AFM study of phase-separated morphology in immiscible blend thin films

Phase-separation behavior of polystyrene (PS) and poly(methyl methacrylate) (PMMA) 1:1 blend film has been studied as a function of film thickness and component by adding PS-b-PMMA diblock copolymer. After annealing, PS is phase-separated into circular-shaped bumps on a PMMA layer. The bump number is inversely proportional to the film thickness in log-log plot while the slope is invariable for the blends with and without 5% PS-b-PMMA diblock copolymer. The bump size and inter-bump spacing are also affected by both the film thickness and addition of the block copolymer.