活性自由基英文文献总结_精品文档.pptx

活性自由基英文文献总结_精品文档.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