高分子物理chapter5CondensedStatesofPolymers高分子的聚合状态

5.2PolymerCrystallizationRequisitesforpolymercrystallization

Chemicalregularity

Homopolymer

Copolymer blockcopolymer randomcopolymer

Stereoregularity(立构规整度)

Isotactic(等规)

Syndiotactic(间规)

Atactic(无规)5.2.1ChainConformationsinCrystals21314161525142=2162=

31717273929183813231H31HelixConformationsZig-zagConformationsH21HydrogenbondingsyndiotacticisotacticrepeatingunitWhyHelix?HH0.25nmPE0.12nmPPCH3:0.2nm

ChainpackingincrystallatticesLHRHLHLHLHLHRHRHRH

ChainpackingincrystallatticesPEorthorhombictriclinicHydrogenbondingTrigonali-Poly-1-buteneMonoclinic5.2.2BasicMorphologyofPolymerCrystals

CrystalHabits:

a:lamellar

(薄片状)b:platyc:tabulard:isometrice:prismaticf:acicularg:needle-like

h:fibrous

(纤维状)“Singlecrystals”

haveonelatticeMacromolecularcrystalsareoftenlamellarorfibrous.“Polycrystallinesamples”areaggregatesofmanysinglecrystalsLamellaeCrystallizedfromDiluteSolution

Polyethylene(聚乙烯)Tc~70CTc~80COrientationsofpolymerchainsinlamellaePEchainsmustbefoldedbackandforthwithinthelamella!Note:thelamellarthicknessis~10nm,thechainlengthis>1000nm.PEchainsareperpendiculartothelamellarsurface.

Polyoxymethylene(聚甲醛)PEO(聚氧乙烯)-b-PS(聚苯乙烯)diblockcopolymerLamellaeCrystallizedfromMelt

Spherulites(球晶)ofpolymersUnderPolarizedopticalmicroscopy

LamellaeinaspheruliteLamellaeTieMoleculesAmorphousThemechanismof

MaltesecrossextinctionpatternOP:PolarizerOA:AnalyzerQE:VectorofpolarizedlightI0projectingonOATheoreticalanalysisof

MaltesecrossextinctionpatternprojectingonOARelationsofPOMandSALS(smallanglelightscattering)POMSALSSALSpatternsofspherulitesVvHvqmax~1/R5.2.3PolymerCrystallizationHowdothepolymerchainspackinthelamellarcrystals?Randomcoilwiththechaincontourlength(轮廓长度)longerthan1mmLamellawiththethicknessof5-50nmandlateralsizeofmicrons.Crystallization

Macroconformations(巨构象):Extendedchains(伸展链)Foldedchains(折叠链)Randomcoils(无规线团)Fringedmicelle(缨状微束)Chain-FoldedLamellaeofPolymersRandomcoilCrystallizationTCorDT

Chainfolding(链折叠)conceptChain-foldedLamellaeseFoldedchain(折叠链)Foldsurface(折叠表面)sLateralsurface(侧表面)TC:crystallizationtemperature(结晶温度)DT:supercooling(过冷度),DT=Tm0-TC

se:foldsurfacefreeenergy(折叠表面自由能)s:lateralsurfacefreeenergy(侧表面自由能),se10slLamellarthicknessorfoldlength(片晶厚度)ProcessofPolymerCrystallization

Twosteps:

1.Nucleation(成核)processSizeDG0embryosupercritic.sizestablecriticalnucleusDG=Gcrystal–Gmelt,DG=DH–TDSGcrystal=Gbulk+SAsDG=Gbulk-Gmelt

+SAs

=DGf+SAsA

isthesufaceareaand

DGfisthe

bulkfreeenergychange.abcSchematicrepresentationofthechangeinfreeenergyasafunctionofsizeillustratingthenucleationprocessTypesofcrystalnuclei.(a)primary(初次),(b)secondary(二次),(c)tertiary(三次)nucleus.

Homogeneous(均相)andheterogeneous(异相)nucleationEstimatethecriticalnucleussize

Forprimarynucleus

Forsecondarynucleus2.LinearGrowthofPolymerCrystallizationTemperaturedependenceoflineargrowthrate(线生长速度)Temperaturedependenceoftheradialgrowthrateuofspherulitesinisotacticpolystyrene(left),polyamid6(center)andpoly(tetramethl-p-silpheylenesiloxane)(right).Tf:equilibriummeltingtemperature.SurfacenucleationonsubstratewithlengthLwitharateiLineargrowthrateG:thegrowthrateofcrystalperpendiculartothesubstratel:foldlength;a:widthofstem;b:thicknessofthestem;g:substratecompletionrateOverallPolymerCrystallizationRateOverallcrystallizationrate(总结晶速度)Tm0TgTMAXOverallrate‘Bell’curveofoverallcrystallizationratewc:weightfraction;vc:volumefractionW:weights:density(g/cm3):specificvolume(cm3/g)＝1/

