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 model s. The focus of our work is on the late-time morphology of the films. We fi rst investigate morphological transitions in a thin film on a flat, homogen eous substrate. In particular, we probe the transition between a completely wetting and a partially wetting surface morphology. This transition is con trolled by a competition between surface interactions and the interfacial e nergy in a thin film. This competition becomes even more pronounced when a chemically patterned substrate is used. For films cast on a patterned subst rate, we consider several different substrate pattern widths and surface in teraction strengths in our simulations. We also probe effects of thermal fl uctuations 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 hig h temperature. Comparing the morphology of films for a quench case to a slo w-cooling case, we identify possible barriers to reaching equilibrium in ex perimental situations under a quench. (C) 2001 Published by Elsevier Scienc e Ltd.