高分子相变的复杂性---从材料到生命
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Two basic phase transitions in polymer materials
• Liquid-liquid phase separation • Polymer crystallization
Liquid-liquid phase separation
• High-impact polystyrene (rubber-plastic blend)
Partition function for polymer solutions
n n1 n n2 q n2 ( r 2) n2 ( r 1) n2 ( r 1) n2 rn2 Z ( ) ( ) ( ) zc e zp zm n1 n2 2
Coordination number q,volume n,solvent takes n1 sites,n2 polymer chains, each taking r sites.
Molecular driving forces
T
L-L
L-S
Drive
Polymer concentration
Drive
Mixing interactions B Parallel-packing interactions Ep Classic Flory-Huggins parameter New energy parameter! Flory J. Chem. Phys. 1942. Hu J. Chem. Phys. 2000. Huggins Ann. N.Y. Acad. Sci. 1942.
Polymer concentration
Drive
Mixing interactions B Classic Flory-Huggins parameter Flory J. Chem. Phys. 1942. Huggins Ann. N.Y. Acad. Sci. 1942.
New energy parameter!
Their interplay
Phase diagrams of polymer solutions
L-S crystallization
Interplay
L-L
L-S
Competition and even more!
Molecular driving forces
T
L-L
L-S
Drive
2008-05-20, Beijing
What are polymers?
• Chain-like macromolecules containing 1000 atoms or more. ---1953 Nobel Laureate H. Stäudinger
http://www.chemistryexplained.com/St-Te/Staudinger-Hermann.html
Age of polymer materials
• • • • • • • • Plastics (include foam plastics, thin films) Rubbers (tires, shoes, seals) Fibers (clothes, textures) Coatings (oil painting) Adhesives Water-absorbing and filtering resins Artificial organs ……
Polymers belong to complex fluid
• Complexity: integration larger than addition. “1+1>2”
Complexity in polymer phase transitions
L-L phase separation + Crystallization
AFM picture by Jiang Liu
Soft & tough+Hard & crispHard & tough
Polymer crystallization
• Semi-crystalline contexture (solid+elastic)
Hard & tough
Hu, et al. Macromolecules 2003
Complexity in Polymer Phase Transitions
---from Materials Science to Life Sciences
Wenbing Hu (胡文兵) School of Chem. and Chem. Eng. Nanjing University CHINA
In polymer solutions Dilute Concentrated Crystalline Liquid-Liquid demixing Crystallization
Packing energy: first stage L-L demixing second stage L-S crystallization
zp e
q 2 ( r 1) n 2 E p [1 ] 2 nq / 2 kT
Hu J. Chem. Phys. 113, 3901(2000); Hu et al. 118, 10343( 2003).
Hale Waihona Puke Baidu
?
Why do we need new parameter?
• Phase diagrams in a single component
Molecular packing
In a single component Gas Liquid Solid Condensation Crystallization
Plastics
Semi-crystalline
Fibers
Celluloses
Starches
Chitosan
Polymers belong to complex fluid
• Complexity: 32 definitions (Wikipedia) “Integration larger than addition.”