Dynamic Arrest in Polymer Melts: Competition between Packing and Intramolecular Barriers

TL;DR

This study uses molecular dynamics simulations to explore how intramolecular barriers influence the glass transition in polymer melts, revealing a competition with packing effects that affects relaxation dynamics.

Contribution

It introduces a systematic analysis of intramolecular barriers' impact on polymer glass transition, highlighting differences from simple glass-formers.

Findings

Large MCT exponent parameter values observed.

Competition between packing and intramolecular barriers affects dynamics.

Differences identified between polymers and simple glass-formers.

Abstract

We present molecular dynamics simulations of a simple model for polymer melts with intramolecular barriers. We investigate structural relaxation as a function of the barrier strength. Dynamic correlators can be consistently analyzed within the framework of the Mode Coupling Theory (MCT) of the glass transition. Control parameters are tuned in order to induce a competition between general packing effects and polymer-specific intramolecular barriers as mechanisms for dynamic arrest. This competition yields unusually large values of the so-called MCT exponent parameter and rationalize qualitatively different observations for simple bead-spring and realistic polymers. The systematic study of the effect of intramolecular barriers presented here also establishes a fundamental difference between the nature of the glass transition in polymers and in simple glass-formers.