Fundamental studies of grafting reactions.pdf

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1、FundamentalStudiesofGraftingReactionsinFreeRadicalCopolymerization.II.GraftingofStyrene,Acrylate,andMethacrylateMonomersontocis-PolybutadieneUsingAIBNInitiatorinSolutionPolymerizationNAI-JENHUANCandDONALDC.SUNDBERC*PolymerResearchGroup,DepartmentofChemicalEngineering,UniversityofNewH

2、ampshire,Durham,NewHampshire03824SYNOPSISGraftingcanbeinitiatedbyprimaryand/orpolymerradicalattackonthebackbonepolymeranditiswellknownthatAIBNdoesnotreadilypromotegrafting,evenwhenusingpoly-butadiene.Wehavestudiedthegraftingofseveraldifferentmonomersontocis-polybuta-dieneusingAIBNini

3、tiatorandfinddramaticallydifferentresultsamongthemonomers.Asexpected,styrenegraftsatverylowlevelsduetotheinactivityoftheinitiatorradicalsandthepolystyrylradicals.Methacrylatemonomergraftsataslightlyhigherlevelduetoitsmorereactivepolymerradical,whileacrylatemonomerreadilygraftsontothe

4、poly-butadienebecausepolyacrylateradicalsarequitereactive.Theuseofakineticmodelallowedtheevaluationofratecoefficientsforgraftsiteinitiationtobeintherelativeorderof0.1:1.0:10.0(L/mol/s)forstyrene:methacrylate:acrylatemonomers.Themodelalsopro-videdsuccessfulinterpretationsofthegrafting

5、dataanditsdependenceupontheconcen-trationsofmonomer,initiator,andbackbonepolymer.Duetotherelativelyhigherreactivityofthepolyacrylateradicals,thebenzenesolventactedasachaintransferagentinthissystem.Thisaffectedthemolecularweightofbothfreeandgraftedacrylatepolymerandalsosurpressedthegr

6、aftlevel.Polyacrylateradicalsattackthecis-polybutadienebackbonebyabstractinganallylichydrogenandalsoaddingacrosstheresidualdoublebond.Thelattermechanismisresponsibleforthemajorityofthegrafting;thehydrogenabstractionleadstorelativelyinactiveradicalswhichcausearetardationintheoverallre

7、actionrate.01995JohnWiley&Sons,Inc.Keywords:graftingcis-polybutadienestyreneacrylatemethacrylateAIBNINTRODUCTIONSincethen,thesocalledhigh-impactpolystyrene(HIPS)andtherubber-toughenedSAN(acryloni-Polymermaterialswithnewpropertiescanbeob-trile-butadiene-styrene,ABS)havegainedbroadtain

8、edeitherbyth