Rouse Dynamics of Block Copolymers

Abstract

We present rigorous analysis for the dynamic intrachain correlations of block copolymers within the Rouse model, which uncovers current misunderstandings of the dynamics of unentangled block copolymers in solutions and melts. Analytic predictions are made for the dynamic correlations at large and small distances, respectively, providing a critical test for the theory of Benmouna et al. which ignores memory effects and is based on a “dumbbell” model. At large distances, differences exist with regard to the k and composition dependence of the internal mode relaxation time. At small distances, on the other hand, we find non-Markovian stretched exponential decay, as opposed to their Markovian simple exponential decay, and for the correlation between two dynamically asymmetric blocks, a single mode with an intermediate decay constant, in contrast to the linear combination of the two intrablock correlation decay modes obtained by Benmouna et al. Furthermore, for structurally and dynamically symmetric but composition asymmetric diblock copolymers, they do not formally recover their predictions for homopolymers.