Molecular Dynamics Simulation Study of Nonconcatenated Ring Polymers in a Melt: I. Statics

TL;DR

This study uses molecular dynamics simulations to analyze the static structural properties of nonconcatenated ring polymer melts, revealing a crumpled globule conformation and extensive surface interactions, contrasting with linear polymers.

Contribution

It provides detailed insights into the static conformations and packing of ring polymers, highlighting differences from linear polymers and supporting the crumpled globule model.

Findings

Ring polymers exhibit a crumpled globule conformation.

Most beads in rings are surface beads interacting with others.

Structural properties differ significantly from linear polymers.

Abstract

Molecular dynamics simulations were conducted to investigate the structural properties of melts of nonconcatenated ring polymers and compared to melts of linear polymers. The longest rings were composed of N=1600 monomers per chain which corresponds to roughly 57 entanglement lengths for comparable linear polymers. For the rings, the radius of gyration squared was found to scale as N to the 4/5 power for an intermediate regime and N to the 2/3 power for the larger rings indicating an overall conformation of a crumpled globule. However, almost all beads of the rings are "surface beads" interacting with beads of other rings, a result also in agreement with a primitive path analysis performed in the following paper (DOI: 10.1063/1.3587138). Details of the internal conformational properties of the ring and linear polymers as well as their packing are analyzed and compared to current theoretical models.