|Title||MOLECULAR-DYNAMICS COMPUTER-SIMULATION OF POLYISOPRENE LOCAL DYNAMICS IN DILUTE TOLUENE SOLUTION|
|Publication Type||Journal Article|
|Year of Publication||1995|
|Authors||Moe, N. E., and M. D. Ediger|
|Type of Article||Article|
|Keywords||BROWNIAN DYNAMICS, CHAIN DYNAMICS, CIS-1,4-POLYBUTADIENE, CONFORMATIONAL, GLASS-TRANSITION, NMR, POLYMERS, POLYSTYRENE, SPIN RELAXATION, TIME-CORRELATION FUNCTIONS, TRANSITIONS|
Fully atomistic molecular dynamics computer simulations have been performed on a polyisoprene chain of 35 repeat units in a solution of 207 toluene molecules. Simulated orientation correlation functions of polymer C-H vectors compare favorably with C-13 NMR experiments. In particular, the ordering of the different correlation times is as expected, and their absolute values agree with experiment within a factor of 2. Also in good agreement with experiment, backbone C-H correlation functions were found to be nearly exponential after a very fast small-amplitude decay. The simulation trajectories have been analyzed to examine the changes in atomic positions and torsional coordinates which accompany conformational transitions. Adjustments in these degrees of freedom are found to be localized to 1-2 repeat units in polyisoprene, in good agreement with the results of previous Brownian dynamics simulations. Cooperative pairs of conformational transitions account for less than half of all transitions if coupling up to second neighbors is considered. About two-thirds of all transitions occur in cooperative pairs if coupling up to ninth neighbors is considered.