1、RAFT-based living radical polymerizationRAFT: reversible addition-fragmentation chain transfer process.1998: patent1998: first paperIntroductionIntroductionThe first paper:RAFT process:t1t2t3MechanismCSZSRInitiation: traditionalIkd2 RRAFT processPropagationTerminationR + MkiP1R1+ MkiP1SSPmPn+SSPmPnS
2、SPn+PmkaddkfrgkaddkfrgPi+ MkpPi+1Pi + CZSSPnPmktCZSSPnPmPiR1: fragment of dithioestersn=m; nm; m=0Pn+ PmktPn+m / Pn + PmElementary ReactionsMore complex mechanismMore complex mechanismCoote summarizeda model composedof 49 elementaryreactions.Kinetic study veryDifficult !Evidence supporting the RAFT
3、mechansimEnd-group analysis by NMR: retaining of thiocarbonylthio moietyCSIRO, Aus. J. Chem. 2005, 58, 379-410.Evidence supporting the RAFT mechansimCSIRO, Aus. J. Chem. 2005, 58, 379-410.End-group analysis by MALDI-TOF MS:Evidence supporting the RAFT mechansimCSIRO, Aus. J. Chem. 2005, 58, 379-410.
4、Observation of the intermediate by EPR:Structure-activity:C SSCCH3CH3DithiocarbamatesC S CHCH3SC SSC CH3CH3CNC S CHCH3SCH2CSZSRN CSS RSSCOOHCNCH2S C NSC2H5C2H5S C SSCH2PhPhCH2C SSCH2Thiocarbonylthio compoundstrithiocarbonatesDithioestersxanthatesStructure-propertyThe overall reaction of the RAFT pol
5、ymerization:CSZSRR-effect:Z-effect:Steric R- tends to activate, electron-donating Z- tends todeactivate, whyStructure-propertyab initio quantum calculation: a direct method Summary and outlookSynthesis of thiocarbonylthio compounds2. From thiols1. By Grignard reagent: Synthesis of thiocarbonylthio c
6、ompounds3. From alkylhalides4. Via esterificationSynthesis of thiocarbonylthio compounds5. Via radical reaction of bis(thiocarbonyl) disulfidesSummary and outlookSynthesis of thiocarbonylthio compoundsFrom bis(thiocarbonyl) disulfide:Summary and outlookSimilar methodsFor xanthates:Zard, S. Z.; et al
7、Summary and outlookSynthesis of thiocarbonylthio compoundsLai:Commercialization: PTC: phase transition catalystPolymerization rate:depends on initiator concentration010203040500.00.51.01.52.0 lnM0/MtTime (hours) CDB 10mM AIBN 3mM CDB 10mM AIBN 6mM CDB 10mM AIBN 9mMSummary and outlookKinetic featureM
8、olecular weight: linear increase with conversion inverse proportional to ZSSR001020304050600100002000030000400005000060000 MnConversion (%) CDB 5mM AIBN 3mM CDB 10mM AIBN 3mM CDB 15mM AIBN 3mM TheoreticSummary and outlookKinetic featureSummary and outlookMWDsSummary and outlookMn and PDI evolution w
9、ith conversionProduct structure15161718192021222324250100200300400500 18 hours 7 hours 3 hours PMMA-DIR Detector ResponceRetention time (min)PMMA-b-PS:Summary and outlookBlock copolymerizationPhenomenon:Perrier, S.; Davis, T. P. et al Macromolecules 2002, 35, 8300Retardation and incubationTwo mechan
10、isms: slow fragmentation and cross terminationSlow fragmentation: Davis and Barner-kowollikSSPmPn+SSPmPnSSPn+Pmkaddkfrgkaddkfrg1. -radiation2. Computer simulation3. ab initio calculation of molecular obitalKfrg=10-2 s-1Retardation and incubationCross termination: Monteiro and FukudaPi + CZSSPnPmktCZ
11、SSPnPmPiKfrg=104 s-1Kwak, Y.; Fukuda, T. et al Macromolecules 2004, 37, 4434. de Brouwer, H.;Monteiro, M. J.;German, A. L. J. Polym. Sci., Part A: Polym. Chem. 2000, 19, 3596. Origin of the retardationPeople are concerning Broad range: styrene and its derivatives, MA, MMA, BA, etc.But vinyl acetate,
12、 acrylamide do not give good resultsMonomer applicableThe selectivity between RAFT agentsand monomersDithioesterstrithiocarbonatesXanthates (dithiocarbonates)dithiocarbarmatesMore activated monomers (MAM)Less activated monomers (LAM)Styrene, MMA, MAVAc, NVP, NVCTo synthesize block copolymers: poly(M
13、AM)-b-poly(LAM), the sequence should be MAM LAM.However, difficult to do with the same RAFT agents !Guidelines for selection of RAFT agentsDashed lines indicate partial control.Universal (switchable) RAFT agentPolymerization resultsBlock copolymersABA TriblockPS-PBA-PSRizzardo and Solomon win the pr
14、izeABA TriblockPS-PBA-PSRizzardo and Solomon win the prizeHomopolymer with functional groups: narrow disperseBlock copolymersStar-like polymersGradient copolymersEnd-group removalApplicationFunctional polymers by RAFTEnd-group removal and functionalizationHydrolysis or aminolysis.End-group removal a
15、nd functionalizationHydroxylationBy an unbelievable reaction:PPh3Pn-OHESI MS of the product with OH endBlock copolymers from hydroxy-productThiocarbonylthio moieties with electron deficient Z-groupsHeteroatom Diels-Alder reactionDirect bonding to metal surfaceTo gold surfaceThiocarbonylthio or thiol
16、 ?Synthesis of block copolymersAB diblock:Important: order selection (e.g., PMMA-b-PS) the first block be good leaving groupotherwise, feed addition protocol to keep low concentration of monomer, then PS-b-PMMA is possible.Synthesis of ABA triblock copolymersABA TriblockPS-PBA-PSABA triblock copolym
17、ersDiscussThe synthetic route; Mixture of star and linearStenzel-Rosenbaum, et al, J. Polym. Sci. Part A: Polym. Chem. 2001,39, 2777Star-like polymersMulti-modal distributionSynthesis of star-like polymerONH2PolymerizationConditions:Buffered mediumCH3COOH /CH3COONaat pH = 5.0Initiator:VA-086McCormic
18、k, C. L.; et alMacromolecules2001, 36, 1436RAFT polymerization in water phaseONH2SSNOSO3NaHC NNOOH2HMonomerCTAInitiatorconditions &controllabilityreferenceAcOH/AcONaBufferpH = 5.0d=1.03Macromolecules2003, 36, 1436CCH3CNCH2CH2COOHN2ONHNCH2NCH3H3CCH3SSCOOHCNMacromolecules2004, 37, 2728VA-086VA-501ibidibidBufferpH = 5.0d1.1ibidibidAcidic Buffer prevents the hydrolysis of dithioesterby amine group in monomerRAFT in water phaseHigh pressure RAFT
