Polymorphism of Syndiotactic Poly(m-methylstyrene)

Abstract

The synthesis and a preliminary structural characterization of syndiotactic poly(m-methylstyrene) are reported. A complex polymorphic behavior has been revealed. Three different polymorphic forms and two clathrate structures, characterized by the inclusion of guest molecules in the crystalline lattice, have been found. The conditions for the obtaining of the various polymorphic forms, in unoriented and. oriented fiber samples, are described. Form I, obtained by crystallization from the melt or from the amorphous phase, is characterized by chains in the s(2/1)2 helical conformation. The same helical conformation has been found in the clathrate structures containing molecules of o-dichlorobenzene or benzene. Form II can be obtained by crystallization from solutions of solvents which do not form clathrate structure or by removing the guest molecules from the clathrate forms. Form III, obtained in oriented fibers by stretching amorphous films, is a mesomorphic modification characterized by chains in the trans-planar conformation with a high degree of disorder in the lateral packing of the chains. Annealing treatments or solvent-induced crystallization of the oriented mesomorphic form allow the obtaining of oriented fibers in some of the polymorphic forms. The differences and analogies with the polymorphic behavior of syndiotactic poystyrene and poy(p-methylstyrene) are outlined

Determination of the Crystal Structure of Syndiotactic 3,4‐Poly(2‐methyl‐1,3‐butadiene) by Molecular Mechanics and X‐Ray Diffraction

“…The chains of syndiotactic vinyl polymers in the crystalline state assume the most common low energy conformations characterized by sequences of torsion angles in the backbone of the kind TTTT or TG ± G ± T (with the pairs G ± G ± comprising a CH 2 group). Chain conformations with both sequences of torsion angles have been found for various syndiotactic vinyl polymers 12–22. As a consequence, conformational polymorphism is quite common for this class of polymers.…”

Effect of Methoxy Side Groups on the Crystal Structures of a Series of Syndiotactic Polymethoxystyrenes as Studied by the X-ray Diffraction Data Analysis

“…It is expected immediately that the chain conformation, chain packing mode, and the resultant physicochemical property may be affected remarkably depending on their positions. The effect of the side groups on the structure of SPS has been reported in the several papers, including the CH 3 , − halogen, , and n -butyl groups . However, there had been no study to investigate systematically the role of one particular side groups substituted at the different positions of the phenyl groups of the SPS polymer.…”

Chain Conformation, Crystal Structures, and Structural Disorder in Stereoregular Polymers

“…199 Mesomorphic forms characterized by conformationally ordered polymer chains packed in lattices with different kinds of lateral disorder have been described for various isotactic and syndiotactic polymers. For instance, for iPP, 200 sPP, 201 sPS, 202 syndiotactic poly(p-methylstyrene) (sPPMS), 203 and syndiotactic poly(m-methylstyrene), 204 mesomorphic forms have been found. In all of these cases the X-ray fiber diffraction patterns show diffraction confined in well-defined layer lines, indicating order in the conformation of the chains, but broad reflections and diffuse haloes on the equator and on the other layer lines, indicating the presence of disorder in the arrangement of the chain axes as well as the absence of long-range lateral correlations between the chains.…”