The influence of concentration on the dynamics of cubic lattice chains

A simple cubic lattice model was developed to study the dynamics of linear polymer chains as a function of concentration and chain length. The chain movement algorithm included both the normal bead motion and a 90° crankshaft motion. Three dynamic properties were studied: the terminal relaxation time as estimated from the long time behavior of the end-to-end vector autocorrelation function, the center-of-mass diffusion constant, and the diffusion of the central chain monomer. The model was tested with single chains and was found to agree with the Rouse model and with results reported by others. With increasing concentration the behavior of the relaxation times and diffusion constants as a function of chain length became less Rouse-like and appeared to be approaching behavior predicted by the theory of reptation. Diffusion of the center monomer also deviated from the predictions of the Rouse model at high concentrations However, it is unclear if it is approaching behavior predicted by the reptation model.