Modifying Fragility and Collective Motion in Polymer Melts with Nanoparticles

TL;DR

This study uses molecular dynamics simulations to explore how nanoparticles influence the fragility and collective motion in polymer melts, revealing dependency on interaction strength and concentration, and interpreting results through Adam-Gibbs theory.

Contribution

It demonstrates how nanoparticles modify fragility and cooperative motion in polymer melts, linking these effects to thermodynamic theories and providing insights into material design.

Findings

Nanoparticles alter fragility and string length in polymer melts.

Effects depend on nanoparticle-polymer interaction and concentration.

Fragility correlates with temperature-dependent cooperativity.

Abstract

We investigate the impact of nanoparticles (NP) on the fragility and cooperative string-like motion in a model glass-forming polymer melt by molecular dynamics simulation. The NP cause significant changes to both the fragility and the average length of string-like motion, where the effect depends on the NP-polymer interaction and the NP concentration. We interpret these changes via the Adam-Gibbs (AG) theory, assuming the strings can be identified with the "cooperatively rearranging regions" of AG. Our findings indicate fragility is primarily a measure of the temperature dependence of the cooperativity of molecular motion.