JURNAL CHITOSAN

InternationalJournalofTechnology(2010)1:6573ISSN20869614IJTech2010

PREPARATIONANDCHARACTERIZATIONOFCHITOSAN/MONTMORILLONITE(MMT)NANOCOMPOSITESYSTEMS

HeryHaerudin1,AndikaW.Pramono2,DonaSulistiaKusuma1*,AisyiyahJenie1,NicolasH.Voelcker3,ChristopherGibson3

1

ResearchCenterforChemistry,IndonesianInstituteofSciences,

2

KawasanPUSPIPTEK,Serpong,Tangerang15314,IndonesiaResearchCenterforMetallurgy,IndonesianInstituteofSciences,

3

KawasanPUSPIPTEK,Serpong,Tangerang15314,IndonesiaSchoolofChemistry,PhysicsandEarthSciences,FlindersUniversityofSouthAustralia,

GPOBox2100,BedfordPark,SouthAustralia,5042,Australia

(Received:June2010/Revised:June2010/Accepted:July2010)

ABSTRACTAnatural-basednanocompositefilmconsistingofchitosan,montmorillonite(MMT)andcashewnutshellliquid(CNSL)wassynthesized.Thenanocompositewaspreparedbymixingasuspensionofclayparticles(filler,MMT)withasolutioncontainingchitosanasthemacroscopicpolymermatrix.Inthisstudy,itwasproposedthatnon-ioniclong-chainalkylmoleculeswithpossibleinteractionswiththeaminegroupofchitosancouldbeusedasaplasticizer.Asanatu-ralsourceforthesecompounds,anextractofCNSLwasused.Aseriesofchitosan/MMTcom-positesamplescontainingtwodifferentclaycontentsandasamplewithanadditionalCNSLwereprepared.FTIRspectroscopyofthenanocompositefilmsindicatedthat,byadditionofCNSL,amidegroupsofthechitosanareprobablylessattachedandhavemorespaceforvibra-tion.CNSLseemstoprovideintermolecularspacesbetweenthechitosanmolecules.Atomicforcemicroscopy(AFM)analysisshowedthatthecompositecontainedparticlesmeasuring100nmorless,whichconfirmedthatthenanocompositehadbeensuccessfullyproducedbythismethod.AdditionofCNSLasplasticizerimprovedthetensilestrengthby10%andtheelasticmodulusbyalmost18%.Cellgrowthwasobservedonallthenanocompositesamplesstudied.

Keywords:Chitosan;CNSL;Montmorillonite(MMT);Nanocomposite

1.INTRODUCTIONTheuseofbiopolymersascomponentsofcompositesforpackagingmaterialsisaverypopulartopicforcurrentstudies.Studiesregardingtheimprovementofcompositepropertiessuchasbrittleness,lowheatdistortiontemperature,gaspermeability,etc.forawiderangeofapplicationsareverymuchofinterest.Additionally,thedevelopmentofbiobasednanocompositesarecarriedoutwiththeintentionofprovidingphysicalprotectionforfood,improvingfoodintegri-ty,andpreventingcontaminationfrommicrobesandfungi(Rhimetal.,2006).Theuseofbio-basednanocompositesforpackagingmaterialhasbeenreviewed(Akbarietal.,2007).Chitosanasabiopolymerisalsowidelystudiedfordevelopmentofanewcompositematerialwithmontmorillonite(MMT)clay.

