Frank-Kasper-like network phase from self-assembly of high-χ star-block copolymers.

By taking advantage of the effects of solvent selectivity and topology on high-χ block copolymer (BCP) for self-assembly, network phases with high packing frustration can be formed in self-assembled polystyrene--polydimethylsiloxane (PS--PDMS). Apart from gyroid with trigonal structure and diamond with tetrahedral structure, a peculiar network phase with space group of [Formula: see text] (Frank-Kasper structure) can be found in six-arm star-block PS--PDMS as evidenced by small-angle x-ray scattering. Electron tomography results reveal the network phase with alternating connection of three and four struts. The observed phase behaviors suggest that the network formation is built from the bisectors of dispersive spheres in the Frank-Kasper phase, instead of building connections among them, and thus decipher the origins of complex phase formation due to the adaptive character of malleable mesoatoms.