Conformational Analysis of Poly(methylene-1,3-cyclopentylene) and Chain Conformation in the Crystalline Phase
Conformational Analysis of Poly(methylene-1,3-cyclopentylene) and Chain Conformation in the Crystalline Phase
复制标题
聚(亚甲基-1,3-亚环戊基)的构象分析和晶相中的链构象
DOI：
--
复制
发表时间：
1995
期刊：
影响因子：
--
通讯作者：
G. Guerra
中科院分区：
文献类型：
--
作者：
O. R. Ballesteros;L. Cavallo;F. Auriemma;G. Guerra
对不同微观结构的聚亚甲基-1，3-环戊烷(PMCP)进行了构象分析。与PMCP的微观结构无关，适合于无序晶相的扩展构象在几何和能量上都是可行的。然而，需要对环和主链的构象自由进行严格的限制。PMCP样品的实验衍射图与孤立PMCP延伸链的傅里叶变换计算结果的相似性证实了PMCP的晶相由平行的延伸链(构型和构象无序)组成，链轴呈伪六角排列，但沿链轴几乎完全是分子间的旋转和平移无序。熔融熵随所考察的各种构象有序(顺式、反式或全同立式)的增加，可能是由于无序晶相中相应的较高的构象顺序所致。
A conformational analysis for poly(methylene-1,3-cyclopentane) (PMCP) for different microstructures is presented. Independently of the microstructure of PMCP, extended conformations suitable for the disordered crystalline phase are geometrically and energetically feasible. However, strong restrictions to the conformational freedom, both of the rings and of the backbone, are required. The similarity between the experimental diffraction profiles of a PMCP sample and the Fourier transform calculations for isolated PMCP extended chains confirms that the crystalline phase of PMCP consists of parallel extended chains (configurationally and conformationally disordered) with a pseudohexagonal arrangement of the chain axes but with a nearly complete intermolecular rotational and translational disorder along the chain axes. The large increases of the entropy of melting with all the examined kinds of configurational order (cis or trans or isotactic) would be due to the related higher conformational order in the disordered crystalline phase.