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Complexity in Polymer Phase Transitions ---from Materials Science to Life Sciences

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 2008-05-20, Beijing. What are polymers?. Chain-like macromolecules containing 1000 atoms or more.

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Complexity in Polymer Phase Transitions ---from Materials Science to Life Sciences

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  1. 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 2008-05-20, Beijing

  2. 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

  3. 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 • ……

  4. Two basic phase transitions in polymer materials • Liquid-liquid phase separation • Polymer crystallization

  5. Liquid-liquid phase separation • High-impact polystyrene (rubber-plastic blend) AFM picture by Jiang Liu Soft & tough+Hard & crispHard & tough

  6. Polymer crystallization • Semi-crystalline contexture (solid+elastic) Hard & tough Hu, et al. Macromolecules 2003

  7. Fibers Plastics Semi-crystalline Celluloses Starches Chitosan

  8. Polymers belong to complex fluid • Complexity: 32 definitions (Wikipedia) “Integration larger than addition.”

  9. Polymers belong to complex fluid • Complexity: integration larger than addition. “1+1>2”

  10. Complexity in polymer phase transitions L-L phase separation + Crystallization  Their interplay

  11. Phase diagrams of polymer solutions L-S crystallization Interplay L-L L-S Competition and even more!

  12. Molecular driving forces T L-L L-S Polymer concentration Drive Drive Mixing interactions B New energy parameter! Classic Flory-Huggins parameter Flory J. Chem. Phys. 1942. Huggins Ann. N.Y. Acad. Sci. 1942. ？

  13. Why do we need new parameter? • Phase diagrams in a single component

  14. Molecular packing In a single component Gas  Liquid  Solid CondensationCrystallization In polymer solutions Dilute  Concentrated  Crystalline Liquid-Liquid demixingCrystallization Packing energy: first stage L-L demixing second stage L-S crystallization

  15. Molecular driving forces T L-L L-S Polymer concentration Drive Drive Mixing interactions B Parallel-packing interactions Ep Classic Flory-Huggins parameter Flory J. Chem. Phys. 1942. Huggins Ann. N.Y. Acad. Sci. 1942. New energy parameter! Hu J. Chem. Phys. 2000.

  16. Partition function for polymer solutions Coordination number q,volume n,solvent takes n1sites,n2polymer chains, each taking r sites. Hu J. Chem. Phys.113, 3901(2000); Hu et al. 118, 10343(2003).

  17. Verify mean-field theory with simulations • 32-mers at T(Ep/Ec, B/Ec) Theoretical predictions Simulation verifications L-L L-S Hu, W.-B.; Mathot, V.B.F; Frenkel, D. J. Chem. Phys.118, 10343(2003).

  18. The first story--- Crystal nucleation enhanced by L-L demixing.

  19. Crystallization influenced by L-L demixing 1st L-S coexistence L-L binodal 2nd 3rd Control the crystal morphology! Hu, W.-B.; Frenkel, D. Macromolecules 37, 4336(2004)

  20. Onset temperatures of crystal nucleation on cooling 128-mers in solutions C1：B/Ec=0.076,Ep/Ec=1 C2：B/Ec=0.03,Ep/Ec=1.072 C3：B/Ec=-0.1,Ep/Ec=1.275 Lines: crystal nucleation Dashes: L-L binodal Dots: L-L spinodal Crystal nucleation triggered by spinodal decomposition！ Zha, L.-Y.; Hu, W.-B. J. Phys. Chem. B 111, 11373-11378(2007).

  21. Modulate morphology at low temperatures Triggered by prior SD No prior SD Zha, L.-Y.; Hu, W.-B. J. Phys. Chem. B 111, 11373-11378(2007).

  22. Crystal nucleation enhanced at the interfaces of incompatible polymers 16-mers 50:50 blends, EP/EC=1, variable B/EC, kT/EC=4.0. Ma, Y.; Zha, L.-Y.; Hu, W.-B.; Reiter G.; Han, C. C. Phys. Rev. Ein press.

  23. Theoretical interpretation L-S phase diagrams for variable B/Ec L-S Ma, Y.; Zha, L.-Y.; Hu, W.-B.; Reiter G.; Han, C. C. Phys. Rev. Ein press.

  24. Something different in polymer solutions 128-mers，50%，Ep/Ec=1,variable B/Ec, kT/Ec=4.5 Manuscript under preparation.

  25. Crystal nucleation enhanced at surfaces only with very poor solvent L-S phase diagrams for variable B/Ec Manuscript under preparation.

  26. The second story--- L-L demixing enhanced by crystallizability.

  27. L-L demixing among isotactic, atactic and syndiotactic polypropylenes Mixing free energy of polymer blends: >0 ~0 for similar chemistry ~0 for r1,r2>>1 Component-selective crystallizability drives L-L demixing! Hu, W.-B.; Mathot, V.B.F. J. Chem. Phys. 119, 10953(2003).

  28. L-L demixing enhanced by fluctuations towards crystalline order Mean-field treatment Fluctuations? L-L 32-mers in 323 lattice Ep/Ec=1, variable B/Ec Data points: simulations Lines: L-L binodals Dashes: L-S coexistence L-S Ma, Y.; Hu, W.-B.; Wang, H. Phys. Rev. E 76, 031801(2007).

  29. The third story--- Single-chain folding accelerated by collapse transition.

  30. Classification of polymer solutions Critical overlapping concentration C* Dilute solutions C<C*，Concentrated solutions C>C*

  31. Phase diagrams in single-chain systems Single 512-mer with variable B/Ep Collapse transition Tcol Crystallization Tcry Hu, W.-B.; Frenkel, D. J. Phys.Chem. B 110, 3734-7(2006)

  32. Free energy calculation at equilibrium T Height of free-energy barrier

  33. Crystal nucleation enhanced by prior collapse transition Hu, W.-B.; Frenkel, D. J. Phys.Chem. B 110, 3734-7(2006)

  34. Protein folding Levinthal paradox: It is formidable for protein folding to experience all possible conformation. The folding must have a fast path. Beta folding is a crystal nucleation process!

  35. 1.Framework model via nucleation 1+2=Nucleation-condensation model 2.Hydrophobic molten globule as intermediate

  36. Fast path of protein folding

  37. Physics origin of life • Life is a non-equilibrium phenomenon evolved in nature for dissipating energy more efficiently.

  38. Physics origin of life • Life emerges at the edge of phase transitions with their interplay. The interplay provides adaptability and efficiency to bio-functions, for instance, the fast path of protein folding. • Chain-like macromolecules are favorable for performing interplay.

  39. Summary • Complexity in polymer phase transitions is represented by their interplay： 1、L-L demixing enhances crystal nucleation and thus modulates crystal morphology； 2、Sometimes crystallizability enhances L-L demixing； • Fast path of protein folding may be based on this kind of interplay.

  40. Thanks for your attentions！ Discussions are welcome!

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