Metastable isotactic polystyrene prepared by freeze-extracting concentrated solutions in solvents of middle molecular size
Metastable isotactic polystyrene prepared by freeze-extracting concentrated solutions in solvents of middle molecular size
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DOI：
10.1021/ma034230k
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发表时间：
2003-05
期刊：
影响因子：
5.5
通讯作者：
Dongshan Zhou;Liang Li;Yuqin Li;Jun Zhang;G. Xue
中科院分区：
文献类型：
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作者：
Dongshan Zhou;Liang Li;Yuqin Li;Jun Zhang;G. Xue
通过广角 X 射线衍射、红外光谱和差示扫描量热法对从中分子尺寸溶剂中的浓缩溶液中冷冻提取的等规聚苯乙烯 (iPS) 的形态和结晶行为进行了表征。研究发现，冷冻提取的 iPS 样品结晶度较差，但链呈有序的 31 螺旋构象，加热后很容易转变为高度结晶状态。即使从熔体中冷却也很容易结晶。即使在 520 K 熔化后仍能保持有序的 31 螺旋结构，该结构比熔点高 30 K，但在 530 K 时减弱。从中等尺寸溶剂中的浓缩溶液中冷冻提取的样品的亚稳态特性可归因于较少的链间缠结，就像苯中非常稀的溶液中的集体颗粒的行为一样。
The morphology and crystallization behavior of freeze-extracted isotactic polystyrene (iPS) derived from concentrated solutions in solvents of middle molecular size were characterized by the wide-angle X-ray diffraction, infrared spectroscopy, and differential scanning calorimetry. It was found that the freeze-extracted iPS sample is poorly crystallized, but the chains are in an ordered 31 helix conformation, which can be easily transferred to a highly crystalline state upon heating. It can easily crystallize even cooled from the melt. The ordered 31 helix structure could be maintained even after melting at 520 K, which is 30 K higher than the melting point, but diminished at 530 K. The metastable property of the freeze-extracted sample from concentrated solutions in solvent of middle size can be attributed to fewer interchain entanglements, like the behavior of collective particles from very dilute solution in benzene.