics science.

The Meeting was supportedfinancially by the TU Delft, DCM-TU Delft, KNAW, FOM and DSMin the Netherlands and NovocontrolTechnologies.

The variety of topics in the invitedtalks was exceptional, ranging fromthe very fundamental (e.g. Kramers-Kronig relations by van Turnhout) toapplications of BDS to complexsystems (e.g. of treated blood serumby Gorobchenko et al).As in the previous Conferencesmany presentations described thestructural and secondary relaxationsin amorphous polymers and glass-forming liquids, as measured overlarge frequency/temperature ranges(Böhmer, Frick, Richert, Nozaki,Alegria, Yagihara, Capaccioli,Massalska-Arodz, Vassilikou-Dova,Stevenson) together with studies ofpressure/temperature effects (Roland,

Casalini, Floudas). Theoreticalmodels were proposed for multipleprocesses in amorphous systems(Diezemann, Dyre, Halpern, Eker).

BDS studies were described forpolymer blends/mixtures (Ngai),liquid mixtures (Blochowicz), water-containing systems (Feldman,Lyashchenko, Swenson, Vassilikou-Dova, Devautour-Vinot, Grineva,Grigera, Hernandez-Perni, Caduff),biological systems (Gatash, Stapert,Sekine), ferroelectric materials(Furukawa, Gerhard-Multhaupt,Bauer, Pawlaczyk, Fichtl, Ben Ishai),liquid crystals (Kresse, Sinha, Aliev,Dantras) and nano/meso-structures(Stevens) together with real-timeBDS studies of crystallization(Ezquerra, Wurm), bulkpolymerization (Johari) and physicalaging (Fukao, Wypych). AC ion-conductivity studies of solids werealso described (Leon, Runt,Kranbuehl, McLachlan). A tribute tothe late Prof. Dan Kivelson wasgiven by the writer.

Newer topics included nanoscaleand non-linear conductivityspectroscopy in inorganic solids(Roling), BDS studies of moleculardynamics in ultra-thin layers and inconfined environments (Kremer,Wübbenhorst, Fukao, Schönhals,Serghei), molecular dynamicssimulations of isotropic and orientedpolystyrene (Lyulin), non-resonanthole-burning of glass-formingliquids (Blochowicz) and non-lineardielectric resonance spectroscopy ofnew cellular (foamed) ferroelectretpolymers (Bauer, Gerhard-Multhaupt).

The large number of posterscomplemented the above talks,especially BDS studies of nano-confined films, of amorphouspolymers, functional organic andinorganic materials (egferroelectrics), biological systems(blood serum, frog-muscle, bonecollagen), conduction phenomena in

organic polymers and inorganicsolids, while new techniques wereintroduced (dielectric depth-profilingin epoxy coatings, temperature-modulated dielectric analysis forcure-monitoring).

In the Measurement Forum DrSchaumburg gave a presentation ofthe NOVOCONTROL range ofequipment.

Few talks and posters wereconcerned with the theory ofdielectric relaxation and conductionof simple and complex materials.This appears to be one area thatneeds more input to aid ourunderstandings of the dielectricphenomena presented at this Meeting.

On the Tuesday evening Confereesenjoyed a Boat Excursion (with bandand dancing) around the port ofRotterdam, during which theConference Dinner was served,while on the Wednesday eveningthey were treated to superb soloperformances by Profs. Kremer,Wübbenhorst and Gerhard-Multhaupt at a special ChamberConcert Scientists for Scientists heldat the TU Muziekcentrum.

The organisation of BDS 2004 wasexcellent in every way. We thankProf. Wübbenhorst and his team (PJDroppert, VR Lupascu, P vanMourik, J van Turnhout and TVerheul-Mentink) for all they didbefore and during the Meeting tomake this such a successful andmemorable Meeting in the beautifulold city of Delft.Further details can be seen athttp://www.polymers.tudelft.nl/ids2004/index.html

Prof G Williams, Department ofChemistry, University of WalesSwansea, SWANSEA SA2 8PP, UKg.d.williams@keele.ac.uk

Dielectrics Newsletter february 2005

8

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TaiwanJIEHAN Technology CorporationNo. 58, Chung Tai East Road, 404Taichung / TaiwanPhone ++886-4-2208-2450Fax: ++886-4-2208-0010Mail jiehantw@ms76.hinet.netContact: Mr. Peter Chen

Middle EastNational Scientific Company Ltd.P.O.Box 437Riyadh 11411 K.S.A.Phone +966 1 473 6284Fax +966 1 473 7759Mail nsc@digi.net.saContact: Mr. Osama Ali

Editor Dielectrics Newsletter: Gerhard Schaumburg. Abstracts and papers are always welcome. Please send your script to the editor

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BDS 10

BDS 20

BDS 40

BDS 50

BDS 70

BDS 80

1 m

Hz

10-3

10 m

Hz

10-2

100

mH

z10

-1

1 H

z10

0

10 H

z10

1

100

Hz

102

1 kH

z10

3

10 k

Hz

104

100

kHz

105

1 M

Hz

106

10 M

Hz

107

100

MH

z10

8

1 G

Hz

109

10 G

Hz

1010

100

µHz

10-4

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10 µ

Hz

10-5