Synthesis and Phase Behavior of PS-(PS-b-P2VP)₃ Miktoarm Star Block Copolymer

Gyroid nanostructures have received much attention because of potential applications for next-generation storage devices and membranes. However, to maximize its structural advantages, gyroid nanostructures with larger channel volumes are needed.

In this study, we synthesized polystyrene-[polystyrene-b-poly(2-vinylpyridine)]₃ miktoarm star block copolymer [PS_L-(PS_S-b-P2VP)₃] where PS_L and PS_S are long and short PS chains, respectively. We changed the volume fraction of the PS block (f_PS) and the chain asymmetry of the PS chain [τ = f_PS,L/(f_PS,L+f_PS,S)]. When both f_PS and τ are large (f_PS = 0.81, τ = 0.79), highly asymmetric lamellar structure is observed. Interestingly, when the f_PS becomes smaller (f_PS = 0.64), gyroid structure is preferred at large τ (τ = 0.65), but lamellar structure is formed with decreasing τ (τ = 0.46). The experimental results are consistent with the predictions based on self-consistent field theory (SCFT).