Crystal structures of α and β forms of poly(tetramethylene succinate)
Crystal structures of α and β forms of poly(tetramethylene succinate)
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DOI：
10.1016/s0032-3861(99)00659-x
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发表时间：
2000-06-01
期刊：
影响因子：
4.6
通讯作者：
Washiyama, J
中科院分区：
文献类型：
--
作者：
Ichikawa, Y;Kondo, H;Washiyama, J
通过X射线衍射分析了聚丁二酸丁二醇酯（PTMS）的α和β改性的晶体结构：施加应力后出现β形式。这两种变体都属于单斜晶系，空间群为P2（1）/n。在这两种情况下，晶胞包括两个化学重复单元。对于α型，晶胞尺寸为a = 0.523 nm，B = 0.912 nm，c（纤维轴）= 1.090 nm，β = 123.9度;对于β型，a = 0.584 nm，B = 0.832 nm，c（纤维轴）= 1.186 nm，β = 131.6度。这两种晶型的纤维周期的差异主要归因于四亚甲基单元的构象差异，即OR晶型的TGT（G）超过T条，而β晶型的TTTTT。还发现，在PTMS中，由α形式的固有体积相对于真实体积的比率定义的填充系数K几乎等于β形式的填充系数K。这一观察结果可以与聚对苯二甲酸丁二醇酯（PBT）中获得的结果形成对比，其中α形式的K远大于β形式的K。PTMS和PET之间的差异归因于这些聚合物的α和β形式的晶胞体积之间的差异。(C)2000爱思唯尔科技有限公司版权所有。
Crystal structures of the alpha and beta modifications of poly(tetramethylene succinate) (PTMS) were analyzed by X-ray diffraction: the beta form appeared with an application of stress. These two modifications belonged to the monoclinic system with the space group of P2(1)/n. In both cases, a unit cell included two chemical repeating units. For the alpha form, the cell dimensions were a = 0.523 nm, b = 0.912 nm, c (fiber axis)= 1.090 nm, and beta = 123.9 degrees; for the beta form, a = 0.584 nm, b = 0.832 nm, c (fiber axis)= 1.186 nm, and beta = 131.6 degrees. The difference in the fiber periods of the two crystalline forms was attributed mainly to the conformational difference in the tetramethylene unit, i.e. TGT (G) over bar T of the or form and TTTTT of the beta form. It was also found that in PTMS, the packing coefficient, K, which was defined by the ratio of the intrinsic volume with respect to the true volume of the alpha form was almost equal to that of the beta form. This observation could be contrasted to those obtained in poly(butylene terephthalate) (PBT), where the K of the alpha form was considerably greater than that of the beta form. The difference between PTMS and PET was attributed to the difference between the unit cell volumes of the alpha and beta forms of these polymers. (C) 2000 Elsevier Science Ltd. All rights reserved.