Proceeding ofTd lnternational science postgraduate conference 2014 (ISpczoI4)O Faculf of Science, UniversitiTeknologi Malaysia

GRAFTING OF POLYACRYLOMTRILE ONTO SODIT]M ALGINATEUSING BENZOYL PEROXIDE AS INITIATOR

'AHndgD sAllsu, 2AHMEDY ABU NArM ,*MOHD MARSIN sANAGI4 KHAIRIL JUHANNI ABD KARIM

)'2'3'aDepartment of chemi'*,t".rTil,"lm::Hlfi:ijiliy"ogi Malaysia, 81310 urM

3lbnu Sina Institute for Fundamental Science Studies, UniversitiTeknologi Malaysia, g13l0 UTM

* c orrespondilffitr*fli'iffi3fi:". rs.urm. myI ahmedsdaura@gmail.com, 2ahmedy6kimia.fs.utm.my,3marsin@kimia.

fs.utm. my, a;uhanni@kimia. fs. utm. my

*Corresponding author

Abstract. In this study, grafting of polyacrylonitrile onto sodium alginatewas carried out in aqueous medium using benzoyl peroxide (BPO) as initiator.The graft copolymers were characterized by Fourier tansforms infraredspectroscopy, differential scanning calorimety, thermogravimetric analysis,and scanning electron microscopy. The eff€cts of reaction variables such as theratio of monomer to sodium alginate, amorunt of Bpo, reaction time andteinperature on the percentage grafting G (%) were studied. The optimurnconditions for grafting were achieved at a ratio of sodium alginate toacrylonitrile of 1:3 by weight, 0.1 g of Bpo and reaction temperafure and timeof 80"C and 4 h, respectively. These conditions provided highest percentage ofgrafting and yield of graft copolymerization of 125.s0% and 4t"g4yo,respectively. The results indicate that benzoyl peroxide could be used asthermal initiator for grafting polyacrylonitrile onto sodium alginate

Keywords Grafting, sodium alginate, acrylonitrile, benzoyl peroxide,thermogravimetric analysis

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1.0 il{TRODUCTION

Modificatiol 9f natural polymers (polysaccharides) by grafting vinylrnonomers via radical polyrnerization mechanism has attracted, the interest ofmany scientists[1]. This technique enables the slmthesis of hybrid materials withbroad applications than the unmodified natural polyrners without damaging theinitial properties of the substrate [2,3]. Among polysaccharides, atgin'ate- trasimporlant properties which rendered it a good material of choice foi chemicalmodification because it possesses various functional groups together with uniquephysical properties such as gelling, thickening and-swelliogl th.r" propertiescould be utilized in stabilization of suspensions, emulsions and film formation.Besides, alginate is non-foxic, renewable and biodegradable. Alginic acid oralginate (its salts or its derivatives) as shoum in $ig. 1) is a lineir copolymerconsisting mainly the residue of p-l,4Jinked-D-mannuronic acid (M-Blocki andu-1,4-linked-L-guluronic acid (G-Block) arranged in an irregular blockwisepatfern of varying proportions of GG, MG, and MM blocks[+-ej.nlginic acid isproduced by brown algae species, the relative amounts of M *a c, as weltr astheir sequential arrangement along the polymer chain varies greatly with thesource of the alginate, age of the algae, and the method of extraction [i]. Rtginatehas a broad range of applications in various fields such as in pharmaceuticll forthe controlled release of medicinal drugs[8], biomedical,[3,9] agriculture[lgJ andpurification.[11-13]

L--FJ COONa

M-Block Gli"tock \-____Y-____-_/MG-Block

Figure L:Block pattem of sodium alginate

From the literature survey, chemical modification of alginate by graftingpolyacrylonitrile on its backbone using various redox initiating ryrt"*r [ui" U**oreported U4-L7J, no previous studies have been *uo. oo the graftcopolymerization of acrylonitrile (AN) onto sodium alginate using benToylperoxide (BPO) as thermal initiator.

o-S-.," fu-""*-v"--4""oH cooNa

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2.0 EXPERIMENTAL

z.l Materials

Sodium alginate, benzoyl peroxide and acrylonitrile were from Sigma-Aldrich (Louis,USA), acrylonitrile monomer was distilled under reduced pteJsurbefore used in all the experiments. Dimethylformamide (DMF) and acetone fromQRec (Selangor, Malaysia) were used as received.

