Chain Flexibility and the Segmental Dynamics of Polymers

TL;DR

This study uses molecular dynamics simulations to explore how chain length and torsional barriers influence polymer segmental dynamics, revealing effects like pressure densification and deviations in relaxation times linked to torsional rigidity.

Contribution

It uncovers the role of torsional rigidity in polymer dynamics, explaining experimental features absent in simpler models.

Findings

Reduced volume effect on dynamics with longer chains

Pressure densification capacity increases with chain rigidity

Deviation from constant Johari-Goldstein relaxation at fixed segmental relaxation time

Abstract

Using molecular dynamics simulations we examine the dynamics of a family of model polymers with varying chain length and torsional potential barriers. We focus on features of the dynamics of polymers that are seen experimentally but absent in simulations of freely rotating and freely jointed chains. The reduced effect of volume on the segmental dynamics with increasing chain length, a capacity for pressure densification, and the deviation from constant Johari-Goldstein relaxation time at constant segmental relaxation time all have a common origin - torsional rigidity, and these effects become increasingly apparent for more rigid chains.