MOLECULAR-DYNAMICS COMPUTER-SIMULATION OF LOCAL DYNAMICS IN POLYISOPRENE MELTS

Fully atomistic molecular dynamics computer simulations of cis-polyiso prene melts have been performed. Two different methods were used to ge nerate four initial configurations. The local polymer dynamics were su bstantially independent of initial chain configuration. The ratios of correlation times for different C-H vectors in the chain backbone matc h experiment very well. Absolute correlation times from the simulation are about 2.5 times slower than experimental values. The correlation functions obtained from the simulations are strongly non-exponential, in general agreement with experiment. The local dynamics in these simu lations are fairly isotropic, in marked contrast to results reported f rom simulations of polyethylene melts by Takeuchi and Roe. Several ana lysis techniques indicate that the spatial extent of the cooperative m otion that accompanies conformational transitions in polyisoprene melt s is about 1-2 repeat units. A similar length scale was found recently in simulations of polyisoprene in a dilute solution. Copyright (C) 19 96 Elsevier Science Ltd.