2.2 Procedure for graft copolymerization

The grafting reacfions were carried out under nitrogen affirosphere in a 250-mL three-necked flask equipped with a magnetic stirrer, and a nifrogen gas inletsystem, immersed in a constant temperature bath. For each experiment, sodiumalginate solution was prepared by slow addition of weighed amount of sodiumalginate into 200 mL beaker containing distilled water (S0g) and stirred vigorouslyusing a glass rod until a viscous transparent solution was obtained. Then thesolution was transfer into the reaction flask which was immersed into oil bath atreaction temperafure, and then the required amount of BPO dissolved in acetone (5mL) was added slowly to the slurry. After the mixture was stirred fsr 20 min therequired amount acrylonitrile monomer was added. Graft copolyrnerization wascarried out at variots conditions. The gmft copolymerization parameters include;alginate: acrylonitrile ratios 1:3, l:1, 3:l by weight, Bpo content 0.05-0.5 g,reaction time 1-6 h and reaction temperature between (60-90'C). The nitrogenatmosphere and stining were maintained throughout the experiment. After thereaction time was over, the slurry was poured into acetone. The product wasfiltered, dried in vacuum oven at 60oc to constant weight and kept in thedesiccator

2.2.1 Separation of homopolymer

The products were washed using dimethylformamide (DMr) solvent bySoxhlet extraction for removing polyacrylonitrilehomopolynrer. The extractionwas done fot 24 h. After extraction the graft copolymer was dried in a vacuumoven at 60oC to constant weight and kept in the desiccator"

2.2.2 Estimation of grafting parameters

Proceeding of P International Science Postgraduate Conference 2Ot4 {ISrcZU4)@ Faculty of Science, UniversitiTeknologi Mataysia

The graft copolymers were estimated by the following parameters; thepercentage of grafting, G (%) and yield of graft copolymerizatiotL Y (%) fromsquation {l) and (2) respectively [18].

c(%) = ryx1ooY(%) = ryx1oo

(1)

(2)

where ril/r, wo, and w2 denote, respectively, tre weight of the grafted sodiumalginate, the weight of the original sodium alginate and the weight of the monomerused.

2.2.3 Characterization of alginate-g-PAN

Fourier transform infra red spectroscopy (FTIR) was used to confirmed thegrafting reaction. The dried samples were pressed under hydraulic pressure withKBr to forrn transparent discs. The spectra were taken using Perkin Elmerspectrum ru 400 model (usA) and scanned at a frequency t*gi of 4000 - 450cnt

2.2.4 Thermal Analysis

2.2.4.1 Differential scanning Calorimetry

Differential scanning calorirnetry (DSC) analysis was carried out using aThermal Advantage Instrumerrt (Q2000 TA Instruments, usA) using aluminumpan under a 50 ml/min niffogen flow at the heating rate of 20"C/min on thesecond heating of a heating-cooling-heating cycle.

2.2.4.2 Thermogravimetric study

Thermogravimetric (TGA) study of sodium alginate and that of the Alg-g-PAN were carried out with a Thermal Analysis Instnrment (Q500 TA, USA). Thestudy was conducted in an inert amosphere from 50"C to 800oC at a heating rateof 20"C/min.

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225 Scanning electron microscopy analysisThe scanning electron microscopy (sEM) micrographs of pure sodium

ll8lnate and Alg-g-PAN before and after Soxhlet extraction were taken using aJEOL JSM 6390LVSEM (Tokyo, Japan). Before sEM observation, all sampleswere fixed on aluminum stubs and coated with gold using auto fine coater (JFC-1600 model).

3.0 RESULTS AND DISCUS$ON

In order to optimize the reactions conditions for grafting, the amognt ofinitiator, monomer, sodium alginate as well as temperature and time were varied.

