STATICS AND DYNAMICS OF DENSE COPOLYMER MELTS - A MONTE-CARLO SIMULATION STUDY

Using the bond-fluctuation-algorithm we perform dynamic Monte Carlo si mulations on dense symmetric copolymer melts. We cover structures from homogeneous melts to strongly separated regimes. We confirm the scali ng laws found in previous simulations for the static properties of the chains and extend these laws into the strong segregation region;The s tructure factor and various other static properties of the single chai n scale with EN. We observe that in the homogeneous phase even for sho rt chains the A- and B-blocks contract due to the prevailing comonomer repulsion. The center-of-mass diffusion of single chains as well as t he relaxation of the end-to-end vector exhibit a crossover between two regimes above and below the order-disorder transition. We find that i n both regimes the dynamics do not scale with EN. In the strong segreg ation limit the diffusion coefficient turns out to be lower than the e xpected value of 2D(0)/3. The end-to-end-vector displays two relaxatio n processes even well above the order-disorder transition. Besides a f ast mode we find a slow mode, more than a decade apart. The simulation s show that composition fluctuations above the order-disorder transiti on have a profound influence on the dynamics. (C) 1997 American Instit ute of Physics.