Abstract

Molecular-Scale Modeling of Polymer-Nanoparticle Composites
The incorporation of nanoparticles (NPs) into polymers constitutes a powerful strategy for enhancing their thermomechanical properties and for introducing new optical, electrical, and magnetic functionalities into the polymers. This talk reviews our ongoing efforts in modeling the mesoscale morphology, assembly mechanisms, and thermomechanical properties of polymer nanocomposites. I will begin by discussing Monte Carlo simulations of polymer-grafted shaped NPs to elucidate the role played by polymer grafts in dictating the free-energy landscape, assembly pathway, and relative orientation of the NPs in their higher-order aggregates. These results have led to the development of a novel self-assembly strategy for fabricating tunable plasmonic nanojunctions within a polymer thin film. Next, I will describe an approach involving highthroughput quantitative image analysis and lattice models for inferring dynamic parameters of NP assembly from spatially and temporally disjointed images of composites. Application to shaped, metallic NPs reveals a cluster-cluster aggregation mechanism of assembly, where the NPs and their clusters diffuse in a Stokes-Einstein manner and stick with a probability that depends on their size and geometry as well as molecular weight of the surrounding polymer. Finally, I will discuss the application of atomistic and coarse-grained molecular dynamics simulations in predicting thermomechanical properties of polymer nanocomposites, especially viscoelastic behavior in the context of shock-mitigation materials, and mechanical flexibility and stability in the context of flexible organic semiconductors.