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

Ordering of spherical particles represents a fundamental topic in materials science and engineering ranging from the sub-nanometer scale packing of atoms in simple crystals to micron sized assemblies of colloids. Graduate students Sangwoo Lee and Michael Bluemle, working with Frank Bates, recently discovered a fascinating new packing symmetry for sphere-forming block copolymer melts referred to as a Frank-Kasper sigma-phase, characterized by a gigantic tetragonal unit cell containing 30 discrete self-assembled microdomains per lattice point.