SINGLE-CHAIN DYNAMICS IN A BINARY POLYMER BLEND

The dynamics of an individual chain in a binary polymer blend is inves tigated. A generalized Rouse equation takes into account the coupling to the dynamics of the surrounding polymer matrix. This generalizes Sc hweizer's approach to a multicomponent polymer system. The results are applied to a symmetric binary blend. Emphasis is laid on the role of composition fluctuations, which are strongly enhanced close to the pha se separation and then show critical slowing down. This has an impact on the dynamics of individual chains. As a result of the treatment, th e internal chain motion is expected to be more strongly affected than the center-of-mass motion. A physical interpretation is presented such that the chains are strongly expelled from unfavorable environments. It is discussed how the results are modified if-instead of a mean-fiel d treatment-the theory of critical phenomena is applied to describe co mposition fluctuations.