Late stages of ordering of thin polymer films on chemically heterogeneous substrates: energetics and metastability

By a direct numerical integration of the dynamical evolution equations, we study phase separation of thin polymer blend films in two-dimensional models. The focus of our work is on the late-time morphology of the films. We first investigate morphological transitions in a thin film on a flat, homogeneous substrate. In particular, we probe the transition between a completely wetting and a partially wetting surface morphology. This transition is controlled by a competition between surface interactions and the interfacial energy in a thin film. This competition becomes even more pronounced when a chemically patterned substrate is used. For films cast on a patterned substrate, we consider several different substrate pattern widths and surface interaction strengths in our simulations. We also probe effects of thermal fluctuations on the late-time film morphology by carrying out simulations to many different final quench temperatures. Along with quench simulations, we further study film morphology by slow cooling the film from an initial high temperature. Comparing the morphology of films for a quench case to a slow-cooling case, we identify possible barriers to reaching equilibrium in experimental situations under a quench. (C) 2001 Published by Elsevier Science Ltd.