Morphology and mechanical properties of poly(dimethyl siloxane-b-styrene-b-dimethyl siloxane) block copolymers

The films of poly(dimethyl siloxane-b-styrene-b-dimethyl siloxane) block copolymers cast from different solvents showed significant changes in both the phase morphology and the tensile behaviour. Methyl ethyl ketone and tetrahydrofuran gave hard films and appear to have a continuous polystyrene phase. Conversely cyclohexane, a good solvent for polydimethyl siloxane segment gave softer more elastic films. Intrinsic viscosity data of block copolymers of varying siloxane content showed highest value in toluene and least in cyclohexane which is a theta solvent for polystyrene segment. The tensile properties are also influenced by thermal ageing of films at 100 and 150°C.