高分子化学（浙江大学） polymer2-3 Measurement of rate coefficients

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1、18.Measurementofratecoefficients2HistoryUptothelate1980sterminationandpropagationratecoefficientswereaccessibleonlyintheircoupledform,kp/kt0.5orindividuallyviacombinationwithpseudoflickeringtechniquesliketherotatingsectororspatiallyintermittentpolymerizationmethodsincombinationwithstationarypo

2、lymerizationmeasurements.Thesituationhasdramaticallyimprovedwiththeinventionofthepulsedlaserpolymerization(PLP)techniqueinthelate1980s.Sincethen,thistechniquehasbeenextensivelyusedtocollatepropagationandterminationratecoefficientsforvarioushomo-andcopolymerizations.38.1MethodsfortheMeasurement

3、ofkdRd=fkd[I]Theconcentrationcanbemeasuredviaanyquantitytowhichitisdirectlyproportional,suchasaspectroscopicinfrared(红外光谱)absorptionthatcanbeeasilyfollowedwithreactiontime.Infraredspectroscopyhasbeenusedextensivelyinthepasttostudythedecayoforganicperoxidesinvariousreactionmedia.48.2Methodsfort

4、heMeasurementofkpPulsedLaserPolymerization–Size-ExclusionChromatography(PLP-SEC)L0L0+2L0L0+2L0+3L0irradiatedbyapulsedlaserbeam(5-20ns)Monomerphotoinitiator,(solvent&transferagents)MWofpolymerproducedbyPLP:L0,n=nkp[M]t0568.2MethodsfortheMeasurementofkpElectronSpinResonanceSpectroscopy-Stationar

5、yPolymerization(ESR)(电子自旋共振)78.2MethodsfortheMeasurementofkpQuenchedInstationaryPolymerizationSystems(QUIPS)Aphotopolymerizablemixturepassesthroughacapillarysystem,isirradiatedataspecificlocation,andpolymerizesinthecapillaryduringawell-defineddarkperioduntilitdropsintoaquenchingbathwithaninhib

6、itor(nitroxylradicals).Measuringthechainlengthdistributionbysize-exclusionchromatographythatallowsdeterminationofkpinaccordancewiththeequation.L=kp[M]t088.3MethodsfortheMeasurementofktrMayomethodTheusualprocedureformeasuringthechaintransferconstantCTinvolvesdeterminationofXnforarangeof[T]/[M]v

7、aluesandplottingthedataas1/Xnversus[T]/[M],thatis,aMayoplot.ThevalueofCTisthendeterminedasthestraight-lineslopeofthisplot.98.4MethodsfortheMeasurementofktSinglePulse–PulsedLaserPolymerization(SP-PLP)10Applyingpulsedlaser-polymerization(