高分子化学（浙江大学） polymer2-2 Polymerization Rate

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1、15.PolymerizationRate25.1Macrokinetics(宏观动力学)1.MonomerConversionandRpRpC%t31.Directsampling(直接取样)weightthepolymeratdifferentintervals.2.Dilatometermethod(膨胀计法)VC3.Refractionindex(折光指数法)e.g.nPVAc-nVAc=0.0714.Spectroscopy(光谱法)MMAat1630cm-1。5.Calorimetry(量热法)HCMeasurementofRp4T

2、ypicalPolymerizationRateCurvesRpC%t①④③②Induction：decompositionofinitiatorInitial：C%=05-10，alowsteadyrateMiddle：auto-accelerationC%=5-1070-90）End：dropofrate(C%=70-90100)55.2MicroKinetics(微观动力学)Riintherangeof10-810-10mol/L.s,wherefisinitiationefficiencyKineticequation:Rpvsconc

3、entrationofreactantsInitiation6PropagationRp=10-4-10-6M·s;kp=102-104M-1·s;[M•]=10-7-10-8M;[M]=1-10mol/L[R•]=∑[Ri•]Assumingidenticalactivityofradicalswithvariouslength,sokp=kp,i.7Terminationkt=kt,c+kt,d2representstworadicalswereconsumedbyonereaction(US)disproportionationcombinati

4、on8TotalpolymerizationRateThepolymerizationdegreeissolarge,thatthemonomerconsumedintheinitiationreactioncanbeneglected,orRi<

5、ateTheconcentrationofradicalsisconstantorinitiationrateisequaltoterminationspeed.[R•]determinedbyinitiationmode10PolymerizationratewithdifferentinitiationsInitiatorSelf-initiationofStyreneln([M]0/[M])t:lowconversion;[I]andfareconstant11ActualPolymerizationratedifferentinitiatio

6、nandterminationreactionsThespecificmechanismcanbededucedbytheparametersmandn125.3InfluenceofTemperatureArrheniusEquationFornormalpolymerizationinitiatedbyinitiator:Ed125KJ/mol,Ep29KJ/mol,Et17KJ/mol,soE=83KJ/molThiscorrespondstoatwoorthreefoldrateincreasefora10oCtemperatureinc

7、rease.135.4Autoacceleration(自动加速效应)PMMApolymerizationinbenzenesolutionatvariousconcentrations.atlowconcentrations(<40%),thepolymerizationproceedssmoothlywithnounusualeffects.athigherconcentrations,apronouncedrateaccelerationafterpartialconversionofmonomertopolymer.Themoreconcent

8、ratedthesolution,theearliertheaccelerationoccur