DYNAMICS OF BLOCK-COPOLYMER CHAINS NEAR THE MICROPHASE SEPARATION TRANSITION

Dynamical properties of an individual diblock copolymer are investigat ed. A generalized Rouse equation is derived for polymer chains compose d of several blocks differing with respect to their monomeric units. T his equation takes into account explicitly the dynamics of the block c opolymer melt surrounding the probe chain. In general, the structure o f this generalized Rouse equation differs from the corresponding resul ts for a multicomponent homopolymer blend. It is applied to diblock co polymers close to the microphase separation, which is characterized by strong composition fluctuations and the critical slowing down of thei r dynamics. Emphasis is laid on the role of composition fluctuations i n the dynamics of individual diblock chains. A slowing down with respe ct to the center-of-mass motion as well as the internal relaxations is expected. Results for the Gaussian model and the Brazovskii theory ar e compared. They show significant differences.