Solvent Effects in Styrene—Butadiene—Styrene Block Copolymer Cast Films and Evidence for Supermolecular Ordering by X-Ray and Light Scattering

It has been found that solution-cast films of an SBS block copolymer (Kraton 1101) have two orders of phase structure. The first is of molecular dimension and consists of elongated polystyrene domains (≈ 200 A˚) dispersed in a polybutadiene matrix. There is also a supermolecular heterogeneous structure of spherical domains of fractional micron size. A somewhat larger nearest neighbor distance is also seen. The domain size and separation are larger for the polymers cast from solvents for polystyrene than those cast from a solvent for polybutadiene alone. Furthermore, SBS films cast from good solvents for polystyrene exhibit additional supermolecular ordering in contrast to the more random arrangement of the others.