Crazing in polystyrene-polybutadiene diblock copolymers containing cylindrical polybutadiene domains

Polystyrene-polybutadiene diblock copolymers exhibiting morphologies of cylindrical rubbery domains in a glassy matrix were studied in tensile stress-strain experiments. The various contributions of rubber volume fraction, overall copolymer molecular weight, and blending of diblock copolymers with homopolymers were examined. Transmission electron microscopy revealed a novel internal structure of the crazes in certain samples; inspection of the micrographs of these crazes suggests that the craze matter forms by a two-step process: cavitation in the rubbery domains followed by necking and drawing of the topologically continuous polystyrene matrix.