End-group interchain exchange reaction in polymer blends: evolution of the block weight distribution

Abstract

Abstract The kinetics of interchain exchange reactions proceeding via end-group mechanism in homogeneous polymer blends is studied theoretically. A set of kinetic equations describing the evolution of the block weight distribution is derived. It is demonstrated that the process may be divided into a fast and a slow stage. The fast stage is characterized by alteration in the fractions of end sequences of different type. At the same time most of the homopolymer chains transform into copolymer with block weight distribution close to the Flory distribution. In the course of the subsequent slow stage, the distribution shape is preserved, with average block lengths gradually decreasing to the values typical of the completely random copolymer. The copolymer composition is found to change mostly in the course of the fast stage of the process. The possibilities of using kinetic data for the discrimination between end-group and direct interchange mechanisms are discussed.