title: Modifying fragility and collective motion in polymer melts with nanoparticles.
abstract: We investigate the impact of nanoparticles (NP) on the fragility and cooperative stringlike 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 stringlike motion, where the effect depends on the NP-polymer interaction and NP concentration. We interpret these changes via the Adam-Gibbs (AG) theory, assuming the strings can be directly identified with the abstract "cooperatively rearranging regions" of AG. Our findings indicate that fragility is primarily a measure of the temperature dependence of the cooperativity of molecular motion.
authors.affiliation: Department of Physics, Wesleyan University, Middletown, Connecticut 06459, USA.
authors.forename: Francis W
authors.initials: FW
authors.lastname: Starr
authors.forename: Jack F
authors.initials: JF
authors.lastname: Douglas