Craze fibril extension ratio measurements in glassy block copolymers

The extension ratios of crazes in triblock copolymer films of poly(2-vinylpyridine)-polystyrene-poly(2-vinylpyridine) [PVP-PS-PVP] which had lamellar microphase domain structure were measured by transmission electron microscopy. The extension ratio when the lamellae were oriented parallel to the craze fibril direction was always greater than that when the lamellae were oriented perpendicular to this direction, reflecting the stretching of the chains of the block copolymer in a direction normal to the interfaces of the lamellar domains. © 1992 Steinkopff-Verlag.