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KineticStudyandNewApplicationsofUVRadiationCuringChristianDeckerDe´partementdePhotochimieGe´ne´rale(UMR-CNRSN87525),EcoleNationaleSupe´rieuredeChimiedeMulhouse,Universite´deHaute-Alsace,3,rueWerner,68200Mulhouse,FranceE-mail:c.decker@uha.frKeywords:crosslinking;infraredspectroscopy;interpenetratingpolymernetworks(IPN);nanocomposites;photopoly-merization1IntroductionLight-inducedpolymerizationofmultifunctionalmono-mersoroligomers,alsocalledUVradiationcuring,hasbecomeawell-acceptedtechnologywhichhasfoundalargevarietyofindustrialapplicationsbecauseofitsuniqueadvantages.[1–4]Itisconsideredtobethemosteffectivewaytorapidlytransformasolvent-freeliquidresinintoasolidpolymer,atambienttemperature.Underintenseillu-mination,thecrosslinkingpolymerizationofacrylate-basedresinsproceedsextensivelywithinafractionofasecondtogenerateadensethree-dimensionalpolymernetwork,showingexcellentresistancetowardorganicsolvents,chemicalsandheat.[5]CrosslinkingcanalsobereadilyachievedbyUVirradiationofasolidpolymerbearingpolymerizablefunctions,asshowninScheme1.Inbothcases,aphotoinitiatorisneededtogeneratetheactivespecies(freeradicalsorprotonacid),whichwillinitiatethechainreaction.ThemostimportantapplicationsofUVradiationcuringaretobefoundinthecoatingindustryforthesurfaceprotectionofvariousmaterialsbyfast-dryingvarnishes,paintsorprintinginks.UV-curablesystemsarealsoincrea-singlyutilizedasquick-settingadhesives,sealants,releasecoatings,aswellastoproducecompositematerials.InFeatureArticle:Highlycrosslinkedpolymerscanberea-dilysynthesizedbyphotoinitiatedpolymerizationofmulti-functionalmonomersorfunctionalizedpolymers.Thereactioncanbefollowedinsitubyreal-timeinfrared(RT-IR)spectroscopy,atechniquethatrecordsconversionversustimecurvesinphotosensitiveresinsundergoingultrafastpolymerizationuponUVexposure.Foracrylate-basedresins,UV-curingproceedswithlongkineticchains(7700mol/radical)inspiteofthehighinitiationrate.RT-IRspectro-scopyprovedveryvaluableinassessingtheinfluenceofvariousparameters,suchasinitiationefficiency,chemicalstructureofthetelechelicoligomer,lightintensity,inhibitoryeffectofoxygen,onpolymerizationkinetics.Interpenetrat-ingpolymernetworkscanberapidlysynthesizedbymeansofUVirradiationofamixtureofdifunctionalacrylateandepoxymonomersinthepresenceofbothradicalandcationic-typephotoinitiators.ThesameUVtechnologycanbeappliedtocrosslinksolidpolymersatambienttemperature,whichbeardifferenttypesofreactivegroups(acrylateandvinyldoublebonds,epoxyring).UVradiationcuringhasbeensuccessfullyusedtoproducewithinsecondsweatheringresistantprotectivecoatings,high-resolutionreliefimages,glasslaminatesandnanocompositesmaterials.Photoinitiatedcrosslinkingpolymerization.Macromol.RapidCommun.2002,23,1067–10931067Macromol.RapidCommun.2002,23,No.18WILEY-VCHVerlagGmbH&Co.KGaA,Weinheim,20021022-1336/2002/1812–1067$17.50þ.50/0Scheme1.Photoinitiatedcrosslinkingpolymerization.photolithography,light-inducedinsolubilizationofphoto-resistsisbeingusedtoproducehigh-definitionimagesneededforthemanufactureofprintingplates,opticaldisksandmicrocircuits.Besidesitsgreatspeedandspatialresolution,light-inducedpolymerizationpresentsanumberofotheradvantages,suchassolvent-freeformulations,lowenergyconsumption,ambienttemperatureoperations,andtailor-madepropertiesofthephotocuredpolymers.TherearetwomainclassesofUV-curableresins,depen-dingwhetherthechainreactionproceedsbyaradical-typeorcationic-typemechanism(Table1).Inthefirstcase,aromaticketonesareusedtogeneratefreeradicalsthatwillinitiatethepolymerizationofacrylatedoublebondsorcopolymerizationofstyrenewithunsaturatedpolyestersorofthethiol-polyenesystembyastep-growthadditionmechanism.[6]Inphotoinitiatedcationicpolymerization,aprotonacidisproducedbyphotolysisoftriarylsulfonium(TAS)ordiaryliodoniumsaltstoinitiatethepolymerizationofepoxidesorvinylethers.[7]Radical-typesystemsarebyfarthemostwidelyusedintoday’sUV-curingapplications,mainlybecauseoftheirhigherreactivity.ThelargechoiceofacrylatemonomersandtelechelicoligomersalsoallowstoadjustmorepreciselythefinalpropertiesoftheUV-curedpolymerfortheconsideredapplication.Duringthelastdecade,aconsiderableamountofacade-micworkhasbeendevotedtoUVradiationcuring,withmostoftheresearcheffortsbeingfocusedbothonthekineticandmechanisticaspectsofsuchcrosslinkingreac-tionsandonthedesignofnewphotoinitiators,monomersandtelechelicoligomers,bestsuitedtoproducinghigh-performancepolymernetworks.Anumberoftextbooksandreviewarticleshavereportedtheprogressmadeinthisareaoverthepastfewyears.[1–19]Inthispaper,therecentworkdoneinourlaboratory,regardingkineticsofultrafastphotoinitiatedpolymerizationofvariousmonomers,func-tionalizedoligomersorpolymersandmonomerblends,isreviewedbeforepresentingsomepromisingnovelapplica-tionsofthisenvironmentallybenigntechnology.ChristianDeckerhasbeenResearchDirectorattheCNRS(CentreNationaldelaRechercheScientifique)since1980attheEcoleNationaleSupe´rieuredeChimiedeMulhouse,andheadofthePolymerPhotochemistryLaboratoryattheDepartmentofPhotochemistry(UniversityofHauteAlsace).Hereceivedhisdoctoraldegre