Dynamics of irregular copolymers

Reptation dynamics of AB copolymers with irregular chemical structure are c onsidered theoretically. It is shown that interactions between A and B mono mers could result in a significant slowdown of copolymer dynamics in the di sordered (macroscopically homogeneous) state. The dynamical copolymer lengt h N* showing the crossover to the strongly retarded dynamics is calculated. It is shown that contour-length fluctuations (internal reptation modes) gi ve rise to a strong reduction of the slowdown effect and to a strong increa se of N* which becomes unrealistically high in the case of a genuinely rand om chemical structure. The following scaling dependence of N* is predicted for irregular block copolymers: N*proportional to delta(-8)chi(-8)n(0)(-8)N (c)(3), where delta is the degree of block polydispersity, chi the Flory AB interaction parameter, and Ilo the mean block length. The strongest dynami cal effect of AB interactions is predicted for correlated random copolymers near the critical point related to the formation of microdomain superstruc tures. [S1063-651X(99)03709-5].