3.1 Effect of Sodium Alginate and Acrylonitrile ratioTable 1 represents G (%) and Y {Yo) af various ratios of sodium alginate

and acrylonitrile polyrneized, under various conditions. It was observed that inthe system whereby sodium alginate acrylonihile were varied, both values of G(%) andY (%) show similar effectso in such a way that higher G (%)value showedhigher Y {%\We found that the amouat of sodium alginate and acrylonitrileratios had great effects on percentage grafting G (vr); the system witn nigermonomer concentration was more favorable. The highest acrylonitrile content(3g)gave the highest percentage grafting (l2s.sa%). There.fore as the amouni ofacrylonitrile content increases, the diffirsion of the monomer increases into thesodium alginate backbone this provides more opportunity for graftcopolymerization and consequently percentage grafting increases. this ii inagreement with the results obtained in graft copolymerizatianof acrylonitrile ontoscdium alginate initiated by hydrogen peroxide{l4]. In the ratio sodium alginate:acrylonitrile (3:1), it was observed that both grafting percentage G (%) and]yieldof graft copolymerization Y (o/o) were small values. Because t[e viscosities"of thesystems increased with increase amount of alginate, therefore it is difficult formonomer molecules to diffuse effectively; as a result fewer reactive sites weregenerated.

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3.1.1 Effect of Temperature

The influence of temperature on the grafting was investigated by carryingout th€ reaction at different ternperafures in the range 60-90'C and keeping theother variables constant. In Table 1, the G (%) increased up to 125.5A % attemperature of 80'C then decreased at 90"C. The temperature enhances theactivation of macroradicals as well as diffirsioa of the monomer. It was observsdthat further increase in temperature to 90"C led to a decrease of G (%), which canbe attributed to the increase in the formation of homopolymer as well as prematuretermination of the active sites and increases the contribution of chain transferreaction. Besides, at the reaction temperature of 60oC graft copol)rynerization didnot occur. Although, every polymerization reaction has its own optimum reactiontemperature, similar behavior was observed in the case of grafting itaconic acidonto sodium alginate using BPO as initiatorfl9].

Table 1Effect of polymerization parameters on the percentage grafting, G (7") and Y (%)

Algimte(g) wo

AN (g) TempWz ('C)

W, {e)u c {%)b Y {%)"

3160317031803190

607A t.4780 22590 1.51

r.o:131r.26

3.013.18

3

J

33

1

1

I1

60708090

+ino125.5051,00

3.0031.U}26.00

0.336.m

15.67

41s,417.00

3.0031.0026.40

1.0018.0013.003.13 4.33

Reaction conditions: Time:4 h, water: 80 g and BPO: 0.1 gw0 represents weight of sodium alginateu W, represents weigbt of the copolymer after Soxhlet extractionwz represents weight of acrylonitrileoC (y") represents percentage grafting? ("Al represents percentage yield

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32 Effect of Amount of Benzoyl Peroxide

The effect of amount of benzoyl peroxide (0.05- 0.4 g) on percentagegrafting is shown in Fig. 2. Percentage grafting increases from (0.05- 0.1 g), tltiscould be due to the formation of a greater number of grafting sites as a result ofabstraction of hydrogen atom from the sodium alginate backbone. However,increasing the amount of BPO beyoad 0.1 g resulted in decreased in percentagegrafting due to the increase of termination reactions. Therefore, the optimumamount of BPO for grafting acrylonitrile onto sodium alginate was found to bs 0.1(}b.

r-"--*-'----i t+o -,

120

*t cry.)*#*,J{g6}.

0.2 0.3Amount of BPO {g}

Figure 2: Effect of amount of BPO. Reaction conditions: Alginate: 1 g, AN:3g water: 80 g, reaction time : 4 h,Temp : 80oC

33 Effect of Reaction Time

The reaction time plays a significant role in the graft copolymerizatian.The effect of reaction time was determined in the range (1-6 h) keeping the othervariables constant and the results are shown in Fig.3. It was observed that graftingpercentage G (%) and yield of graft copolymerizatr.on Y (y") increased steadilywith the increase of polymerization time up to 4 h. The highest percentage of

o 100e0980cg60luo40

20

0.1

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Proceeding of2d International Science Postgraduate Conference 2014 (ISPC2014)@ Faculty of Science, UniversitiTeknologi Malaysia

grafting G (%), 125.50% was achieved at that time. Further increase of timebeyond 4 h, both G (%) aod Y (%) began to decrease. This was due to the decreasein monomer concentration and initiator concentration and possibly the reductionof grafting sites on th€ sodium alginate backbone. However, graftcopolymerizalton did not occur at polymerization time of I h.

