Phase separation and surface morphology of spin-coated films of polyetherimide/polycaprolactone immiscible polymer blends

The surface morphology in thin films of immiscible polyetherimide and polycaprolactone blends was studied using scanning electron and atomic force microscopy. The thin films were obtained by spin-coating from dichloromethane solution. A self-assembled periodic pattern of phase separated domains was observed, which was induced by capillary effects along with the solution radial flow and the unsteady air flow field above the film during the initial stages of spin-coating. A secondary phase separation was observed during the solvent evaporation stage of spin-coating. The differences in surface topographies of the two distinct phases are attributed to different solvent evaporation rates within each phase. In addition, a great variety of domain structures and surface morphologies were observed as a function of polymer blend composition.