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ID:62084146
大小:1.47 MB
页数:86页
时间:2021-04-14
《最新《聚合反应原理专论》 chapter 2(中科大研究生教学课件课件ppt.ppt》由会员上传分享,免费在线阅读,更多相关内容在教育资源-天天文库。
1、《聚合反应原理专论》chapter2(中科大研究生教学课件)§2-1Thesignificancesoflivingfreeradicalpolymerization1.ImportanceinpolymerindustryMostofpolymermaterialsareproducedbythemethodoffreeradicalpolymerizationProcessconditions:bulk,solution,suspension,emulsionpolymerizations.Medium:waterandcommo
2、norganiccompounds(2)TheneedsofcontrollingmolecularweightBigeffectsofMWandMWDonthepropertiesofpolymermaterials.Forexample,theMWofpoly(acrylonitrile)usedinmakingfiberisaround5x104,alsonarrowermolecularweightdistributionisnecessary.§2-2Differencebetweenanionicandfreeradica
3、lpolymerizationTable2-1.ComparisonoffreeradicalwithlivinganionicpolymerizationActiveSpeciesInitiationrate(mole/sec)Concofactivespecies(mol.L-1)kapp(L/mol-sec)kt(L/mol-s)τs(Sec)AnionicVeryfast10-4~10-22~3800smallLongFreeradical10-10~10-810-9~10-7102~104106~1080.1~10§2-3P
4、rogressoflivingfreeradicalpolymerization1.LivingpolymerizationsystemcontainingCr++andperoxides(1)Ageing(2)InitiationandpropagationreactionsPropagationreactionFreeradicalhasfasterinitiationandpolymerizationratescomparisonwithfreeradicalpair.(3)InitiationefficiencyRgrouph
5、asbigeffectontheactivityofradicalpair,sterichindranceofthegroupisakeyfactor.Initiationefficiency(f)=numberofradicalresiduesinthepolymer/numberofradicalsproducedKetopinylperoxide(过氧化茨烷酮酰)TheeffectofpolymerizationtemperatureTheinfluenceoftemperatureonthefvalueBPOKPO2.Init
6、iationsystembythermaldecomposition(1)ThecompoundswithtriphenylmethylgroupTheoreticalconsideration•HomolyticalsplitofC-Cbondinpolymerizationcondition•Triphenylmethylradicalsareverystableandcanexistinhighconcentration•Fastequilibrium,reducetheconcentrationofchainradicalsT
7、hereactionoffreeradicalsTheexperimentevidenceStructuralanalysisThepolymerizationinitiatedbyhexaphenylethaneWheninitiationofMA,nogoodresultwasobtainedwithtriphenylethane,probablyduetoslowinitiation.InitiationreactionThusazocompoundsweresynthesizedInitiationandpolymerizat
8、ionmechanismSomesidereactionsAnothercompoundsasinitiatorRadicalpolymerizationofMMA,St,andMALivingNormalOligome
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