Metastable States in Phase Transitions of Polymers高分子相变中的亚稳态行为高分子相变中的亚稳态行为姓姓 名名: 王王 孟孟导导 师师: 陈大俊陈大俊学学 号号: 108215Outline1. Concepts of Metastable states 2. 2. Metastable states in single-component systemin single-component system3. 3. Metastable states in polymer blend systemin polymer blend system4. 4. Metastable states in polymer-solvent-in polymer-solvent-nonsolventnonsolvent systemsystem5. 5. ConclusionEquilibrium and stability in classical mechanicsEquilibrium and stability in classical mechanics(A) an unstable equilibrium; (B) a stable equilibrium; (C) a random equilibrium; and (D) a double-well, which includes one unstable equilibrium point surrounded by two stable equilibrium points. Two filled dots represent the limit of stability.1. Concepts of Metastable statesStable equilibrium and metastabilityStable equilibrium and metastability Metastablestate GEquilibriumstateAs a metastable state, it is stable with respect to infinitely small perturbations , but it may not be stable with respect to limited perturbations (overcome the free energy barrier G) towards a stable equilibrium state.GA transformation from one stable state to another stable state will proceed through successive stages of metastable phases whenever such a metastable state exists. Phenomenologically, a metastable state may exist due to its fast kinetic pathway even through this state is thermodynamically less stable than the equilibrium state.OstwaldStephen Z. D. ChengCondensed states in polymeric materials:including transition thermodynamics, kinetics, molecular motion in metastable states, crystal structure and morphology, liquid crystal polymers 2. Metastable states in single-component systemin single-component systemPEO: NIF IF transition Cheng, S. Z. D.et,al. Macromolecule, ,1997,29:311327.GibbsThomson: Stephen Z. D. Cheng, 2007, 448:1006-1008. PE: crystal styles transition C. H. M. Weber,et.al. Nano Lett., 2007 , 7 (7):2024-2029EnantiotropicEnantiotropic and and monotropicmonotropic phase behaviors phase behaviorsEnantiotropic Phase BehaviorMonotropic Phase BehaviorGTdTiMeltL. C.CrystalGTiTmMeltL. C.CrystalOne example of One example of monotropicmonotropic behavior in polymers behavior in polymersTang et al.Chem. Mater., Vol. 13, No. 1, 2001HOBT-C8 DSC cooling curves of HOBT-C8 DSC heating curves Single PhaseIdeal equilibriumtwo macroscopic phasesIn practical casedispersion phase(Metastable phase)3. Metastable states in polymer blend systemin polymer blend system0 GQ*QB1B2XB2XB1Miscible Mixture of A and B G0B1B2XB2XB1S1S2Phase separated mixture of A and BBinodalSpinodalTwo PhaseMetastableRegionUCST phase diagramOne-step phase separation Two-step phase separation Z. Wang et al. Polymer，2005，46 ：26752684 X.H. Zhang,et al. Macromolecules, Vol. 39, No. 21, 2006BP: Berghmans Point At BP, phase at concentrated side of the linevitrifies.Tg T BP Concentration of Polymer Tg becomes independent of concentration, and phase morphology is frozen in.Liquid-liquid phase separation Liquid-liquid phase separation with vitrification with vitrificationLiquidliquid phase separation Liquidliquid phase separation with crystallizationwith crystallizationCrystallizationTmTConcentration of PolymerC*A*B*ABM2M1M3M4Invariant LinePhase morphology of M1:Phase + crystal morphology of M3:One example of liquid-liquid phase One example of liquid-liquid phase separation with crystallization separation with crystallizationX. H. Zhang.et,al. Rapid Commun. 2005, 26, 1285Fluctuation-Assisted Crystallizationschematically diagram of liquid-liquid of polymer-solvent-nosovent4. Metastable states in polymer-solvent-in polymer-solvent-nonsolventnonsolventThe composition path schematically diagram of the top of casting film during the immersion precipitation process.C.-Y. Kuo et al. / Journal of Membrane Science 315 (2008) 187194(a) Phase diagram of BuOH/DCM/PLLA. (b) Process of porous fibers formationZ. Qi et al. / Materials Letters ,(2008) ,in press进一步凝固进一步凝固国内外碳纤维质量的差异国内外碳纤维质量的差异不是完全凝胶化不是完全凝胶化H20 H20 H20 H20 H20 H20 H20 真正凝胶化真正凝胶化 Transient states in polymer phase transformations; Identifications of phase in polymer crystal polymorphism; Monotropic liquid crystalline polymers; Metastable supra-molecular structures and self- assembled systems in polymer blends and copolymers; External field-induced metastability; 5. ConclusionThanks for Your Attention!