The optical‐configuration parameter for ethene‐propene copolymers

Abstract

Rotational isomeric state theory is used to predict values of the optical-configuration parameter Aa for ethene-propene copolymers as a function of chemical composition, chemical sequence distribution, and stereochemical structure of the propylene sequences. The calculations are based on information available for ethene and propene homopolymers, and on the model used to interpret the unperturbed dimensions of these copolymers. Values of Aa were generally found to decrease significantly with increase in the fraction of propylene units, but to be relatively insensitive to chemical sequence distribution and stereochemical structure. The extent of their agreement with experiment is consistent with comparisons previously reported for a variety of homopolymers. It is intermediate to the poor agreement generally obtained for symmetric chains (such as polyethylene) and the satisfactory agreement generally obtained for asymmetric chains (such as polypropylene).