Guest Occupation Effects on the Transition of Crystalline Syndiotactic Polystyrene: Selection Criteria for Fundamental Structures γ ‐I and γ ‐II

Abstract

Molecular dynamics simulations are performed on clathrate forms of crystalline syndiotactic polystyrene containing toluene, chloroform, and carbon dioxide, to investigate the effects of guests on thermally induced structural transitions. Two crystalline forms, γ ‐I and γ ‐II, are produced. γ ‐I is obtained from crystals with lower guest occupation ratios, while γ ‐II is obtained from crystals with higher ratios. The b‐length of the crystal unit cell of the γ ‐II form is twice of that of the γ ‐I form; the other lattice parameters are almost identical. Based on a hypothesis that the experimentally observed γ form is a mixture of the γ ‐I and γ ‐II forms, X‐ray diffraction patterns for film samples with uniplanar orientations are reasonably interpreted. The thermodynamically stable form is γ ‐I, although the γ ‐II form is preferentially produced in the presence of guest molecules.