SURFACE-INDUCED ORDERING IN BLOCK-COPOLYMER MELTS

Surface-induced ordering in block copolymer melts is studied numerically. For symmetric copolymers, the thickness of the surface-enrichment layer is found to scale as R(eq)similar to N-theta With theta approximate to 0.6, suggesting the system is undergoing a surface-induced strong segregation. The density profile perpendicular to the interacting surface is described quite well by the form predicted by Fredrickson in a mean-field analysis. In asymmetric copolymers, the surface is found to have a profound effect on domain formation. For some off-critical compositions? domains were found to form near the surface with a geometry different from that in the bulk; while for stronger asymmetry in composition, minority domains were nucleated near the wall only, long before any formed in the bulk. These interesting pattern formation processes should be observable in experiments using a depth profiling technique.