ROUSE AND REPTATION DYNAMICS AT FINITE TEMPERATURES - A MONTE-CARLO SIMULATION

The temperature dependence of the dynamics of polymer chains in the melt is studied in a Monte Carlo simulation of the bond fluctuation model. Temperature enters via a bond angle potential determining the stiffness of the chains. The model is simulated at a melt volume fraction of PHI = 0.5 and for chains of lengths N = 20, 50, 100, and 200. For the short chains we are determining the temperature range over which a random coil description of these semiflexible chains is possible, i.e. the temperature region for which the chains show the behavior of random coils in the melt. We then examine to what extent the Rouse model is able to describe the dynamics of these chains. We will look especially at the Rouse scaling for the dynamic structure factor. For the longest chains it has been shown that our model in the athermal limit can be described by the reptation picture of DeGennes and Doi and Edwards and the density dependence of the tube diameter has been established. Here we now measure the temperature dependence of this dynamic length scale by analyzing the dynamic structure factor. It is shown to decrease slightly with decreasing temperature in accord with recent findings of neutron spin echo experiments.