Definitionofcrystallinity(结晶度)wc

Wc/Wtotal;vcVc/VtotalTimeCrystallinityIsothermalcrystallizationT1T2T3t1/2IIIIIIIVOverallCrystallizationKineticsAvramiequationh0h¥1/2tt1/2lnththt’Dilatometric(膨胀计法)Kineticsmodelsofoverallcrystallization1.FreegrowthmodelR~vtb.newnucleusproduced-

homogeneousa.constantnumbersofnucleus-

heterogeneoust+DttDttI*nucleationratetPoisson’sraindropproblemIfraindropsfallrandomlyonapondcreatingexpandingcircularwaves,whatisthechancethatthenumberofwavescreatedbydifferentraindropswhichpassoverarepresentativepointPuptotimetisexactlyn?Kineticsmodelsofoverallcrystallization-Avrami2.ImpingementmodelPPoissondistributionWhatisthechancethatnowavereachesagivenpointPinspace?heterogeneoushomogeneousTheAvramiequationfor3DE(t):wavespreadingareaduringtWhiletorvisverysmallorThermodynamicsofCrystallization:

1.MeltingpointofLamellarCrystalsThermodynamicsofCrystallization:

1.MeltingpointofLamellarCrystalsMeltingdataforlamellarpolyethylenegrownfromthemeltandfromsolutionTm=414.2(1-0.627/l)Lauritzen-HoffmanequationSimilartocriticalnucleussizeGibbs-ThomsonextrapolationlaThermodynamicsofCrystallization:

2.MeltingpointofPolymermixtureChemicalPotentialofPolymerinamorphousphaseConsiderasystemofPolymer/Impuritymixture:ChemicalPotentialofonemonomerunitofpolymerinamorphousphasePolymeriscompatiblewithimpuritybutcan’tco-crystallizewithimpurityEffectsof“Impurities”onTmConditionofPhaseEquilibriumSuperscriptofC:CrystallinePhaseSuperscriptofI:AmorphousPhaseEffectsof“Impurities”onTmForx2,x1=1Forend-groupeffects:1=2/N,=0Forcopolymeralternatingcopolymer:P<<XARandomcopolmer:P=XABlockCopolymer:P>>XA1P:ProbabilityofcrystallineunitwithsequentialconnectionNote:Forpolymerblendspolymer/smallmoleculepolymer/polymer3.EffectsofChainStructureonTm1)SymmetryandAsymmetry2)FlexibleandRigid3)MolecularInteraction5.3OrientedStatesofPolymersDefinition

ApplicationsFiber,BOPP,BOPET,BOPE,…Orientationfunctionq<cosq><cos2q>fullyorientedfullydisorder10perpendicular011/30F10-1/2q:0~180°oneortwodimensionalorder5.4LiquidCrystallinePolymers“Liquidcrystalsstandbetweentheisotropicliquidphaseandthestronglyorganizedsolidstate.Lifestandsbetweencompletedisorder,whichisdeath,andcompleterigidity,whichisdeathagain.”

DervichianD.G.Mol.Cryst.Liq.Cryst.

1977,40,19.

Statesofmatter:Solids,liquids,andgases“Liquidcrystals”(LCs)representanumberofdifferentstatesofmatterinwhichthedegreeofmolecularorderliesintermediatebetweentheperfectlong-rangepositionalandorientationalorderfoundincrystallinesolidandthestatisticallong-rangedisorderfoundinanisotropicliquid.Phenomenologically,LCsexhibitbothsolid-likeanisotropicfeaturesandliquid-likefluidity.Onthebasisofthesecharacteristics,theterm“mesomorphicphases”or“mesophases”,maybeamoreappropriatenamethanliquidcrystals.WhatareLiquidCrystalsAnisotropicmolecularshapeofliquidcrystalsRod-likeorellipsoid-likeSpacefillingmodelofmolecule7S5Plate-likeordisk-like

Lyotropicliquidcrystals(溶致型液晶):Theliquidcrystalphaseisdependentontheconcentrationofonecomponentinanother.

Thermotropicliquidcrystals(热致型液晶):Theliquidcrystalphasesofpuresubstancearecausedbytemperaturechange.NematicPhase(向列相)DirectorNLong-rangeorientationalorderofmoleculesMoleculesNnnnnnnn

MoleculararrangementinanematicphasePolydomainstructureinanematicphase.Localdirectorsarerepresentedbyn,andtheglobaldirectorisrepresentedbyN.SmecticPhases(近晶相)DirectorNLayersMolecules

LayerstructureinsmecticphasesSmecticASmecticCTiltAngleDirectorNLayersMoleculesLiquidCrystalPhaseofChiralMoleculesStructureofchiralsmecticorsmecticC*phase.Theplanesrepresentthesmecticlayers.Thedirectoralwaysmakesthesameanglewiththesmecticplanes,buttheorientationofthedirectorrotatesaboutthelineperpendiculartotheplanesingoingfromonelayertothenext.Cholestericphase(胆甾相)(chiral(手性)nematicphase)

Chiral

smecticphaseMoleculesinthecholestericphase.Thedirectornrotatesinahelicalfashion.Becausenophysicalquantitiesdependonthesignofn,thephysicalpitchofthecholestericphaseisP=p/k0ratherthan2p/k0.Cholesterolnonanoatemolecule:Lyotropicliquidcrystals:

1)surfactantsoramphiphilicblockcopolymersLyotropicliquidcrystals:

2)rigid-rodpolymershCc2*~M-1c1*c2*c1*~M-2POMUsedintheStudyofLCPhasesFordifferentLCphases,thetextures(织构)underPOMaredifferentNematic: