Static and dynamic scaling behavior of a polymer melt model with triple-well bending potential

TL;DR

This study uses molecular dynamics simulations to analyze the structural and dynamic properties of a polymer melt model, confirming ideal chain behavior at high temperatures and examining entanglement dynamics.

Contribution

It provides detailed characterization of a crystallizing polymer melt, validating ideal chain scaling and analyzing primitive paths and entanglement dynamics.

Findings

Polymer conformations follow Flory's ideality hypothesis for N > 50.

End-to-end distance and gyration radius scale as ideal chains.

Primitive path analysis supports Rouse and reptation theories.

Abstract

We perform molecular-dynamics simulations for polymer melts of the coarse-grained polyvinyl alcohol model that crystallizes upon slow cooling. To establish the properties of its high temperature liquid state as a reference point, we characterize in detail the structural features of equilibrated polymer melts with chain lengths $5\le N \le 1000$ at a temperature slightly above their crystallization temperature. We find that the conformations of sufficiently long polymers with $N >50$ obey essentially the Flory's ideality hypothesis. The chain length dependence of the end-to-end distance and the gyration radius follow the scaling predictions of ideal chains and the probability distributions of the end-to-end distance, and form factors are in good agreement with those of ideal chains. The intrachain correlations reveal evidences for incomplete screening of self-interactions. However, the observed deviations are small. Our results rule out any pre-ordering or mesophase structure formation that are proposed as precursors of polymer crystallization in the melt. Moreover, we characterize in detail primitive paths of long entangled polymer melts and we examine scaling predictions of Rouse and the reptation theory for the mean squared displacement of monomers and polymers center of mass.