Reptation, NSE and Computer Simulation

Compared to the available clear-cut comparisons between NSE results and simulations for short Rouse chains, the situation in the entangled regime is less satisfactory. The molecular dynamics (MD) simulation of ensembles of suffi- 

While the simulation times for N=350 were long enough to reach the diffusive regime, the data for N=700 and 10,000 just reach far into the predicted reptation regime. After an initial Rouse-like motion for inner chain 

On the other hand, the group of Briels [54] recently proposed a coarse graining in terms of blobs with coarse grained properties determined beforehand by atomistic simulations. The mean-square displacement of these blobs displays only a very narrow Rouse regime and then is slowed down further, but never reaches the power law of reptation. The authors relate this observation to the shortness of the chains ( 8 entanglement lengths) and their averaging over all blobs (not only the innermost ). 

We conclude this brief discussion of recent results on the segment mean-square displacement (msd) with a brief look at the latest atomistic simulation put forward by Harmandaris et al. [53]. In this simulation fully atomistic PE 

The dashed line refers to the Cyg PE melt and is clearly seen to obey the scaling laws predicted by the Rouse model a short time behaviour where and 

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