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1、TEMPERATUREChineseJournalofPolymerScienceVo1.24.No.2.2O06).195-203ChineseJournalofeolymerScience2006WorldScientificTEMPERATUREANDpHRESPONSE.ANDSWELLINGBEHAVIoROFPOROUSACRYLoNITRILE.ACRYLICACIDCoPoLYMERHYDRoGELSJianHuang,ZhimingHuang,YongzhongBaoandZhixueWengStateKeyLaboratoryofPolymerReactionEnginee
2、ring,ZhejiangUniversity,Hangzhou310027,ChinaAbstractMacroporousacrylonitrileacrylicacid(ANAA1copolymerhydrogelsweresynthesizedbyfreeradicalsolutionpolymerizations,usingammoniumpersulfate(APS)/N,N,:te仃amethylethylenediamine(TEMED1redoxinitiatorsystemandalcoholsporogens.Themorphology,temperatureandpHs
3、ensitiveswellingbehavior,andswellingkineticsoftheresultinghydrogelswereinvestigated.Itwasfoundthatalcoholtypeandconcentrationhadgreatinfluencesontheporestructureandporosityofhydrogels.Theporesizeofhydrogelincreaseswiththemoderateincreaseofthelengthofalcoholalkylchain.However,afurtherincreaseofall(yl
4、lengthwouldresultintheformationofcauliflower-likestructureandthedecreaseofporesize.Theporosityofhydrogelsincreaseswiththeincreaseofporogenconcentrationinthepolymerizationmedium.ThehydrogelswithmacroporousstructureswellorshrinkmuchfasterinresponsetothechangeofpHincomparisonwiththeconventionaIhydrogel
5、withoutmacroporousstructure.Furthermore,theresponserateiscloselyrelatedtotheporosityofthehydrogels,whichcouldbeeasilycontrolledbymodulatingtheconcentrationoftheporogeninthemedium.Thecircularswellingbehaviorofhydrogelsindicatedtheformationofarelaxingthreedimensionalnetwork.Keywords:Acrylonitrile;Acry
6、licacid;Poroushydrogel;SwellingbehaviorINTRoDUCTIoNHydrogelsarecrosslinkedandhydrophilicthreedimensionalpolymernetworks,containingswellingwaterorotherbiologicalfluid.Stimulisensitivehydrogelsundergodramaticvolumechangesinresponsetoexternalstimuli,suchassmallchangesintemperature,pH,lightandothers【.Du
7、etotheirspecialproperties,hydrogelshavegainedmoreandmoreinterestinseveralapplicationfields.suchasmaterialsforimmobilizationofbiomolecules.drugdeliverysystemsandsoon4,5J.However,thesuccessfulapplicationofhydrogelsisalwayslimitedbytheirlowresponserate引.Thisproblemcanbepartiallyovercomebyreducingthesiz
8、eofgelsamplestoshortenthediffusiondistance.Recently.itwasfoundthattheinoductionofporosityintohydrogelwasaneffectivewaytoimprovetheresponserate,becausetheporousstructurefacilitatesthediffusionofwaterthroughthelargesurfaceareaintothepores.So,manyresearchershaveattemptedtoprepareporoushydrogelsinordert
9、oireprovetheirresponserate.Wueta1.preparedafastresponseporouspoly(N-isopropylacrylamide)(PNIPAAm)gelbyusingthephaseseparationtechnique.Gotoheta1.【synthesizedthermosensitiveporousPNIPAAmandpoly(.N-diethylacryl7amide)hydrogelsbyconductingpolymerizationabovetheirLCST.Zhangeta1.【synthesizedaporoushydrog
10、elbycrosslinkingthroughthesiloxanetheswellinganddeswellingratesofhydrogelshavestructure,buttheyareonlythermosensitive.1inkageatdiscontinuoustemperature.Inallabovecases,beensignificantlyenhancedbytheformationofporousThetemperatureandpHdualsensitivehydrogelsexhibitavolumephasetransitioninresponsetopHa
11、swellastemperatureandallowthedrugtobereleasedinresponsetothechangeofpHandtemperature,therefore,theyattractgreaterinterestthanthermosensitiveoneforthedrugdeliverysystem【们.Yooeta1.【】haveCorrespondingauthor:YongzhongBao(包永忠),Email:yongzhongbaou.edu.caReceivedApril26,2005;RevisedJune22,2005;AcceptedSept
12、ember14,2005l96j.HuangelalsynthesizedaDHandtemperaturesensitivepoly(NIPAAm-co-acrylicacid)hydrogels.Otherhydrogels,whichcanberesponsetopHandtemperature.havebeenalsoprepared,suchasdextran-maleicanhydride/PNIPAAmhydridhydrogels【,poly(NIPAAm-co-MAH-,8-CD)hydrogelsandsoon.Itisknownthatthehydrogelsbearin
13、gcyanogroupsareveryusefu1fortheimmobilizationprocessviatheregio-selectiveinteractions,whichcantakeplaceatawel1.definedsiteofbiomolecules【.Unfortunately.theporoushydrogelswhichcanrespondtomultiplestimuli(temperatureandpH)areseldomreported.Acrylonitrile.acrylicacid(AN.AA)copolymerhydrogelsaresensitive
14、totemperatureandpHsimultaneouslyt15J.TheformationofporesinAN.AAcopolymerhydrogelswil1furtherincreasetheirresponserate.Inthispaper,theporousAN-AAcopolymerhydrogelwithcontrolledporousstructureswillbepreparedbythefree-radicalpolymerizationusingaliphaticalcoholsasporogens.Theporousstructure,swellingprop
15、ertiesandresponsekineticsoftheresultinghydrogelswil1beinvestigated.EXPERIMENTALMaterialsAcrylonitrile(AN)andacrylicacid(AA)usedastheprimarymonomerswerecommerciallyavailablefromWulianChemicalReagentFactory(Shanghai,China),andwerevacuumdistilledbeforeuse.N,N-methylenebisacrylamide(MBA)waspurchasedfrom
16、Fluka(Switzerland).Ammoniumpersulfate(APS),tetramethylethylenediamine(TEMED)wereusedasthepolymerizationinitiatorandaccelerator,respectively.Methanol,ethanol,butanolandoctanolwereanalyticalreagentgradeandusedasreceived.WaterusedinallthestudieswasdistilledanddeionizedtopH7.0.SrnthesisofHydrogelsAN-AAcopolymerhydrogelswereprepare
