Morphological and scattering studies of binary mixtures of block copolymers; Cosurfactant effects observed in the parameter space of temperature, blend composition, and molecular weight ratio

Franois, C.*; Yamaguchi, Daisuke; Hashimoto, Takeji

Thermoreversible order-order transitions between various morphologies occurring on binary mixtures of diblock copolymers were investigated by using small-angle X-ray scattering. The complex morphological behaviors observed here can be understood on the basis of two key features of the binary blends: the co-surfactant effect and the possibility for the chemical junctions of the shorter diblock to migrate away from the interface as segregation power decreases. As a summary of this series of studies, a three-dimensional phase diagram was constructed in the parameter space of overall volume fraction of polystyrene block in the mixture, the ratio of the degree of polymerization of long asymmetric diblock chain to that of short symmetric diblock chain and temperature. Such a phase diagram illustrates that the cosurfactant effect opens perspectives in tailoring morphologies of self-assembled, nano-structured materials.