MECHANISMS OF CHAIN DIFFUSION IN LAMELLAR BLOCK-COPOLYMERS

We report measurements of chain diffusion in macroscopically oriented, well-entangled lamellar block copolymers. Diffusion in the lamellar p lane is proposed to occur by an ''activated reptation'' mechanism when the composition profile is roughly sinusoidal. At higher degrees of s egregation a crossover to an entropically limited ''block retraction'' mechanism is apparent. Diffusion through the layers reflects a thermo dynamic barrier determined by the combination of temperature and molec ular weight.