*Correspondingauthorsemail:[email protected],Tel.+62217560929,Fax.+62217650549

66PreparationandCharacterizationofChitosan/Montmorillonite(MMT)NanocompositeSystemsVariousexperimentsincludingthemodificationofMMTpropertiesbyconvertingtheMMTintoorgano-montmorillonite(OMMT)priortothenanocompositepreparation(Wangetal.,2008),aswellasthevariationofMMTconcentrationanddimensionstoenhancethepropertiesofthechitosan/MMTcompositewerestudied(Tangetal.,2009).Thoroughstudiesontheinteractionofsmallmoleculessuchasglycerol,asaplasticizer,withchitosaninchitosanfilmwerealsoconducted(Garridoetal.,2007).Regardingthelimitedwater-resistantandmechanicalpropertiesoforiginalbiopolymers,studiesontheimprovementofthosepropertiesbyincludinghydrophobicmaterialintothebiopolymercomposite(Liuetal.,2007),orbytheadditionofothersmallmoleculestoenhancehydrophobicity(Riveroetal.,2009)orplasticity(Suyatma,etal.,2005)werecarriedout.Sinceapplicationofthechitosancompositeasapackagingmaterialforfoodisstronglyconsidered,especiallyduetoitsantimicrobialactivity,moststudiesofthechitosan/claynanocompositehavealsoincludedantimicrobialactivitytesting(Duttaetal.,2009).Itisknownthatthepropertiesofthepolymer/claycompositearestronglyaffectedbytheadditionofsurfactant(s)intothecomposite.Onthosesystems,thetypicalmoleculesarelong-chainalkylquaternaryammoniumchlorides(Xieetal.,2003),whichareeasilyincorporatedintotheclaystructure.Largemoleculeadditions,excepttheuseoflong-chainalkylquaternaryaminesorpolyglycol(Bajdiketal.,2009),tomanipulatethecompositepropertiesareseldomstudied.Inthepresentstudy,itwasproposedthatnon-ioniclong-chainalkylmoleculeswithpossibleinteractionswiththeaminegroupofchitosancouldbeusedasaplasticizer.Asanaturalsourceforthesecompounds,anextractofcashewnutshell(cashewnutshellliquid-CNSL)wasused.Aseriesofchitosan/MMTcompositesamplescontainingtwodifferentclaycontentsandasamplewithanadditionalCNSLwereprepared.CNSLisknownasasourceforcardol,carda-nol,andanacardicacid,andisaphenoliccompoundwithalong-chainalkylgroup.Atypicalsolvent-extractedCNSLcontainsanacardicacid(60-65%),cardol(15-20%),cardanol(10%)andtracesofmethylcardol(Kumaretal.,2002).AdditionofCNSLasasourceofrelativelylargemoleculesintothecompositewasintendedalsotoimprovethehydrophobicityaswellasthemechanicalpropertiesofresultingcomposites.

2.EXPERIMENTAL2.1.MaterialsMontmorillonite(MMT)employedinthisstudywasK10montmorillonitefromSigma-Aldrich.ItiswellknownashavingaCECof70-100meq/100g.ChitosanpurchasedfromSigma-Aldrich(Cat.No.C3646)hadadegreeofdeacetylationof85%minimum.Commercialcetyltrimethylammoniumbromide(CTAB)fromE-Merck(Cat.No.1.02342)wasemployedforthisstudy.CashewNutShellLiquidwasextractedfromcashewnutshellsoriginatingfromSumbaIsland,Indonesia.Priortoitsuseforcompositepreparation,chitosanwaspre-treatedinabasicsolutionof10%NaOH.TheextractionprocedureforCNSLwasasfollows.Freshredistilledn-hexanewasaddedtothecashewnutshellinaroundglassflask.Extractionwascarriedoutbyrefluxing100gcashewnutshellin250mlofn-hexanefor2hours;thisprocedurewasfollowedbyfiltrationandevaporationofn-hexane.

2.2.Preparationofna-montmorillonite(Na-MMT)andorgano-montmorillonite(OMMT)TheOMMTwaspreparedbycationexchangebetweenNa-MMTgalleriesandCTABinanaqueoussolution.MMT(2g)wasdispersedusingastirrerindistilledwatertoobtainclaysuspension,andallowedtostandfor24hoursaftervigorousstirringfor30minutes.CTAB(2g)wasdissolvedindistilledwater,andthendroppedslowlyintotheMMTsuspensionat85Cunderstirring.Afterstirringfor4hours,theproductwaswashedseveraltimeswithdistilled

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waterandfilteredtoensurethecompleteremovalofbromideions,whichweredetectedwithAgNO3untilnoAgBrprecipitatewasfound.Theproductwasdriedat85CtoyieldOMMT.

