Influence of Nanoparticle Additives on the Fragility of Polymer Glass Formation and the Buchenau Relation

TL;DR

This study uses molecular dynamics simulations to explore how adding nanoparticles affects the fragility of polymer glasses and confirms the Buchenau relation linking local stiffness fluctuations to relaxation dynamics.

Contribution

It demonstrates the influence of nanoparticle volume fraction on polymer glass fragility and validates the Buchenau relation across different nanoparticle interactions.

Findings

Fragility significantly changes for nanoparticle volume fractions above 5%.

Fragility correlates with the inverse variance of the Debye-Waller factor.

The Buchenau relation holds for all nanoparticle concentrations and interaction types.

Abstract

We investigate the impact of the addition of nanoparticles (NP) on the fragility of a model glass-forming polymer melt by molecular dynamics simulations. We find significant changes in fragility for nanoparticle volume fractions $\phi$ exceeding $\approx$ 5%, where fragility changes correlate with the inverse variance of the magnitude of the Debye-Waller factor $<u^2>$, a measure of local "stiffness" fluctuations. We also confirm the validity of the Buchenau relationship between $<u^2>$ and the structural relaxation time $\tau$ for all $\phi$ and polymer-NP interaction types.