PMSE 74 |
| Simultaneous measurements of wide-angle and small-angle X-ray scatterings have revealed an intimate relationship between the structural change in crystal lattice and the change in morphological change or lamellar stacking structure in the phase transition phenomena of crystalline polymers. When the structure change occurs in the crystal lattice, the molecular conformation and the packing mode of chains change remarkably. At the same time the long period and lamellar thickness change drastically. This morphological change is caused by the enhancement of thermal motion of molecular chains, especially the translational motion along the chain axis coupled with the trans-gauche conformational exchange, as supported by molecular dynamics calculations. Some examples are shown concretely: (1) Ferroelectric phase transition of vinylidene fluoride-trifluoroethylene copolymers, (2) Brill transition of aliphatic nylons and the newly discovered phase transition occurring immediately below the melting point, and (3) complicated phase transitions of syndiotactic polystyrene between the δ, γ and α forms. |
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50 Years after the Discovery of Polymer Single Crystals: A Look Back, Current Discoveries and Future Opportunities
1:30 PM-5:15 PM, Sunday, August 19, 2007 Westin Boston Waterfront -- Alcott, Oral
Division of Polymeric Materials: Science & Engineering |