2.3.Preparationofchitosan/montmorillonitecompositeThechitosansolutionwaspreparedusinga1%aceticacidsolution.4gchitosanwasdissolvedin100mlaceticacidsolution(1%)andstirredfor4hourstoobtainahomogeneousmixture.A2%claysuspensioninaceticacidsolution(1%)wasalsoprepared.Thesuspensionwasaddedintotheresultinggelsuchthata1%and3%MMTcontentinthemixturewasobtained.Themixturewasstirredat50Cfor2daystoobtainahomogeneouschitosan/MMTsuspension.ThisprocedurewascarriedoutusingK10montmorillonite(Sigma-Aldrich),Na-exchangedK10andCTABexchangedK10.ForsamplescontainingCNSL,asolutionof25mgCNSLin100mlethanolwaspreparedseparately.TheCNSLsolutionwasaddedaccordinglyintothechitosan/MMTmixtureafterarigorous2daysofmixing,andthenafinal1%CNSLcontentwasobtained.

2.4.Characterization2.4.1.Infrared(IR)spectroscopyAllIRspectrawereobtainedusingaNicoletAvatar370MCT(ThermoElectronCorporation,USA)equippedwithastandardtransmissionaccessory.SpectraofthecompositefilmswererecordedandanalyzedusingOMNICversion7.0software,intherangeof650-4000cm1ataresolutionof1cm1;thebackgroundwastakenusinganoriginalchitosanpowder.IRofthecompositefilmwasperformedintransmissionmodewithcrushedpowdersinKBrdiscsintherangeof6504000cm1ataresolutionof1cm1.TappingmodeAFMwasperformedonaMultimodeNanoscopeIVmicroscope(VeecoCorporation,USA).CommercialSicantilevers(FESP,VeecoCorporation,USA)wereusedforallexperiments.TheimageswereprocessedandanalyzedusingtheNanoscope5.31r1software(VeecoCorporation,USA).

2.4.2.Differentialscanningcalorimetry(DSC)Inthepresentwork,DSC2920(TAInstruments)wasusedforthemeasurement.Theinstrumentalcellconstantandtemperaturecalibrationwereperformedusingindium.Chitosan/MMTsampleswereanalyzedundercontinuousheatingconditions(10Cmin-1)betweenroomtemperatureand200C.8-100.1mgofsamplewasweighedintoastandardaluminiumpanandplacedontotheDSCcellplatform.

2.4.3.MechanicalpropertiesThemechanicalpropertiesofchitosan/MMTnanocompositesweretestedusingaUniversalTestingMachine,OrientecCo.Ltd.,ModelUCT,5-T.ThespecimenswerepreparedaccordingtoISO527-2.Allspecimensweretestedusingacrossheadspeedof1mm/min.

2.4.4.Cellgrowthtest1cm2membranesweretransferredtowellsofa12wellIwakitissuecultureplate(Cat.No.3815-012).MembraneswereseededwithHEK293cellsatdensity105cells/cm2(3.85x105cellsperwellina2mLvolume)inDMEM(Invitrogen)+10%FCS(JRH)+2mML-glutamine+100U/mLpenicillin100ug/mLstreptomycin(Invitrogen).HEK293cellsweregrowninthepresenceofthemembranesfor20hoursat37C5%CO2.At20hoursmediawasremovedandreplacedwith2ng/mLHoescht33342(Sigma)stainincompletemediaandincubatedat37C5%CO2for0.5hours.Stainingwasvisualizedunderappropriatefluorescentexcitation/emissionconditionsforHoeschtstain.Thephotographsweretakenwitha20xobjectiveonaLeicalaborluxDfluorescentscope.