I

'"+: e{x}*#*: Y(%)

Figure 3: Effect of reaction time.Reaction conditions: Alginat. : 1 g, AN : 3 g,BPO - 0.1 g, water - 80 g, Temp = 80oC

34 Evidence of grafting

3.4.1 IR Spectroscopy

Fig. 4 shows the FT-IR spectra of sodium alginate andAIg-g-PAN. In caseof sodium alginate (Fig.4a).The broad peak at 342lcm-tcorrespond to OH groups,peaks at around 2936,1619, and 1416 cm-r, indicating the stretching vibrations ofaliphatic C- H, COO- (asymmetric), COO- (symmetric), and C- O respectively.Moreover, a nelv absorption band in the spectrum of Alg-g-PAN (Fig. 4b) ataround 2243cmr characteristics of nitrile group appeared which was not f,resent inthe sodium alginate spectrum.

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Figure 4: Infrared specha of sodium alginate (a) and Alg-g-PAN (b)

3.4.2 Thermal Analysis

3.4.2.I Diff,erentiat Scanning CalorimefiyDSC thennogram of pure sodium alginate is displayed in Fig. 5, and no

glass transition temperature (Tg) was observed after heating-cooling-heatingcycle. In case of Alg-g-PAN (Fig 6), TS of polyacrylonitile chains grafted wasfonnd tobe L27"C highs than normal polyacrylonitrile.

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Proceeding oJld International Science Postgradwrte Conf*ence 2014 (ISPC2014)@ Faculty of Science, UniversitiTeknologi Malaysia

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tr! O,OIE'-o*IL,|lrl!o

-os

-{lSfio up

*o=r

-tD! - o.4{:lE-o.'JiEl{.ft!lotE -0.61

I-o.?'l

-o^sl^10fro uF

80 t{X} 12OTempatature {oCl

Figure 5: DSC thermogram ofsodium dginate

t2?sC

ilo 60 s' lOO lto '.40iTemperature ffi

Figure 6: DSC thermogram of Alg-g-PAN

150

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3.4.2.2 Thermogravimetry study

Thennogravimetric analysis (TGA) of sodium alginate is shown in Fig.7. Itwas observed that sodium alginate showed a weight loss in three steps. The initialweight loss of about 14.67% at 5A- 125"C, could be due to evaporation of water ashas been reported by others [20]. The second step (200-250'C) was due todegradation of carboxylate group (coo) which resulted in the loss of coz(decarboxylation) with mass loss of about 37.7A%. Total decomposition ofalginate backbone was observed at the temperature above 400'C.

However, in case of Alg-g-PAN (Fig.8) different thermal behavior wasobserved. The first stage of weight loss of about (18.78%) starts from 200 -250"C, was due to degradation of carboxylate group {COO) to release CO2. Thesecond stage of weight loss (26.33%) started at 320'C -550"C this could be due todegradation of polyacrylonitrile chains grafted. The third stage of weight loss from550 - 800"C was due to decomposition ofsodium alginate backbone- The behaviorof weight loss in decarboxylation process reveals that the graft copolyner hadlower weight loss than sodium alginate, because of potyamylonirile chainsgrafted. This suggests that the therrnal stability of sodium alginate has beenimproved.

Temperature {ocl

Figure 7: TGA thermogram of sodium alginate

s-c 50El.E

3

14.67 S tHrolHoi"tur*1

3I.?0 1[ | co rloecanoxytation)

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Proceeding of2d International science postgradaate conference z0l4 (IspczLl4)O Faculty of Science, UniversitiTeknologi Malaysia

18.t6 !& t torto"**orytation|

Polyacry lor itriledegr8dauon

25.33 en

Algin*. drgrSilioE

Temperature {oC}

Figure 8: TGA thermogram of Alg-g-pAN

35 Scnnning electron microscopy (SEM) analysis

SEM micrographs of the graft copolymer before and after soxhletextraction are shown in Fig 9(a) and 9(b) respectively. It was obvious that thesurface morphology of the graft copolymer had rough surfaceHowever, aftersoxhlet extraction such rough surface disappeared and sponge-like structureappeared due to grafting of polyacrylonifile onto sodium alginate

Figure 9: SEM micrographs of Alg-g-PAN{a) before soxhlet extraction and aftersoxblet extraction (b)

