高分子相变中的亚稳态行为科学的应用进展

1、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: 108215 outline 1. concepts of metastable states 2. 2. metastable states 3. 3. metastable states 4. 4. metastable states 5. 5. conclusion (a) an unstable equilibrium; (b) a stable equilibrium

2、; (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 states metastable state g equilibrium state as a metastable state, it is stable wi

3、th 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. g a transformation from one stable state to another stable state will proceed through successive stages of metastable

4、 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. ostwald stephen z. d. cheng condensed states in polymeric materials: including transi

5、tion thermodynamics, kinetics, molecular motion in metastable states, crystal structure and morphology, liquid crystal polymers 2. metastable states peo: nif if transition cheng, s. z. d.et,al. macromolecule, ,1997,29:311327. ) 2 1 ( 0 hl tt e mm gibbsthomson: ) 2 1 ( 0 hl tt e mm stephen z. d. chen

6、g, 2007, 448:1006-1008. . pe: crystal styles transition c. h. m. weber,et.al. nano lett., 2007 , 7 (7):2024-2029 enantiotropic phase behaviormonotropic phase behavior g tdti melt l. c. crystal g titm melt l. c. crystal tang et al.chem. mater., vol. 13, no. 1, 2001 hobt-c8 dsc cooling curves of hobt-

7、c8 dsc heating curves single phase ideal equilibrium two macroscopic phases in practical case dispersion phase (metastable phase) 3. metastable states 0 g q* q b1 b2 xb2xb1 miscible mixture of a and b g 0 b1 b2 xb2 xb1 s1 s2 phase separated mixture of a and b binodal spinodal two phase metastable re

8、gion b c ucst phase diagram one-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, 2006 bp: berghmans point at bp, phase at concentrated side of the line vitrifies. tg t bp concentration of polymer tg becomes in

9、dependent of concentration, and phase morphology is frozen in. crystallization tm t concentration of polymer c* a*b* ab m2 m1m3 m4 invariant line phase morphology of m1: phase + crystal morphology of m3: x. h. zhang.et,al. rapid commun. 2005, 26, 1285 fluctuation-assisted crystallization schematical

10、ly diagram of liquid-liquid of polymer-solvent-nosovent 4. metastable states the 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) proc

11、ess of porous fibers formation z. 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; meta