ClaytypeCNSL68PreparationandCharacterizationofChitosan/Montmorillonite(MMT)NanocompositeSystems

3.RESULTSANDDISCUSSIONTable1asshownbelowliststhesamplesusedforthestudies.Eachsampleconsistsof3%clayoritsmodifiedone.CNSLwasaddedasasolutioninethanol;1%w/wofthechitosanwasusedforfilmpreparation.Table1Listofsamplestestedforthestudies

AdditionK10UntreatedNoK10-CTABOrganicclayNoK10-CNUntreatedYesK10-CTAB-CNOrganicclayYes

Figure1TransmissionFTIRspectraof(a)purechitosan(CS)film;(b)CS/3%K10;(c)CS/3%K10-CN;(d)CS/3%K10-CTAB;and(e)CS/3%K10-CTAB-CNcomposites

Generally,theamidebandsareshiftedtothehigherwavenumberbyadditionoftheCNSL.ByadditionofCNSL,amidegroupsofthechitosanareprobablylessattachedandhavemorespaceforvibration.CNSLseemstoprovideintermolecularspacesbetweenthechitosanmolecules.Thisshouldcreateahigherplasticityintheresultingmaterial.ItshouldbenotedthattheC-Ostretchingbandaround1160cm-1remainedundisturbedbytheadditionofCNSL.

Itshouldbenotedthat,atthepre-processingstage,rawdatasetsarepassedthroughafilterthatgeneratesoutputintheformofmoredatawhichcanbefurtherusedforactualcomparativeanalysisbetweenspecies.ItisevidentfromFigure2thatthedatasetcontainscharactersotherthanpurenucleotidebases.Theseillegalcharactersareremovedbyapplicationofacleansingfilter.Atfirstinstanceitisworthnotingthatanalysisshouldbemadewithoriginaldatavalues;anygarbagecollectionmayleadtodetritionsofresults.

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(a)(b)Figure2MorphologyanalysisoflongitudinalsectionofCS/K10-CTABusingAFM;(a)Particlehorizontalsizeof103nm(b)Particlehorizontalsizeof139nm3.1.InfraredspectroscopyFTIRanalysesofthecompositefilmswereperformedtostudythestructuralchangescausedbymodificationoftheclaycomponentpriortothepreparationofthecomposite.TheIRspectraweretakenbytransmissionaswellastheDRIFTmethod.Thespectrumofchitosanischaracterizedbybroadandintensebandsat3450-3200cm-1(hydrogenbondedOHstretchingoverlappedwithN-Hstretchingbands);C-Hstretchingbandat2783cm-1.TheN-Hdeformationbandofchitosanwasfoundat1559cm-1.Thestrongbandsat1656cm-1and1599cm-1areascribedtotheamideI(C=Ostretching)andamideII(N-Hbendingmodes)ofthechitosan.

3.2.Atomicforcemicroscopy(AFM)AFManalysiswasconductedtodeterminethenanoscalestructureofthecompositesynthesized.AsshowninFigure4,theMMTparticleformingthecompositeischaracterizedbylengthsof103nm(Fig.4a)and139(Fig.4b).However,thesurfaceheightislessthan9.5nm.Thiscanbeexplainedasfollows.TheMMTparticlesformingthecompositeonlyconsistofafewlayers,resultinginMMTparticleswiththicknessesoflessthan10nm.Althoughthelengthoftheparticleismorethan100nm,theformationofparticlesoflessthan10nmindicatesthepresenceofexfoliationfromtheMMTparticles.SincetheMMTareusedasfillers,thenmostlikelythecompositesynthesizedwasintheformoforderedintercalatednanocomposite.

3.3.DifferentialscanningcalorimetryAsshownbythethermogram(Figure3),glasstransitioninDSCwasnotobserved,indicatingthatamorphousstructuredoesnotexist.Nothermosetcuretemperaturewasobservedfrom25to250C.Mostprobablynocrosslinking,formationofnewbondsoccurredinthematerialatthattemperaturerange.DSCthermogramsshowonlythatwaterreleasedfromthefilmatsimilartemperaturerangeasontheoriginalchitosanwhentheformulaofcompositefilmwascontainingCTAB.Itcouldbeexplainedthatthepreparationoforgano-montmorillonite(OMMT)removedmostofthetrappedwatermoleculesfromtheMMT,suchthatlesswaterexistedintheMMTaswellasintheresultingcompositefilm.ItwasexpectedthatthehydrophobicitywouldbeincreasedbytheadditionofCNSL,whichmeans,itwasalsoexpectedthatwatermoleculeswouldbereleasedatamuchlowertemperaturefromthefilmcontainingCNSLintheformulation.

