DIRECT IMAGING OF SURFACE AND BULK STRUCTURES IN SOLVENT-CAST POLYMERBLEND FILMS

We have used laser confocal fluorescent microscopy and atomic force mi croscopy to study surface and bulk morphologies in solvent cast poly(m ethyl methacrylate) (PMMA)/polystyrene (PS) films. The solvent evapora tion rate strongly affects the surface morphology. Sufficient suppress ion of solvent evaporation results in a periodic distribution of highl y monodisperse PMMA-rich domains. Formation of the surface pattern is interpreted in terms of diffusion-driven coarsening of the minor phase and flow induced by the diffusive transport of PMMA molecules from th e bulk of the liquid film to the air-film interface.