第三章自由基共聚合ppt课件.ppt

1 Chapter3FreeRadicalCopolymerization 2 1Introduction Homopolymerization polymerizationofonekindofmonomer Copolymerization additionpolymerization polymerizationofmorethanonekindofmonomer 1 1Concept Newkindsofcopolymercanbesynthesizedbycopolymerizationofdifferentcombinationofvariousmonomers Copolymergeneratedfromsamemonomerscanhavedifferentcompositionsandtopologies 4 Examples StyreneStyrene AcrylonitrileStyrene ButadieneStyrene Acrylonitrile Butadiene PSSANSBRABS Brittle transparent poorsolventtolerationHighimpact goodsolventtolerationHighelasticityEngineeringplastics MaleicanhydrideStyrene maleicanhydride NopolymerSMA 1 2Typeofcopolymer alsoobtainedbyothermethods Normallypreparedbyothermethods poly 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 3Nomenclatureofcopolymer Keytopicsincopolymerization ABABBAABABBAAABABA Compositiondistributiontherelativeamountsofeachmonomerunitincorporatedintothecopolymer A orB Sequencedistributionthewayinwhichthesemonomerunitsarearrangedwithinapolymerchain AAorAB 8 2 Copolymercomposition 9 EssentialPoint Thecompositionofacopolymerdoesnotnecessarilymatchthecompositionofthecomonomersusedinthereaction feedratio投料比 Ethylene vinylacetatecopolymervinylacetate property10 20plastic30 40adhesive50rubber 10 Possiblepropagationsequencesinfree radicalcopolymerization 11 Assumptionsincopolymerization therateofthepropagationbechain length independent onlytheterminalunitofthepolymerradicalcanaffectitsreactivitynosidereactions suchasdepropagation monomerpartitioning andvariousformsofcomplexformation 12 Reactionsincopolymerization 13 Theoverallratesofconsumptionofmonomers M1 M2 thenfollowtheseexpressions ignoretheinitiation Theexpressionforinstantaneouscopolymercomposition F1 F2 molarfractionofM1 molarfractionofM2 2 1Copolymercompositionequation Steady stateassumption Mayo LewisEquation 16 Reactivityratio 竞聚率 Specialcases r1 0andr2 0Eachcomonomerpreferstoreactwiththeother Perfectlyalternatingcopolymer r1 1andr2 1Eachcomonomerpreferstoreactwithothersofitsownkind Tendencytoformblockcopolymers r1 r2 1Thereisnopreferenceduetothechainends Randomincorporationofcomonomers Ideal copolymerization Theratioofrateconstantofhomopolymerizationtocopolymerization 17 Examples Neithermonomerhomopolymerizesverywell FormsalmostperfectlyalternatingcopolymerofhighMW Alternatingcopolymerizationiscommoninfreeradicalreactionswhenonemonomerhaselectronwithdrawinggroupsandtheotherhaselectrondonatinggroups 18 Influneceofpolymerizationmechanismonr St M1 MMA M2 Radical r1 0 52 r2 0 46 Cationic r1 10 r2 0 1 Ionic r1 0 1 r2 6 19 Copolymerequationintermsofmolefraction Copolymercompositiondependsonnotonlythemonomerfeed butthereactivityratioaswell 20 0 1 r1 r1 1ork11 k12tendtohomo thancopolymn r1 1ork11 k12tendtoco thanhomopolymn r1 0ork11 0onlycopolymn Variationofreactivityratio Fisthefunctionofbothrandf 2 2Copolymercompositioncurve r1 ork11 k12onlyhomopolymn butadiener1 1 39 styrener2 0 78 1 Idealcopolymerization r1 r2 1 Typicalcopolymercompositioncurves r1 1 r1 1 22 A r1 r2 1 B r11 C r1 1 r2 1 azeotropiccopolymerization恒比共聚copolymercompositionequalstomonomerfeed VDC 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 VAcr1 1 07 r2 1 08 23 Characteristicsofidealcopolymerization Thereisnopreferenceduetothechainends Randomincorporationofcomonomers Ideal copolymerization r1 r2 1 2 Alternativecopolymerization r1 r2 0 Eachcomonomerpreferstoreactwiththeother Perfectlyalternatingcopolymer copolymercompositionindependentonmonomerfeed Ifr2 0andr1 0 St MMAinitiatedbyBPO AlR3 Typicalcopolymercompositioncurves 3 Others r1 1andr2 1 r1 1andr2 1 r1 1andr2 1 block Typicalcopolymercompositioncurves r1r2 1randomr1 r2 0alternativer11 r2 1blockormixtureofhomopolymerr1 1 r2 1closetorandom Summary 27 Azeotropiccomposition恒比组成 Definition Togetsolution itshouldbethatr1andr2 1orr1andr2 1 28 Independentonfeedratio 29 2 3Copolymercompositionwithconversion r11 r1 1 r2 1 30 r1 1 r2 1 f1orF1 conversion r1 1 r2 1 31 Copolymercompositionwithconversion Polymerizedmonomer Monomerbeforepolym Monomerafterpolym Sincefvarieswithconversion F1alsovarieswithconversion Therefore theaveragecopolymercompositionshouldbeobtainedbyintegration 32 Averagecopolymercomposition M0 1M St MMAf10 0 8 f20 0 2 r1 0 53 r2 0 56 F1 f1 0 484 33 Controllingcopolymercomposition 苯乙烯 反丁烯二酸二乙酯共聚物瞬时组成与转化率的关系 r1 0 30 r2 0 07 Whenthef10isclosetoazeotropicpoint thecopolymercompositionslightlyvarieswithconversion 