Conformational properties of poly(alkene sulphone)s in solution: 2. A rotational isomeric state study of the poly(cyclohexene sulphone) chain

Abstract

The rotational isomeric states model, coupled with the Flory matrix method, was applied to the calculation of the unperturbed mean-square end-to-end distance in poly(cyclohexene sulphone) as a function of several parameters. The calculations were performed for atactic, isotactic and syndiotactic chains; the tacticity arises from the two possible ways, D and L, in which the rings can be attached to the main chain, assuming that the CC bonds are all in the t conformation, as indicated by dielectric measurements. One of the three conformations about each CS bond is strongly hindered and was given zero statistical weight whereas the other two were assigned weights determined by second-order effects, operating over three or more consecutive bonds, and dependent on the chirality of the rings and the coulombic interactions between adjacent dipoles. The calculations for the atactic model, in which a Monte Carlo procedure was used to generate the chain, were found to agree with experiment only if the parameter α was given a value of 5 or greater. This parameter is determined by the relative orientation of successive sulphone dipoles and was expected to have a value less than unity. It appears that specific solvation effects help to stabilize ( t, g) and ( g, t) CSC bond pairs relative to t, t. Other parameters are not so important. The calculations for the isotactic and syndiotactic models show interesting features, particularly for certain limiting conditions when cyclic or helical structures are generated. For these models there is a greater sensitivity to the various parameters than in the atactic case.