高分子化学课件polymer3 1new

Chapter3

FreeRadicalCopolymerization21IntroductionHomopolymerization——polymerizationofonekindofmonomer;

Copolymerization(additionpolymerization)——polymerizationofmorethanonekindofmonomer;1.1ConceptNewkindsofcopolymercanbesynthesizedbycopolymerizationofdifferentcombinationofvariousmonomers.Copolymergeneratedfromsamecomonomerscanhavedifferentcompositionsandtopologies.4ExamplesStyreneStyrene+AcrylonitrileStyrene+ButadieneStyrene+Acrylonitrile+ButadienePSSANSBRABSBrittle,transparent,poorsolventtolerationHighimpact,goodsolventtolerationHighelasticityEngineeringplasticsMaleicanhydrideStyrene+maleicanhydrideNopolymerSMA1.2TypeofcopolymeralsoobtainedbyothermethodsNormallypreparedbyothermethodspoly(ethylene-co-propylene), 乙烯-丙烯共聚物poly(ethylene-r-propylene), 乙烯-丙烯无规共聚物poly(ethylene-b-propylene), 乙烯-丙烯嵌段共聚物poly(ethylene-g-propylene), 乙烯-丙烯接枝共聚物poly(ethylene-a-styrene), 乙烯-苯乙烯交替共聚物1.2NomenclatureofcopolymerKeytopicsincopolymerization-ABABBAABABBAAABABA-Composition

distributiontherelativeamountsofeachmonomerunitincorporatedintothecopolymer,A%orB%Sequencedistributionthewayinwhichthesemonomerunitsarearrangedwithinapolymerchain;-AAor-AB82.Copolymercomposition9EssentialPointThecompositionofacopolymerdoesnotnecessarilymatchthecompositionofthecomonomersusedinthereaction(feedratio).ethylene-vinylacetatecopolymervinylacetate% property10~20 plastic30~40 adhesive50 rubber10Possiblepropagationsequences

infree-radicalcopolymerization11assumptionsincopolymerizationtherateofthepropagationbechain-length-independent.onlytheterminalunitofthepolymerradicalcanaffectitsreactivitynosidereactions,suchasdepropagation,monomerpartitioning,andvariousformsofcomplexformation12Reactionsincopolymerization13TheoverallratesofconsumptionofmonomersM1/M2thenfollowtheseexpressions:ignoretheinitiationTheexpressionforinstantaneouscopolymercomposition(F1/F2)molarfractionofM1molarfractionofM22.1CopolymercompositionequationSteady-stateassumptionMayo-LewisEquation16ReactivityratioSpecialcases:r1=0andr2=0Eachcomonomerpreferstoreactwiththeother.Perfectlyalternatingcopolymer.r1>1andr2>1Eachcomonomerpreferstoreactwithothersofitsownkind.Tendencytoformblockcopolymers.r1*r2=1Thereisnopreferenceduetothechainends.Randomincorporationofcomonomers;"Ideal"copolymerization.Theratioofratecoefficientofhomopolymerizationtocopolymerization1homopolymerizaitoncopolymerizaitonr17ExamplesNeithermonomerhomopolymerizesverywell.FormsalmostperfectlyalternatingcopolymerofhighMW.Alternatingcopolymerizationiscommoninfreeradicalreactionswhenonemonomerhaselectronwithdrawinggroupsandtheotherhaselectrondonatinggroups.

18EffectofPolymerizationmechanismonrSt(M1)-MMA(M2)

Radical： r1=0.52, r2=0.46;Cationic： r1=10, r2=0.1;Ionic: r1=0.1, r2=6;19CopolymerequationintermsofmolefractionCopolymercompositiondependsonnotonlythemonomerfeed,butthereactivityratioaswell.2001r1r1>1ork11>k12tendtohomo-thancopolymn.r1<1ork11<k12tendtoco-thanhomopolymn.r1=0ork11=0onlycopolymn.VariationofreactivityratioFisthefunctionofbothrandf2.2

Copolymercompositioncurver1=

ork11>>k12onlyhomopolymn.butadiener1=1.39,styrener2=0.781.Idealcopolymerization(r1*r2=1)Typicalcopolymercompositioncurves0.10.20.512510r1<1r1>122A.r1=r2=1B.r1<1,r2>1C.r1>1,r2<1azeotropiccopolymerizationcopolymercompositionequalstomonomerfeedVDC(偏氯乙烯)-MMA, r1=1.0,r2=1.0Acrylamide(丙烯酰胺)-丙烯酸甘油酯, r1=1.0,r2=1.0Ethylene-VAc r1=1.07,r2=1.0823CharacteristicsofidealcopolymerizationThereisnopreferenceduetothechainends.Randomincorporationofcomonomers."Ideal"copolymerizationr1*r2=12.Alternativecopolymerization(r1=r2=0)TypicalcompositioncurvesEachcomonomerpreferstoreactwiththeother.Perfectlyalternatingcopolymer.

copolymercompositionindependentonmonomerfeedIfr2=0andr1

0[M2]>>[M1][M2]~[M1]St/MMAinitiatedbyBPO/AlR33.OthersTypicalcompositioncurvesr1<1andr2

<1r1>1andr2

<1r1>1andr2>1blockr1

r2=1randomr1

=r2=0alternativer1

<1,r2<1randomr1

>1,r2>1blockormixtureofhomopolymer

r1

>1,r2<1closetorandomSummeryAzeotropiccompositionDefinition:Togetsolution,itshouldbethatr1andr2>1orr1andr2<1Independentonmonomerconversion292.3CopolymercompositionunderconversioninstantaneouscopolymercompositionSincefvarieswithconversion,F1alsovarieswithconversion.Therefore,theaveragecopolymer