SIMULATION STUDIES OF EXCLUDED VOLUME EFFECTS ON POLYMER-CHAIN DYNAMICS IN SEVERAL NONLATTICE MODELS

Computer simulations of off-lattice bead-stick models of polymer chains with a variety of move rules have been carried out to gauge the effect of these move rules on the dynamical behavior of the chains. We report long relaxation times, translational diffusion constants, and mean-square end-to-end length for chains of from 9 to 99 beads, both with and without excluded volume. For several move rules the excluded volume constraints increase the chain-length dependence of the long relaxation times by about the square root of chain length, roughly twice the exponent expected from simple scaling arguments based on the expansion of equilibrium dimensions by excluded volume. Move rules analogous to some of those used in the present study have been employed by others in previous lattice-model studies. Those earlier lattice-model results appeared to suggest that relaxation times scale like mean-square chain dimensions. Our present results suggest, however, that the earlier result is an artifact resulting from the combination of lattice constraints with the use of move rules explicitly dependent upon local chain conformation.