hydrogen-bonding-in-polymer-blends

Hydrogen-bondinginpolymerblendsShiao-WeiKuoReceived:6December2007/Accepted:14March2008/Publishedonline:1May2008#SpringerScience+BusinessMediaB.V.2008AbstractHydrogenbondinginpolymerblendsisatopicofgreatinteresttopolymerscientistsbecausesuchsystemshavemanypotentialapplications.Introducingfunctionalgroupstoonecomponenttomakeitcapableofforminghydrogenbondstoanother,therebyenhancingthemisci-bilityofotherwiseimmiscibleblends,isoneofthemajorachievementsduringthepast20yearsofpolymerscience.ThePainter–Colemanassociationmodelgenerallydescribestheseinteractionsaccurately.ThisReviewdiscussesindetailtheeffectsofhydrogenbondingonthemiscibilityandthermalpropertiesofpolymerblendsystems.KeywordsHydrogenbonds.Polymerblends.Miscibility.Glasstransitiontemperature.Meltingtemperature.CrystallizationNomenclatureAFMAtomicforcemicroscopyPHBPoly(3-hydroxybutyrate)ACAVinylalcohol-co-vinylacetatePHEMAPoly(hydroxylethylmethacraylte)BPABisphenolAPHPMAPoly(hydroxylpropylmethacrylate)CHEXCyclohexanePHSPoly(hydroxystryene)DMADynamicmechanicanalysisPLLAPoly(l-lactide)DMFDimethylformamidePMAPoly(methylacrylate)DSCDifferentialscanningcalorimetryPMAAMPoly(methylmethacrylamide)EMAAEthylene-co-methacrylicacidPMMAPoly(methylmethacrylate)IPPIsopropylphenolPPzMAPoly(phenylmethacrylate)LiClO4LithiumperchloratePPOPoly(dimethylphenyleneoxide)NMRNuclearmagneticresonancePSPoly(styrene)PAAPoly(acrylicacid)PSOHPoly(styrene-co-vinylphenol)PASPoly(acetoxystyrene)PVAPoly(vinylalcohol)PBMAPoly(butylmethacrylate)PVAcPoly(vinylacetate)PBTPoly(butyleneterephathlate)PVCPoly(vinylchloride)PBzMAPoly(benzylmethacrylate)PVDFPoly(vinylidenefloride)PCHMAPoly(cyclohexylmethacrylate)PVPPoly(vinylpyrrolidone)PCLPoly(ɛ-caprolactone)P2VPPoly(2-vinylpyridine)PDAPoly(adipicester)P4VPPoly(4-vinylpyridine)PDMSPoly(dimethylsiloxane)PVPhPoly(vinylphenol)PECHPoly(epichlorohydrin)SAAStyrene-co-acrylicacidPEDEKPoly(etherdiphnyletherketone)TEMTransmissionelectronmicroscopyPEEKPoly(etheretherketone)THFTetrahydrofuranJPolymRes(2008)15:459–486DOI10.1007/s10965-008-9192-4S.-W.Kuo(*)DepartmentofMaterialsScienceandOptoelectronicEngineering,CenterforNanoscienceandNanotechnology,NationalSunYat-SenUniversity,Kaohsiung804,Taiwane-mail:[e-mail](ethylmethacrylate)XPSX-rayphotoelectronspectroscopyPEOPoly(ethyleneoxide)PEOxPoly(2-ethyl-2-oxazoline)IntroductionInrecentyears,muchattentionhasbeenpaidtothenatureofhydrogenbondsandtheireffectsonthemicrostructuresandphysicalpropertiesofvariousmateri-als[1–6].Theclassicalexampleiswater.Itisnowgeneralrecognizedthatthetetrahedralwaterclusterconsistsof14watermolecules,thecentral10ofwhichformastrongclusterandtheremainingfourformpentagonsinthecompletedicosahedralcluster.Theunusualpropertiesofwaterarisefromtheabilityofwatermoleculestoformhydrogenbondswithvariousmoleculesandions—anddoingsoinatetrahedralgeometry[7].OtherexamplesofhydrogenbondingsystemsinmolecularbiologyarethehybridizationofDNAduplexes[8]andtheα-helixandβ-sheetsecondarystructuresofpolypeptides,whicharestabilizedthroughintramolecularandintermolecularhydro-genbonds,respectively[9,10].Ingeneral,hydrogenbondinghasaprofoundeffectonthephysicalpropertiesofpolymermaterials,includingtheirmeltingtemperature,glasstransitiontemperature,dielectricconstant,surfaceproperties,andcrystalstructure,aswellasthecentralconcernofthisreview:thesolubilityandmiscibilityofpolymerblends.Polymerblendingisapowerfulroutetowardmaterialsexhibitingpropertyandcostperformancessuperiortothoseoftheirindividualcomponents.Inessence,threetypesofblendscanbedistinguished:completelymiscible,partiallymiscible,andimmiscible[11,12].Inmostcases,polymerblendsareimmisciblebecauseofthehighdegreesofpolymerizationoftheircomponents;thus,theentropytermbecomesvanishinglysmallandthemiscibilitybecomesincreasinglydependentonthenatureofcontributionoftheenthalpicterm.Toenhancetheformationofsingle-phase,misciblepolymerblends,itisnecessarytoensurethatfavorablespecificintermolecularinteractionsexistbetweenthetwobasecomponentsoftheblend.Ideally,onepolymerwillpossessdonorsitesonitschain;theother,acceptorsites.Themostcommonlyobservedinteractionsaregenerallyacid/basetypes,namelyhydrogenbonding,ion-dipole,π–π,orchargetransferinteractions[13–19].Muchofourresearchinrecentyearshasinvolvedstudiesofintermolecularhydrogenbonding.Although,severalexcellentreviewsexistonhydrogen-bondedpoly-merblends[20–26],thisreviewmainlydiscussesourrecentresearcheffortsinthisfield.CharacterizationofhydrogenbondHydrogenbondTheconceptofthehydrogenbondbeingadirected,attractiveinteractionbetweenanelectron-deficienthydro-genatomandaregionofhighelectrondensityhasbeenreviewedthoroughlyinseveralbooks[27]andreviews[28].Ingeneral,ahydrogenbondisdefinedasasysteminwhichahydrogenatomliesbetweentwoatomsAandB—ideallyinthelinearformA–H···B—withthedistancebetweenthenucleiofAandBbeingconsiderablyshorterthanthesumofthevanderWaalsradiiofAandBandthediameteroftheproton(i.e.,theformationofahydrogenbondleadstocontractionoftheA–H···Bsystem).TheatomsAandBareusuallyhighlyelectronegative,s