Flow-Induced “Shish-kebab” Formation: A New-Scenario of Kinetic Pathways for􀀁Entangled Polymer Solutions

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• Takeji Hashimoto, Prof. Emeritus, Kyoto University, Kyoto, Japan
• Monday 16 November 2009, 14:00-15:00
• Pippard Lecture Theatre, Cavendish Laboratory.

If you have a question about this talk, please contact Erika Eiser.

This work is concerned with general research themes on open non-equilibrium phenomena in statistical mechanics and materials science, specifically self-assembly of ordered (the so-called dissipative) structures of molecular systems under external flow fields. To elucidate the self-assembly under the external fields is crucial both academically to understand the pattern formation in nature and industrially to create advanced materials of the next generation. The explorations of the phenomena have been recognized to be one of the most important research items in fundamental physical science, materials science and technology, and biological science. This work clarifies for the first time a whole series of kinetic pathways, for concentrated crystallizable polymer solutions subjected to shear and extensional flows, which leads to formation of intriguing, complicated, but fundamental “shish-kebab” crystalline superstructures. The shish-kebabs, which have been applied to various important industrial products such as ultrahigh-strength fibers, were first reported by Pennings et al in 1965. Since then its formation mechanism has been extensively and intensively investigated, as one of the most important and fundamental research themes in polymer science by a great number of researchers based upon a concept of the flow-induced crystallization phenomenon. Nevertheless the mechanism has not been fully clarified yet. Here we show that the mechanism involves not only the flow-induced crystallization but also the flow-induced phase separation, at least in the case of polymer solutions, and that intricate couplings between the two phase transitions (crystallization and phase separation) are crucial for a more profound understanding of the mechanism. We present a new scenario for a series of kinetic pathways on shish-kebab formation in polymer solutions.

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