Simulation of diffusion and relaxations of non-dilute star chains

Star polymer chains with 12 arms in a good solvent have been investigated using a dynamic Monte Carlo algorithm with the bond fluctuation model in the dilute, semidilute and concentrated regimes. We have characterized the self-diffusion coefficient and different relaxation modes of individual chains. We discuss the variation of the results with the arm length (or number of beads) and concentration. The ratio of diffusion coefficient of a star to that of a homologous linear chain is shown to increase progressively with concentration for overlapped non-entangled chains. It is also observed that diffusion and elastic relaxation of individual arms are more sensitive to the chains overlapping than global rotation or disentanglement between arms.