Transition behavior of PS- b-PMMA films on the balanced interfacial interactions

Abstract

The thickness dependence of the order-to-disorder transition (ODT), measured by in situ grazing-incidence small-angle X-ray scattering (GISAXS), has been investigated in thin films of a symmetric polystyrene- b-poly(methyl methacrylate) (PS- b-PMMA) on a random copolymer (P(S- r-MMA)) grafted to the substrate where the interfacial interactions are balanced. With decreasing film thickness less than 25 L 0, the ODT significantly decreases to 193 °C for film of 10 L 0 in thickness, because the interfacial interactions by a random copolymer grafted to the substrate provide a surface-induced compatibilization toward two block components. However, a plateau of the ODT at ∼213 °C for films thicker than 25 L 0 was observed above the bulk value of 200 °C. The elevation of this ODT indicates a suppression of compositional fluctuations normal to the film surface, more than likely because the dominant orientation of the lamellar microdomains was found to be parallel to the film surface.