Multimolecule glasses and crystals of isotactic polystyrene |
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| Authors: | Haishan Bu Jie Cao Shengyoung Xu Ze Zheng Bernhard Wunderlich |
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| Institution: | 1. Department of Material Sciences , Fudan University , Shanghai, 200433, People's Republic of China;2. Beijing Laboratory of Electron Microscopy , Chinese Academy of Sciences , Beijing, 100080, People's Republic of China;3. Department of Chemistry , University of Tennessee , Knoxville, TN, 37996-1600;4. Chemical and Analytical Sciences Division , Oak Ridge National Laboratory , Oak Ridge, TN, 37831-6197 |
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| Abstract: | When spreading dilute solutions of isotactic polystyrene (iPS) on water, it was observed that different concentrations produce different morphologies in the resulting amorphous films. From 10?1 to 10?2 wt% solutions, ribbonlike films and circular platelets of multimolecule aggregates were obtained. After isothermal crystallization of these amorphous films, lamellae, incipient spherulites, and single-molecule crystals were observed. The formation of lamellar crystals lying flat on the substrate is an indication of the absence of epitaxy by the substrate, which would require the molecular chains to be in the surface plane and thus yield lamellae normal to the substrate. The dense packing in the center of sheaflike spherulites is caused by screw-dislocation growth, and it produces structures similar to shish kebabs. It was also observed that the lamellae grown from the center develop secondary growth spirals, causing the branching and splaying of the structure typical for spherulitic growth. |
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