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Influenceoftemperature-inducedcoalescenceeffectsonco-continuousmorphologyinPCL/PSblendsPierreSarazin,BasilD.Favis*Polymer46(2005)5966–5978Macromolecularengineering:FromrationaldesignthroughprecisemacromolecularsynthesisandprocessingtotargetedmacroscopicmaterialpropertiesKrzysztofMatyjaszewski*Prog.Polym.Sci.30(2005)858–875Questions1.Effectsonco-continuousmorphologyofimmisciblepolymerblendssuchPS/PCL,PLLA/PCL,etc.2.Relationshipsbetweenmorphologiesandwelldefined(co)polymers.Somerecentunprecedentedadvancesincontrolovervariouspolymerizationsystems,includingionic,radical,coordinationandevenpolycondensationhaveenabledsynthesisofmanynewwell-defined(co)polymersandsomeofthemarebrieflydiscussed.Precisecontrolofvariousaspectsofmacromoleculararchitecture,includingtopology,functionalityandmicrostructurehavebeenachievedbothinhomogeneousandheterogeneouspolymerizationsystemandappliedtopreparationofpolymerichybrids,conjugatesandotherfunctionalmaterials.Thewell-defined(co)polymersself-assemblyorcanbepre-assembledtomaterialswithpreciselycontrolledmorphologieswhichcanbeaffectedandfixedbyprocessing.Thefinalmacroscopicmaterialspropertiesdependonmolecularstructureof(co)polymersandcanberationallyretro-designed.1Controlled/livingpolycondensation2.Controlled/livingchaingrowth3.Controlledmicrostructures4.Complexmacromoleculararchitecture5Polymerizationinconfinedspaceandinheterogeneousmedia6.Hybridsandconjugates7.Controlledmorphologies8.Fixingmorphologies9.Pre-assembly10.Correlationbetweenmolecularstructureandmacroscopicproperties.Theconversionfromastep-growthtoachaingrowthprocesshasbeenaccomplishedbydifferentiationofthereactivityoffunctionalgroupsinthemonomerandthechainends.Ifadeactivatinggroupinthemonomer,suchasthep-phenoxygroup,isreplacedbyanethergroupatthepolymerchainend,subsequentreactionwithmonomerisfasterthanreactionbetweentwomonomerunits.Additionalcontrolisassuredbyap-ketonegroupintheinitiator,whichacceleratesthenucleophilicaromaticsubstitutionandassuresfastinitiation1Microstructure,intermsofsequencedistributionandtacticity,isbestcontrolledincoordinationpolymerizationandthereforethebestcontrolledsystemsarelimitedtothepolymerizationofolefinsandothernon-polarmonomers.Thecontrolofsequencesandtacticityinconventionalfreeradicalpolymerizationinthepresenceofvariousadditiveswerereportedrecently.Anotherpossibilityforchangingthesequencedistributionofcomonomers,beyondtheestablishedreactivityratios,isbycomplexingmonomerswithLewisacids.3Itreliesonformingequilibriabetweenactivespecies(anions,cations,radicalsandorganometallicspecies)andvarioustypesofdormantspecies.Thisapproachwasoriginallyintroduced30yearsagoforthering-openingpolymerizationoftetrahydrofuranbuthasmorerecentlybeenadoptedtocontrolcationic,anionic,coordinationandradicalpolymerization.Verysmallamountsoftheactivespecies(fromw1ppmtow1%)equilibratedynamicallywiththedormantspecies.Thisslowsdowntherateofpolymerization,requireslesscatalyst,reducingthecostoftheprocess,allowshighertolerancetoimpuritiesanddecreasescontributionsofchainbreakingreactions2Thedevelopmentofthenewcontrolled/livingpolymerizationsystemsopenedanavenuetopreciselymanipulatemanyaspectsofmacromoleculararchitectureintermsoftopology,compositionandFunctionality.Anionicpolymerizationisthemostpreciseandpowerfulinthisrespect,butrecentprogressincontrolledradicalpolymerizationadditionallyhasopenedthepossibilityofusingmanyunprotectedfunctionalmonomers,andalsofacilitatedcross-propagationtoyieldmanynewgradientcopolymers.Perhapsthemostimpressiveiscontrolofthecompositionandtopologyofmolecularbrushes.Bottle-brushcopolymerswithvariousshapes,compositionsanddensityofgraftinghavebeenprepared,andthesecanleadtoselectivecollapseofpolymerchainsyieldingtadpolelikestructures4Mostcontrolled/livingpolymerizationsarecarriedoutunderhomogeneousconditionstoassurethesamegrowthprobabilityforallchains,andconsequenthighuniformity.However,sometimesheterogeneityandcompartmentalizationcanofferadditionalpossibilitiesofcontrol.TheadvantagesofconductingaCRPinminiemulsioncanbeafasterrateandreducedterminationbychaincoupling.5Hybridsbetweennaturalandsyntheticpolymersformanewclassofbio-conjugates.Theycanbepreparedbeeitherusinganendfunctionalsyntheticpolymerandsubsequentlyextendit,intheformofagraftorblockcopolymer,withanaturalpolymerorbyintroductionofagroupwhichcouldinitiatepolymerizationofasyntheticmonomerintoanaturalpolymer6Copolymerswithsufficientlyregularincompatiblesegmentswillphaseseparateintonanostructuredmorphologies.Minimizationofsurfaceinteractionsleadstothefamiliarspherical,cylindricalandlamellarmorphologies,whichcansometimesbesupplementedbyothermorphologiessuchasgyroidal,perforatedlamellae7Polymermorphologiescanbeadditionallyfixedbycrosslinkingorcalcificationofinorganicsegments.Thus,additionofsilicaprecursorstoblockcopolymersorlowmolarmasssurfactants,canleadtotheformationofsilicawithavarietyofdifferentregularshapesandtomesoporoussilicawithhighcatalyticorseparationactivity.Asimilarapproachwasusedwhenoneofthesegmentsofblockcopolymerswaspolyacrylonitrile