Phase behavior of multi-arm star-shaped polystyrene-\textit{block}-poly(methyl methacrylate) copolymer

We synthesized star-shaped polystyrene-\textit{block}-poly(methyl methacrylate) copolymer (PS-$b$-PMMA) by utilizing $\alpha $-cyclodextrin ($\alpha $-CD) as a core of the star-shaped block copolymer. Eighteen hydroxyl groups on $\alpha $-CD were transformed to bromine by the reaction with $\alpha $-bromoisobutyryl bromide. We found that the number of bromine substituted arms per one $\alpha $-CD was higher than 16, which was determined by nuclear magnetic resonance and Matrix-assisted laser desorption/ionization. We could control molecular weight of block copolymers by changing polymerization times. The block copolymers were characterized by gel permeation chromatography and nuclear magnetic resonance. Phase behaviors of these star-shaped block copolymers were investigated by small angle X-ray scattering and transmission electron microscopy.