Chapter3

FreeRadicalCopolymerization21IntroductionHomopolymerization——polymerizationofonekindofmonomer;

Copolymerization(additionpolymerization)——polymerizationofmorethanonekindofmonomer;1.1ConceptNewkindsofcopolymercanbesynthesizedbycopolymerizationofdifferentcombinationofvariousmonomers.Copolymergeneratedfromsamemonomerscanhavedifferentcompositionsandtopologies.1.2TypeofcopolymeralsoobtainedbyothermethodsNormallypreparedbyothermethodspoly(ethylene-co-propylene) 乙烯-丙烯共聚物poly(ethylene-r-propylene) 乙烯-丙烯無規(guī)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;AAorAB9EssentialPointThecompositionofacopolymerdoesnotnecessarilymatchthecompositionofthecomonomersusedinthereaction(feedratio投料比).Ethylene-vinylacetatecopolymervinylacetate% property10~20 plastic30~40 adhesive50 rubber10Possiblepropagationsequences

infree-radicalcopolymerization11assumptionsincopolymerizationtherateofthepropagationbechain-length-independent.onlytheterminalunitofthepolymerradicalcanaffectitsreactivitynosidereactions,suchasdepropagation,monomerpartitioning,andvariousformsofcomplexformation13Theoverallratesofconsumptionofmonomers[M1],[M2]thenfollowtheseexpressions:ignoretheinitiationTheexpressionforinstantaneouscopolymercomposition(F1/F2)molarfractionofM1molarfractionofM22.1CopolymercompositionequationSteady-stateassumptionMayo-LewisEquation17ExamplesNeithermonomerhomopolymerizesverywell.FormsalmostperfectlyalternatingcopolymerofhighMW.Alternatingcopolymerizationiscommoninfreeradicalreactionswhenonemonomerhaselectronwithdrawinggroupsandtheotherhaselectrondonatinggroups.18InfluneceofPolymerizationmechanismonrSt(M1)-MMA(M2)

Radical： r1=0.52, r2=0.46;Cationic： r1=10, r2=0.1;Ionic: r1=0.1, r2=6;19CopolymerequationintermsofmolefractionCopolymercompositiondependsonnotonlythemonomerfeed,butthereactivityratioaswell.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<1azeotropiccopolymerization恒比共聚copolymercompositionequalstomonomerfeedVDC(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=13.OthersTypicalcompositioncurvesr1<1andr2

<1r1>1andr2

<1r1>1andr2>1blockr1

r2=1randomr1

=r2=0alternativer1

<1,r2<1randomr1

>1,r2>1blockormixtureofhomopolymer

r1

>1,r2<1closetorandomSummery292.3Copolymercompositionwithconversionr1<1，r2>

1f1orF1conversionr1<1，r2>

1f1orF1conversion30r1<1，r2<

1f1orF1conversionf1orF1conversionr1>1，r2>131CopolymercompositionwithconversionPolymerizedmonomerMonomerbeforepolym.Monomerafterpolym.Sincefvarieswithconversion,F1alsovarieswithconversion.Therefore,theaveragecopolymercompositionshouldbeobtainedbyintegration32AveragecopolymercompositionM0=1MSt-MMAf10=0.8,f20=0.2,r1=0.53,r2=0.56F1=f1=0.48433Controllingcopolymercomposition苯乙烯-反丁烯二酸二乙酯共聚物瞬時組成與轉化率的關系(r1=0.30,r2=0.07)Whenthef10isclosetoazeotropicpoint,thecopolymercompositionslightlyvarieswithconversion(<90%).Whenthef10isfarfromazeotropicpoint,thecopolymercompositiongreatlyvarieswithconversion.Byadjusti