90 Whenthef10isfarfromazeotropicpoint thecopolymercompositiongreatlyvarieswithconversion Byadjustingfeedratio Addingrelativelyactivecomonomerduringpolymerization 34 Controllingcopolymercomposition St Bdcopolymercompositionwithconversion Bycontrollingmonomerconversion Bd ANcopolymercompositionwithconversion 35 2 4Copolymermicrostructureandcompositiondistribution Chain lengthdistribution Monomersequencedistribution 36 Monomerdistributionandpolymerpropertiy A randomcopolymeraverageofbothpolymerAandB AAABBABBAABBBABAAB B blockcopolymermixtureofpolymerAandB AAAAAAAABBBBBBBBBBBAAAAAAAAAAA 37 Chain lengthdistributionbyProbability ForformationofM1M1fromM1 so TheprobabilitytofindblockM2 M1 xM2 TheprobabilitytofindblockM1 M2 xM1 38 Number fractiondistribution Weight fractiondistribution 39 Number averagechainlength Ontheotherhand 40 Specialexamples Whenr1 r2 0 Whenr1 r2 1 and M1 M2 41 Derivationofcopolymercompositionequation M1M1 vsM2M1 Depolymerizationeffect Forcopolymerizationinvolving methylstyrene Terminaleffectvspenultimateeffect 42 3 Multi componentcopolymerization 43 Terpolymerization ThreeinitiationreactionsNinepropagationreactionsSixterminationreactionsSixreactivityratios Ethylene propylene vinylidenenorbornene 44 4 Experimentalevaluationofreactivityratios 45 4 1Methodformeasurementofreactivityratio Byfittingcopolymercompositioncurvewithvariousr1andr2 SincetheFisnotsensitivetothevariationofr thismethodisnotsogood 46 Linecross Plotr2vsr1withdifferent M1 M2 andF1 F2 47 Fineman Rossmethod 48 4 2Variationofreactivityratio Effectoftemperature Activeenergyofhomopolymerization Activeenergyofcopolymerization SinceE11andE12arelow theirdifferenceisalsolow Sothereactivityratiovariesslightlywithtemperature Inthecaseofr1E12 astemperatureincreases k11increasemorefasterthank12 sor1increasesandapproachtounit Inthecaseofr1 1 asastemperatureincreases r1decreasesandapproachtounit 49 EffectofPressure Sameastemperature Effectofsolvent EffectofpH 50 5 Monomerstructureandthecopolymerizationreactivity 51 5 1Relativereactivityofmonomer Withrespecttosameradical themonomerreactivitycanbeevaluated TocomparethereactivityofAN M1 VAc M2 St M3 ThereactivityofVAcisonefourthofthatofAN ThereactivityofStis25timesofthatofAN ThereactivityofStis100timesofthatofVAc 52 Sothe1 r1canbeappliedtoestimatethemonomerreactivity Thelargerthereciprocalofr1 thehigherthereactivityofM1comparedtoM2 Themonomerreactivitydecreasesintheorderof St AN VAc 100 4 1 53 Withrespecttosamemonomer theradicalreactivitycanbeevaluated TocomparethereactivityofSt andVAc ThereactivityofVAc is1586timesofthatofSt k11 145L mol s k22 2300L mol s 5 2Relativereactivityofradical 54 Generalrules Monomerwithlowreactivity VAc generatescorrespondingradicalwithhighreactivity VAc Monomerwithhighreactivity St generatescorrespondingradicalwithlowreactivity St Therateofcopolymerizationismainlydeterminedbythereactivityoftheradical 55 Thesubstitutegroupaffectsreactivityofradicalstrongerthanmonomer FromTable3 8inthetextbook 5 3Influenceofsubstituteonthemonomer radicalreactivity Monomerreactivity Radicalreactivity 56 ForCH2 CHXResonanceeffect strongweakMonomerreactivity highlowRadicalreactivity lowhigh Resonanceeffect 57 Reactiontendency RS M RS MS R M R MS S Withresonanceeffect RS MS R M Homopolymerizationofmonomerwithoutresonanceeffectisfasterthanmonomerwithresonanceeffect RS M R MS CopolymerizationofM MorMs MsisbetterthanM Ms 58 CanVAcandStbewellcopolymerized Good Poor 59 Polarityeffects Monomerwithelectron withdrawingsubstitutehastendencytocopolymerizewithmonomerwithelectron donatingsubstitute infavorofformingalternativecopolymer 60 Charge transferinteractionHomopolymerizationofthecharge transfercomplexordonor acceptorcomplex 61 Stericeffect noinfluenceonmono or1 1 disubstitutedvinylmonomer1 2 disubstitutedmonomercanbecopolymerizedwithmonomerwithlessstericeffect Stericeffectplaysamoreimportantroleinhomopolymerizationthancopolymerization 62 6 Q econcept 63 Q escheme Tosimplifytheprocessofdeterminereactivityratios asemiempiricalrelationshiphasbeendevelopedthatexpressestheratiosintermsofconstantsthatarecharacteristicofeachmonomerbutindependentofcomonomer P1andQ2aremeasuresofthereactivityofradicalandmonomerrelatedtoresonancestabilization e1ande2aremeasuresofthepolarityoftheradicalandmonomer 64 StyrenewaschosenasthestandardandassignedvalueofQ 1 00ande 0 80 ValueofQincreasewithincreasingresonancestabilization whileevaluebecomelessnegati