Discovery of a Frank-Kasper σ Phase in Sphere-Forming Block Copolymer Melts

Abstract

Block Copolymer Assembly Despite their structural simplicity, block copolymers can assemble into complex and often surprising structures. Lee et al. (p. 349 ; see the Perspective by Peterca and Percec ) demonstrate the formation of a new ordered phase in a diblock copolymer and a tetrablock copolymer formed from frustrated self-assembled spherical microdomains. Remarkably, this structure contains tetragonal unit cells with 30 spheres per lattice site and is related to dodecagonal quasicrystals. This structure was first described by Frank and Kasper as a sigma phase 50 years ago and is seen in some metal alloys.