100

G* 80q\

cno3

60

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4.0 CONCLUSIONS

Modification of polysaccharides by graft copolym€rization reactionparticularly employing free radicals to initiate the reactionis an importanttechnique to obtain a chemically modified material with enhanced properties. Thegraft copolymeizatron of polyacrylonitrile onto sodium alginate was carried outusing benzoyl peroxide as initiator. The optimum reaction conditions were foundto be; BPO 0.1 g, (1: 3 by weight) sodium alginate to acrylonitrile ratio, reactiontemperature and time of 80'C and 4 h. Under the optimized conditions thepercentage graftlng G (%) and yield of graft copolymerizationwere 125.50% and4t.84% respectively. The evidence obtained from infrared specfroscopy,thermogravimetric analysis and scanning electron microscopy have proven thegrafting of sodium alginate with polyacrylonitrile. Based on thermogravimetricanalysis result, we found that the stability of sodium alginate has improvedgreatly"

ACKNOWLEDGEMENT

The authors would like to thank UniversitiTeknologi Malaysia for facilitations andthe Ministry of Higher Education Malaysia (MOHE) for financial support throughResearch Grant Vote Number R. J 1 30000.7909.45069.

REI.ERENCES

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T., et al., Preparatinn of Nginic Aci.d and Menr Atginate from Algae and theirComparative Smdy. J. of Polym. and the Envir.,2008. 16(3): p. tSt-ZO+.Ertesvig, H. and s. valla, Biosynthesis and applicatians of alginates. polym. Degrad. andStab., i998.59{1{): p. 85,91.

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Proceeding ofrd International science Postgradaate conferente 2014 (Ispc20t4)O Faculf of Science, UniversitiTeknologi Malaysia

18] Chen, J.-P., et al., Microencapsulation of istett in PEG-amine modified alginate-poly(l-Iysine)-alginate microcapsules fttr constructing bioartificial pancreas. J. of Ferm. andBioengr., 1998.86(2): p. 185-190.

tgl Lee, K.Y. and D.J. Mooney, Alginate: Properties and biomedical applications. progr. inFolym. Sci., 2012. 37(l): p. fi6-126.

tl0] Laq X.2., et al., A novel gelling method for stabilization af phase chnnge materialNa2HPOIL2H2O with sodium alginate grafied sodium acryla,te. Thermochimica Acta,2aA7 . 463(t-2): p" 1 8-20.

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U2l Mishra, D.K., et al., Modification oJ Alginate by gralting of N-vinyl-2-pyrrolidone andstudies of plrysicochemical properties in terms of swetling capacity, metal-ion uptake andfloccalation. Carbohydr Polym, 2010. 80: p. I 147-1154.

tl3] Morsh, Y., et al., Effect of ca2*, Bat*, Sla on alginate microbeads. Biomacromol, 2006.7: p. 1471-80.

[14] y6rrng-Hee Lee, J.-S. Kirn, and H.-D. Kina, A Study of Biottegradable SaperabsorbentMaterials Based on Acrylonitrile Grafied Sodium Alginate. Key engr maw, 2005. 277-279: p.450454.

[5] shah, s.8., c.P. Patel, and H.c. Trivedi, Fenton's reogent-tnitiated graftcopolymerization of acrylonitrile onto sodiwn alginate. J Appl Polym Sci, 1994. 5L(8): p.t42t-1426.

ll6l Zohuriaan-Mehr, M.J. and A. Pourjavadi, New polysaccharide-g-polyacrytonitrilecopolymers: synthesis and thermal charocterization. Polym. Adv. Technol.,2A16. M(7):p.508-516.

[17] Radhahishna N.o et al.o Sadies on thc gra{t copolymerizstion af acrylonitrile antasodium alginate. JMS-PURE AppL. CIIEM., A lgg4. 3l: p. 5g1_5g1.

U8] Kaefiatip, K. and V. Tanrattanatul , Preparation of cassava starch grafted withpolysryrene by suspension polymerization carbohydr polym, 200g. 73(a): p. 647-6ss.

[19] Nwan, tr., K. Fatma, and tr. Murat, Graft copolymerization of itaconic acid onto sodiamalginat e us in b e nzoy I p e roxide . Carbohydr Polyrn, 20 I 0. 7 9 : p. 665 -67 2.

I20l Laurienzo, P., et al., Novel alginate--atrylic polymers as a platform for drug delivery.Joumal of Biomedical Materials Research paxr A, 2006. TSA(3); p. 523-531.

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