Monte Carlo studies on the long time dynamic properties of dense cubic lattice multichain systems. II. Probe polymer in a matrix of different degrees of polymerization
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The dynamics of a probe chain consisting of n[subscript P]=100 segments in a matrix of chains of length of n[subscript M]=50 up to nM=800 at a total volume fraction of polymer φ =0.5 have been simulated by means of cubic lattice Monte Carlo dynamics. The diffusion coefficient of the probe chain over the range of n[subscript M]=under consideration decreases by about 30%, a behavior rather similar to that seen in real melts of very long chains. Furthermore, the analysis of the probe chain motion shows that the mechanism of motion is not reptation-like and that the cage effect of the matrix is negligible. That is, the local fluctuations of the topological constraints imposed by the long matrix chains (even for n[subscript M]=800) are sufficiently large to provide for essentially isotropic, but somewhat slowed down, motion of the probe, n[subscript P] =100, chains relative to the homopolymer melt. The results of these MC experiments are discussed in the context of theoretical predictions and experimental findings for related systems.