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1、1Chapter2Radical/ChainPolymerization21ReactionsofRadicalPolymerization3ElementaryReactionsofRadicals1）Addition(加成)2)Transfer(转移)3）Coupling(偶合）4）Disproportionation（歧化）5）Fragmentation（分解）..4ReactionsofPolymerizationwhereRi*isaactivespeciesofchainlengthi,I2isth
2、einitiator(引发剂),Misthemonomer,Sisatransferagent(链转移剂),andPispolymerfast/slowfastfastslowEssenceofChainPolymerizationEachadditionreproducesthereactivegroup.(Trueforeverykindofchainpolymerization,notjustfreeradical.)R*=R•radicalpolymerizationR*=R-anionpolymeri
3、zationR*=R+cationpolymerizatione.g.coordinationpolym.ionicpolymerization62MonomersforChainPolymerization7GeneralforAllChainPolymerizationsVinylpolymerizationsworkingeneralbecauseconvertingadoublebondintotwosinglebondsisexothermic(放热).ThermodynamicsKinetics8H
4、owever,inmorehighlysubstitutedsystems,thereisstericcrowdinginthepolymerchains,andthisdecreasesthedrivingforce.-2.1MonomervsMechanismHeterolysis(异裂)Homolysis(均裂)ringopeningRadicalPolym.IonicPolym.ElectronEffect（1）X=Y=Hradicalpolymerization（2）X=H,Y=OR(electron
5、donating)（3）X=H,Y=CN,COOH,COOR(electronwithdrawing)*CH2=CHNO2canbeonlypolymerizedbyanioncation(阳离子)anion(阴离子)/radicalVinylmonomers(CH2=CHXY)11ProblemwithAlkylGroupsTheallylradical(lowerstructure)isverystable,andformspreferentially.Attemptedfreeradicalpolymer
6、izationofpropylenefails！(4)X=H,Y=Cl,Finductiveandconjunctiveeffect,radicalpolymerizationonly(5)X=H,Y=aromaticorconjunctivegroupradical/anion/cation,castyrene,butadiene(6)X=R,Y=R’,1,1-disubstitutedifbothXandYareelectrondonor/acceptor,CH2=CH(CN)2(anion),CH2=CH
7、(CH3)2(cation)ifXandYaredifferent,determinedbystrongergroupCOOCH3>CH3,radicalandanionMonomerforcoordinationpolymerizationStericeffectofsubstituteA.1,1-disubstitutedvinylmonomerRistoolargetobepolymerizedB.1,2-disubstituteddisfavorforpolymerization(electronica
8、ndsteric)C.tri-andtetra-substitutedvinylmonomersnormallyimpossible,exceptfluoroalkenePolymerizationabilityismainlydeterminedbytheelectroneffect,stericeffectshouldbealsoconsideredwhenthesubstitut
