高分子相变中的亚稳态行为科学的应用进展.ppt

metastablestatesinphasetransitionsofpolymers 高分子相变中的亚稳态行为 姓名 王孟导师 陈大俊学号 108215 outline 1 conceptsofmetastablestates2 metastablestatesinsingle componentsystem3 metastablestatesinpolymerblendsystem4 metastablestatesinpolymer solvent nonsolventsystem5 conclusion equilibriumandstabilityinclassicalmechanics a anunstableequilibrium b astableequilibrium c arandomequilibrium and d adouble well whichincludesoneunstableequilibriumpointsurroundedbytwostableequilibriumpoints twofilleddotsrepresentthelimitofstability 1 conceptsofmetastablestates stableequilibriumandmetastability metastablestate g equilibriumstate asametastablestate itisstablewithrespecttoinfinitelysmallperturbations butitmaynotbestablewithrespecttolimitedperturbations overcomethefreeenergybarrier g towardsastableequilibriumstate g atransformationfromonestablestatetoanotherstablestatewillproceedthroughsuccessivestagesofmetastablephaseswheneversuchametastablestateexists phenomenologically ametastablestatemayexistduetoitsfastkineticpathwayeventhroughthisstateisthermodynamicallylessstablethantheequilibriumstate ostwald stephenz d cheng condensedstatesinpolymericmaterials includingtransitionthermodynamics kinetics molecularmotioninmetastablestates crystalstructureandmorphology liquidcrystalpolymers 2 metastablestatesinsingle componentsystem peo nififtransition cheng s z d et al macromolecule 1997 29 311 327 gibbs thomson stephenz d cheng 2007 448 1006 1008 pe crystalstylestransition c h m weber et al nanolett 2007 7 7 2024 2029 enantiotropicandmonotropicphasebehaviors enantiotropicphasebehavior monotropicphasebehavior g td ti melt l c crystal g ti tm melt l c crystal oneexampleofmonotropicbehaviorinpolymers tangetal chem mater vol 13 no 1 2001 hobt c8 dsccoolingcurvesofhobt c8 dscheatingcurves singlephase idealequilibriumtwomacroscopicphases inpracticalcasedispersionphase metastablephase 3 metastablestatesinpolymerblendsystem 0 dg q q b1 b2 xb2 xb1 misciblemixtureofaandb dg 0 b1 b2 xb2 xb1 s1 s2 phaseseparatedmixtureofaandb binodalspinodal twophase metastableregion ucstphasediagram one stepphaseseparation two stepphaseseparation z wangetal polymer 2005 46 2675 2684 x h zhang etal macromolecules vol 39 no 21 2006 bp berghman spoint atbp phaseatconcentratedsideoftheline vitrifies t g t bp concentrationofpolymer tgbecomesindependentofconcentration andphasemorphologyisfrozenin liquid liquidphaseseparationwithvitrification liquid liquidphaseseparationwithcrystallization crystallization tm t concentrationofpolymer c a b a b m2 m1 m3 m4 invariantline phasemorphologyofm1 phase crystalmorphologyofm3 oneexampleofliquid liquidphaseseparationwithcrystallization x h zhang et al rapidcommun 2005 26 1285 fluctuation assistedcrystallization schematicallydiagramofliquid liquidofpolymer solvent nosovent 4 metastablestatesinpolymer solvent nonsolvent thecompositionpathschematicallydiagramofthetopofcastingfilmduringtheimmersionprecipitationprocess c y kuoetal journalofmembranescience315 2008 187 194 a phasediagramofbuoh dcm plla b processofporousfibersformation z qietal materialsletters 2008 inpress 国内外碳纤维质量的差异 不是完全凝胶化 真正凝胶化 transientstatesinpolymerphasetransformations identificationsofphaseinpolymercrystalpolymorphism monotropicliquidcrystall