Monte Carlo simulation of polymer mixtures: recent progress

The phase diagram of symmetrical polymer blends (A, B) confined into thin f ilms is studied, considering both the effect of finite film thickness D and of surface forces at the confining walls that either prefer both the same species, or different species. In the case of "neutral" walls confinement e nhances the compatibility of the blend. The critical temperature is depress ed, the coexistence curve gets flattened (reflecting a crossover from 3-dim ensional to 2-dimensional critical behavior). But if both walls preferentia lly attract species A, then also the critical composition of the blend is s hifted to the A-rich side of the phase diagram, and the coexistence curve e xhibits a bulge just above the wetting transition temperature. If one wail attracts A and the other B, lateral phase separation sets in via a first or der transition. Above this transition, an interface parallel to the walls i s stabilized in the system.