Thin block copolymer films : film formation and corrugation under the AFM tip

The tip of an atomic force microscope was used to induce nanoscale ordering in thin films of polystyrene-poly(4-vinyl pyridine) block copolymers under low force. The AFM tip produces rims on a mesoscopic scale oriented perpendicularly to the scanning direction. A wide range of molecular weights of both blocks was investigated and it was found that after two scans and at constant polymer length there is a linear relationship between the fraction of polystyrene in the polymer and the average separation between two successive rims. Scanning the area in between two rims showed that there is no polymer left on the surface. This is an indication that the mobility of the poly(4-vinylpyridine) anchor blocks is high during sliding of the tip. Different methods for the preparation of the thin polymer films were investigated. A scaling model for diblock copolymer adsorption was used to interpret the results.