活性自由基英文文献总结_精品文档PPT课件下载推荐.pptx
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活性自由基英文文献总结_精品文档PPT课件下载推荐.pptx
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FreeRadicalPolymerizationRadicalPolymerizationHightoleranceofgrowingradicalspeciestowardmanyfunctionalgroupsCopolymerizationsbetweenvariousmonomersarequitestraightforwardandhighmolecularweightpolymersareformedearlyRadicalpolymerizationcanbecarriedoutinawiderangeoftemperaturesandconditionsArchitecturalcontrolIonicPolymerizationcombinetheadvantagesControlledRadicalPolymerizationF.diLena,K.Matyjaszewski/ProgressinPolymerScience35(2010)9591021FreeRadicalPolymerizationControlledRadicalPolymerization(i)Therateofinitiationisfasterthanthatofpropagation,sothatallchainsformandgrowsimultaneously.(ii)Theconcentrationofactiveradicalsislowinordertoslowdownterminationreactions.(iii)Theconcentrationofpropagatingchainsishighsoonlyasmallfractionofthemareterminated.(iv)Thepolymerizationsystemremainssufficientlyhomogeneous,sothattheactivecentersarereadilyavailable.requirementsF.diLena,K.Matyjaszewski/ProgressinPolymerScience35(2010)9591021Organometallicmediatedradicalpolymerization,isbasedonthefastandreversiblehomolyticcleavageofametal-carbonbondinthemetalcomplex.Dependingonthetypeofmonomerused,thespecificmetal/ligandcombinationandtheinitiationstrategy,OMRPcanoccurthrougheitherRDCorDTorbothmechanisms.Chain-breakingreactionssuchasCCTmayalsocompetitivelytakeplace.F.diLena,K.Matyjaszewski/ProgressinPolymerScience35(2010)9591021TransitionmetalcomplexesthathavebeenreportedtopolymerizeolefinsviaaRDCmechanismincludeTi,Mo,Os,Co,andRhcompounds.reversibledeactivationbycoupling(RDC)mechanismF.diLena,K.Matyjaszewski/ProgressinPolymerScience35(2010)9591021Catalyticchaintransfer(CCT),whenitsrateissufficientlyhigh,themolecularweightdistributionoftheresultingoligomerscanbedescribedbyaShultzFlorystatistics(Mw/Mn2).EfficientCCThasbeenreportedwithcertainMo,Fe,andespeciallyCocomplexes.F.diLena,K.Matyjaszewski/ProgressinPolymerScience35(2010)9591021Catalyticchaintransfer(CCT)processDegenerativetransfer(DT)processF.diLena,K.Matyjaszewski/ProgressinPolymerScience35(2010)9591021Themethodisknownasdegenerativetransfer(DT)radicalpolymerization.Theexchangeprocessusuallytakesplacethroughashort-livedintermediatethatinsomecasescanbeconsideredatransitionstate.SincetheCoCbondcleavageofOrgano-cobalt(III)complexescanbeachievedundermildconditions,organocobaltcomplexeshavebeenusedassourcesofcarbon-centeredradicalsfororganicsynthesisandinpolymerchemistry.A.Debuigneetal./ProgressinPolymerScience34(2009)211239Additionof(TMP)CoIIreducestherateofpolymerization,andthepoly-merizationprocesscanbeeffectivelystoppedandrestartedrepetitivelybycyclingthereactiontemperaturebetween5and60.AlinearincreaseinMnwithMAconversionalongwithrelativelysmallPMApolydispersities(Mw/Mn=1.1-1.2)indicatesthatapreponderanceofthepolymerchainsaregrowinginamannercharacteristicofalivingpolymerizationprocess.(TMP)Co-CH2C-(CH3)31(TMP)Co-MA2Reactionof2withMAat60inbenzeneresultsinformationofPMAwithrelativelysmallpolydispersity(1.1-1.3)andlinearincreaseinMn(1X104to1.7X105)withMAconversion(5-80%,DP=125-2000).Inspiteoftheprocessesthatcanlimitpolymergrowth,observationoflinearincreasesinMnwithconversion,formationofblockcopolymers,andrelativelysmallpolydisper-sitiesclearlydemonstratethat1and2initiateaneffectivelivingradicalpolymerizationofacrylates.BradfordB.Wayland/J.Am.Chem.SOC.1994,116,7943-7944In2004,theWaylandresearchgroupshowedthat,inthepresenceofaradicalsourcesuchasAIBNorV-70,thepolymerizationofMAcouldbemediatedbycatalyticamountsof(TMP)Co.At60Candinbenzene,afterashortinductionperiod,PMAofmolecularweightupto120,000andpolydispersityaslowas1.06wereproduced.Lowpolydispersitypoly(MA-b-BA)copolymerswerealsoefficientlysynthesized.Mechanism(i)theinductioncorrespondstothetimerequiredtoproducesufficientradicalstoconvertalloftheCo(II)speciesintoCo(III)R,whichcontrolsthepolymerizationviaaslowRDCmechanism.(ii)ThecontinuedinfluxofradicalsfromV-70changestheprocesstoafasterDT-basedpolymerizationinwhichbothln(M0/M)vs.timeandMnvs.conversionincreaselinearly.(iii)AftertheinfluxofnewradicalsfromV-70hasended,thepolymer-izationreactionrevertstotheslowerRDCpathway.F.diLena,K.Matyjaszewski/ProgressinPolymerScience35(2010)9591021Theaccuracyoftheoreticalcalculationsintermsofmolecularstructure,energeticsandphysicalpropertieshasmadeenormousprogressinthelastcoupleofdecades.Theapplicationofcomputationaltools,especiallyDensityFunctionalTheory(DFT)methods,inviewoftheirrelativelygoodperformanceatcomparativelylowcomputationalcost,isbecomingroutineinava
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