COMPUTER-SIMULATION OF VISCOELASTICITY IN POLYMER MELTS

A method is presented for the simulation by molecular dynamics of stress relaxation in polymer melts. It is applied to dense model systems of short freely-jointed chains with repulsive excluded-volume interactions. Stress histories are fitted by a Prony series. The model parameters when subjected to Caswell-Paboojian scaling agree well with values observed for real systems. In contrast to the usual assumption, the shear stress is found to be due to the excluded-volume interactions and not to the forces in the covalent bonds of the chain. The utility of the entropic spring concept in the earlier stages of stress relaxation is also placed into question by these simulations.