Cylindrical Nanostructure of Rigid-Rod POSS-Containing Polymethacrylate from a Star-Branched Block Copolymer

A nanostructure consisting of rectangular polyhedral oligomeric silsesquioxane (POSS) nanodomains packed into a hexagonal lattice was observed in POSS-containing A(2)B star-branched polymers. The A(2)B star-branched polymers, which comprised polystyrene (A) and bulky POSS-containing poly(methacrylate) (PMAPOSS) (B) units, were synthesized by anionic polymerization and addition reaction. The self-assembled structures of the A(2)B star-branched polymers were studied via transmission electron microscopy (TEM) and small- and wide-angle X-ray scattering (SAXS and WAXS, respectively). It was found that a rectangular nanostructure was packed into a hexagonal arrangement of nanodomains for a PMAPOSS volume fraction of 40 vol. % in the star-branched polymer. In addition, the cylinder-like nanostructure of bulky POSS observed, which is not observed in the case of PS-b-PMAPOSS diblock copolymers, was formed owing to the curvature effect, which is the result of the branched architecture of the copolymer.