Relaxation of flexible chains in dilute and non-dilute systems. Dynamic Monte Carlo results for linear and star chains

A dynamic Monte Carlo algorithm is employed to investigate the dynamics of flexible linear and star chains on a cubic lattice at different concentrati ons. Some results for similar systems are also obtained with an off-lattice algorithm. Diffusion coefficient, relaxation times and mean size data are combined into friction-independent ratios in good agreement with the theore tical predictions from the Rouse theory. The relaxation times and amplitude s corresponding to the Rouse normal modes are analyzed in terms of their va riation with the mode order. The end-to-end vector correlation times obtain ed from the simulations for linear chains are compared with the theoretical expression obtained from the Rouse theory. Deviations from this theory an observed for the contribution of the different modes in the non-dilute syst ems. Finally, the time correlation function corresponding to a subchain's e nd-to-end vector is investigated. The results also show deviations from the Rouse theory, which are in qualitative agreement with the features observe d in data from dielectric relaxation experiments of block copolymers.