Abstract— The effect of polymethyl methacrylate (PMMA) block length on the surface morphology of the two block copolymers (BCPs) was investigated by AFM using tapping mode. Two asymmetric polystyrene block polymethyl methacrylate (PS-b-PMMA) copolymers with different PMMA block lengths were synthesized by a novel combination technique; living anionic polymerization and hydroboration autoxidtion reactions. The molar mass of PS block was (MW PS = 90000 g/mol) and the molar mass of PMMA blocks were (MW PMMA =130000 and MW PMMA =180000 g/mol). Thin films of two asymmetric copolymers were prepared by solvent casting (10 mg/5 ml THF) on freshly cleaved mica. The results showed that phase separation do occur and equilibrium morphologies were observed. It was found that BCP with PMMA molar mass (MW PMMA =130000 g/mol) form parallel cylinders (stripes) oriented horizontally to the substrate. While BCP with PMMA molar mass (MW PMMA =180000 g/mol) form hexagonal ordered cylindrical oriented perpendicular and parallel to the substrate.
Keywords— AFM, block copolymer, phase separation, polystyrene block polymethyl methacrylate, surface morphology.