The effect of chain interpenetration on an ordering process in the early stage of polymer crystal nucleation

In the present study, the degree of chain interpenetration was considered as a structural attribute of the entanglements in polymer chain system. Inter-chain radial distribution function (RDF) was used to perform this measurement. We applied this method to a model system, in which an ordering process in the early stage of polymer crystal nucleation at the atomistic level was simulated by means of molecular dynamics (MD). Initial chain structures possessed different degrees of interpenetration and underwent the ordering process at 400 K. Obtained results indicated that at the nanosecond scale the degree of interpenetration impedes the ordering process remarkably, which agrees with the experimental observation at laboratory time scale. Such behavior among chains indicates that at the atomistic level a creeping polymer chain is able to recognize if the neighbor group on the ‘tube’ is from the same chain or other chains. This recognition manifests that the reptation time of a chain would be influenced by the ‘tube’ composition or the degree of interpenetration. It also showed that the degree of interpenetration changes little during the ordering process, which means that the motion of the chain segments is mainly predominated by the ordering process rather than further adjusting the entanglement extent under the conditions simulated.