New structural motif in hexagonally ordered cylindrical ternary (ABC) block copolymer microdomains

The morphologies of a polystyrene-block-polybutadiene-block-poly(methyl methacrylate) triblock copolymer (SBM) with polybutadiene as the majority component as they are cast from different solvents and solvent mixtures are determined using transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) techniques. Besides a lamellar morphology and microphase separated structures of poor long-range order, a morphology is identified in which both A (polystyrene, PS) and C (poly(methyl methacrylate), PMMA) chains form separate cylindrical microdomains. In contrast to the square (p4mm) symmetry for the cylinder arrangement which has been discussed in the case of ABC triblock copolymers with B being the matrix forming component, we now report the formation of a new morphological motif of hexagonal (p6mm) symmetry, where A and C form two kinds of cylindrical microdomains in a B matrix.