70PreparationandCharacterizationofChitosan/Montmorillonite(MMT)NanocompositeSystems

Figure3DSCthermogramofsamples.Fromabovedownwards:(a)chitosan(CS)powder(C3636,Sigma-Aldrich);(b)CSfilm;(c)CS/3%-K10;(d)CS/3%K10-CTAB;(e)CS/K10-CNand(f)CS/K10-CTAB-CN

ThethermogramsshowthattherewasnoeffectforOMMT,butoncompositescontainingplainunmodifiedMMT(cande),watermoleculeswerereleasedatahighertemperature,andCNSLadditiontotheformulaseemedtoresultinstrongerwaterretentioninthefilm.TheCNSLcomponentmoleculesretainedthetrappedwatermoleculesonmontmorillonite.

Figure4Tensiontestgraphicresults:(a)CS/K10-CTAB(b)CS/K10-CTAB-CN

3.4.MechanicalpropertiesFromthemeasurementsshowninTable2,itisobservablethattheadditionofCNSLincreasesthemoduluselasticity,yieldstrength,tensilestrength,aswellastheruptureofthecomposite.

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Thetensilestrengthisimprovedby10%andtheelasticmodulusbyalmost18%.

Table2Tensiontestresultsfornanocompositesamples

Samplecode

Yieldstrength[Mpa]

Tensilestrength[Mpa]

Rupture[Mpa]

ElasticModulus[Mpa]

CS/K10-CTABavg59.476.975.92470std.dev.1.58.49220

CS/K10-CTAB-CN

avg66.884.684.52910std.dev.3.910.610.7250

3.4.CellgrowthtestItwasdifficulttodifferentiatethelivingcellfromthefilm,sincethechitosanfilmgivesastrongbackgroundfluorescenceusingthisparticularmethod.Despitethisproblem,itcouldbeconcludedthatcellgrowthwasobservedonallthesamplesstudied.

(a)(b)(c)

(d)(e)(f)Figure5Cellgrowthtestonchitosanfilm;(a)CS(Chitosanfilm):++(b)Z3(3%K10-CN):+(c)J3(3%K10-CTAB):Nocells(d)K3(3%K10):+(e)Y3(3%K10-CTAB-CN):+(f)J3(3%K10-CTAB):++

4.CONCLUSIONAnatural-basednanocompositefilmconsistingofmontmorillonite,chitosanandcashewnutshellliquid(CNSL)hasbeensuccessfullysynthesized.IthasbeenproventhatCNSLseemstoprovideintermolecularspacesbetweenthechitosanmolecules.AFManalysisshowedthatthecompositecontainedparticlesmeasuring100nmorless,whichconfirmedthatnanocompositehadbeensuccessfullyproducedbythismethod.Thepreparationoforgano-montmorilloniteremovedmostofthetrappedwatermoleculesfromthemontmorillonite,suchthatlesswaterexistedinthemontmorilloniteaswellasintheresultingcompositefilm,asshownbytheDSC

72PreparationandCharacterizationofChitosan/Montmorillonite(MMT)NanocompositeSystemsanalysis.However,theadditionofCNSLcomponentmoleculesretainedthetrappedwatermoleculesonmontmorillonite.TheadditionofCNSLasaplasticizerimprovedthetensilestrengthby10%andtheelasticmodulusbyalmost18%.Cellgrowthwasobservedonallthenanocompositesamplesstudied.

5.ACKNOWLEDGEMENTThepresentworkwasco-sponsoredbytheEndeavourProgramoftheAustralianGovernmentandwaspresentedatthe11thInternationalConferenceonQualityinResearch.

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