Thin-Film Morphologies of Random Copolymers as Functions of Thermal History

Series polymers of butyl methacrylate with various contents of 3-(trimethoxysilyl)propyl methacrylate (MSMA) that introduces crosslinking networks among the macromolecules upon hydrolysis and self-condensation have been synthesized by free radical polymerization, and the influence of crosslinking density on the film properties has been examined. The polymer solutions were spin-cast over a layer of polystyrene brush to yield homogeneous polymer films. When the films of about 30 nm thick were exposed to moisture and then heated at 60 degrees C for hydrolysis and self-condensation of MSMA groups, the initially flat surfaces became slightly coarser but without apparent dewetting. Further annealing at 140 degrees C resulted in dewetting of the thin films, whose morphologies in thermodynamic equilibrium were related to the chemical compositions of the polymers. The polymers having higher contents of MSMA exhibited significantly reduced dewetting at the high temperature, due to the higher density of crosslinking networks that restricted the molecular mobility. In contrast to the thin films of about 30 nm thick, thicker films (about 100 nm) showed only a slight dewetting, even non-dewetting at the elevated temperature. Copyright 2001 Academic Press.