Creation of multi-scale stripe-like patterns in thin polymer blend films

Multiscale polymeric patterns resulting from flow on an inclined substrate of a binary polymer blend solution of polystyrene and poly-n-butylacrylate in toluene are analyzed with sub-microbeam GISAXS and real space techniques. The locally isotropic phase-separation structure on the 1 micron scale, including a molecular substructure, is embedded in a superstructure on the 100 micron scale of stripe-like variations of film thickness and composition oriented perpendicular to the flow direction. It is argued that the multiscale pattern results from the interplay of evaporation, convective flow, differential diffusion and spinodal decomposition.