Domain Structures on PS-PMMA Mixture Films

We studied the domain structures in immiscible polystyrene- poly(methyl methacrylate) (PS/PMMA) lms by using atomic force microscopy, lateral force microscopy and force spec-troscopy. As previously known, circular PS bumps are formed on the PMMA layer after annealing, which was conrmed by the topographic image. We found that lateral force image showed sub-structures on the PS bumps. The sub-structures (or domains) have circular shapes on the centers of the PS bumps. Because the lateral forces on the domains have similar values on the PMMA layer, the domains are thought to have the chemical composition of PMMA. This estimate is supported by the force spectroscopy result, which shows that the pull-o force between the domain and a cantilever tip also has values similar to that for the PMMA layer