(585b) Entanglements and Chain Conformations in Model Polymer-Grafted Nanoparticle Monolayers

Neat polymer-grafted nanoparticles (PGNs), consisting solely of nanoparticles (NPs) protected by grafted polymer chains, possess improved spatial dispersion of NPs relative to typical bare NP-filled polymer composites. In thin films, PGNs can self-assemble into a well-defined hexagonally packed structure, resulting in unique mechanical, optical, and electronic properties. We use simulations to connect the PGN architecture, in particular graft density and chain length, to the polymer conformations, degree of interpenetration of chains on neighboring particles, and amount of entanglements. Specifically, we used coarse-grained molecular dynamics (MD) simulations to study PGNs deposited on a smooth attractive surface in a hexagonally packed monolayer. With increasing graft density, we observe decreasing interpenetration of chains on nearby particles and a corresponding increase in localization of entanglements to the interstitial regions between the particles where the chains have the most conformational freedom. Additionally, in high graft density systems, we observe local alignment of chains orthogonal to the NP surface, which decreases as a function of distance from the NP surface. By showing how experimentally controllable parameters such as graft density impact the molecular-level structure in PGN thin films, we aim to guide the design of future materials.