Determination of the crystal structure of poly-(p-phenylene terephthalate) from power diffraction data. A computer modelling approach
Determination of the crystal structure of poly-(p-phenylene terephthalate) from power diffraction data. A computer modelling approach
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根据功率衍射数据测定聚对苯二甲酸乙二醇酯的晶体结构。
DOI：
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发表时间：
1995
期刊：
影响因子：
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通讯作者：
A. Windle
中科院分区：
文献类型：
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作者：
S. Hanna;P. Coulter;A. Windle
用分子模拟和X射线粉末衍射相结合的方法测定了聚对苯二甲酸对苯二醇酯的晶体结构。在25℃时，聚合物的晶胞参数为a=7.98A，b=5.33A，c=12.65A，β=98.98°。用于预测结构的方法由几个不同的阶段组成。最初，组装了与聚合物的组成单元相关的结构信息数据库。分子模拟程序被用来构建和操纵基于这些信息的模型晶体，并使用能量计算来丢弃那些在能量上不可能的或在空间上不可能的。最后，对其余模型的粉末衍射图进行了模拟，并与实验数据进行了比较。然后，对晶体结构的可能候选者进行迭代精炼，以提高模拟和实验之间的一致性。该方法特别适用于解决聚合物的结构，如目前的情况，不能形成大的单晶或取向纤维。
The crystal structure of poly-(p-phenylene terephthalate), PPT, has been determined using a combination of molecular modelling and X-ray powder diffraction. The polymer is found to crystallize in the monoclinic space group, P21/a, with unit-cell parameters a= 7.98 A, b= 5.33 A, c= 12.65 A and β= 98.98 ° at 25 °C. The crystal packing favours intermolecular phenyl-edge to phenyl-face and carbonyl-carbon to carbonyl-oxygen interactions over other possibilities. The method used to predict the structure consisted of several distinct stages. Initially, a database of structural information relevant to the component units of the polymer was assembled. A molecular modelling program was used to construct and manipulate model crystals based on this information and energy calculations employed to discard those which were energetically unlikely, or sterically impossible. Finally, powder diffraction patterns were simulated for the remaining models and compared with experimental data. Likely candidates for the crystal structure were then iteratively refined, to improve the agreement between simulation and experiment. The method is particularly useful for solving structures of polymers which, as in the present case, are unable to form large single crystals or oriented fibres.