Abstract
Discontinuous molecular dynamics simulations are performed on systems containing 32 hard chains of length 192 at three volume fractions, φ=0.40, 0.45, and 0.50, to investigate the effect of position on the segmental mean squared displacement. The mean squared displacements of various sized blocks of segments at different positions along the chain are calculated. First, the effect of block size on the dynamics of end and middle blocks is considered. It is found that small blocks provide a greater difference between the mean squared displacements of middle blocks, end blocks, and the whole chain than larger equal-sized blocks. Next, the portions of the chain exhibiting end and middle behavior are determined. It is found that a large portion of the chain displays middle behavior, while a small portion displays end behavior. Finally, the dynamics of segment relaxation along the chain are studied. The relaxation of small blocks of segments at different positions along the chain starts at the chain ends and progresses toward the chain middle with time, as the tube model predicts. The minor chain length, the portion of the chain that has relaxed, follows a power law with time, but the power is somewhat less than predicted.
Published Version
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