Face-Centered Cubic Lattice of Spherical Micelles in Block Copolymer/Homopolymer Blends

Abstract

Spherical micelles of block copolymers may arrange into macrolattices in the bulk, in the blends with homopolymers, and in the solutions with low molecular weight solvents. In this study, we present the first experimental observation on the face-centered cubic (fcc) lattice of spherical micelles in diblock copolymer/homopolymer blends based on the blend of a symmetric poly(ethylene oxide)-block-poly(1,4-butadiene) (PEO-b-PB) and a PB homopolymer. The fcc lattice at elevated temperatures is verified through small-angle X-ray scattering and transmission electron microscopy. The thermally induced phase transition on heating is found to proceed through an order−order transition from body-centered cubic (bcc) to fcc phase followed by an order−disorder transition from fcc packing to disordered micelles and eventually to a homogeneous melt with only thermal concentration fluctuations.