Surface segregation in the minority component of the binary polymer mixture

According to a common viewpoint the surface of the binary polymer mixture A/B could be enriched only in one component, say A, regardless of the value of its bulk volume fraction phi(bulk). From recent theoretical analyses and Monte Carlo simulations one can expect however that some mixtures can exhibit surface segregation in the minority blend component, i.e. enrichment in the component A for phi(bulk) < 50% and in the component B for phi(bulk) > 50%- Using composition-depth profiling techniques, we have observed both types of the segregation with only one- or both-blend component(s) preferred at the surface. These results were obtained for model mixtures composed of partly deuterated (dx) and protonated (hx) random olefinic copolymers of the structure -[C4H8](1-x)[C2H3(C2H5)](x)-. A simple mean-field model is presented to explain both situations. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.