Surface restructuring of polystyrene/polymethacrylate blends in water studied by atomic force microscopy

Blends of poly(n-butyl methacrylate) (PBMA)/polystyrene (PS) and poly(n-octyl methacrylate) (POMA)/PS were imaged with atomic force microscopy in both ambient and aqueous environments. The surfaces of the blends were monitored over time under water, and most PBMA/PS and POMA/PS samples showed no surface restructuring. A morphology change, however, was observed for high ratios of POMA and specific ratios of PBMA in the blend. For the blend of 60% PBMA and 40% PS, the surface was pitted in air with depths of 60 nm. In water, as the exposure time increased, islands replaced the holes on the surface. The height of these islands averaged 50 nm. At high ratios of POMA, in POMA/PS blends, the surface structure also changed when contacted with water. The structural changes that were observed for all of these select blends were reversible after the surface was dried and reimaged in air. Sum frequency generation vibrational spectroscopy was used to give insight into the functional groups and surface chemical composition of the blends in air and water.