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.
@article{arxiv.1101.5567,
title = {Modifying Fragility and Collective Motion in Polymer Melts with Nanoparticles},
author = {Francis W. Starr and Jack F. Douglas},
journal= {arXiv preprint arXiv:1101.5567},
year = {2015}
}