Synchrotron SAXS Studies on Lattice Structure of Spherical Micelles in Binary Mixtures of Block Copolymers and Homopolymers

Abstract

The lattice structures of spherical micelles in binary mixtures of polybutadiene-poly(ε-caprolactone) diblock copolymers and polybutadiene homopolymers were investigated using synchrotron small angle X-ray scattering technique. In the blend sample with a weight fraction of added homopolymer (φ_homo) of 40 wt%, hexagonally packed cylinders were formed, while spherical morphologies were arrayed into the Frank-Kasper σphase at φ_homo = 50 wt%. Closely packed spheres in hexagonal closely packed (HCP) and face-centered cubic (FCC) lattices were observed for the sample with φ_homo = 56 and 67 wt%, respectively. It was found that the lattices of spherical micelles assembled into the following phases with increasing φ_homo: Frank-Kasper σ, HCP,and FCC phases.