Chain Conformations in Model Polymer-Grafted Nanoparticle Monolayers

Neat polymer-grafted nanoparticles (PGNs) are promising materials consisting of only nanoparticles (NPs) with polymer chains grafted to their surface. The presence of only grafted polymer mitigates demixing issues observed in NP-filled polymer composites. These materials can have a well-defined nanoscale structure and desirable mechanical, optical, and electronic properties. Mechanical properties can depend sensitively on graft density through changes to polymer brush conformation, interpenetration, and degree of entanglement.

Coarse-grained MD simulations are used to study the behavior of a hexagonally packed monolayer of PGNs deposited on a smooth surface. The influence of graft density on the film’s nanoscale structure and on the alignment of grafted chains is probed to understand their connection with degree of entanglement and to mechanical properties. The amount of interpenetration of grafted chains on neighboring PGNs increases with decreasing graft density, and this is related to the amount of entanglements per chain. We also find local alignment of chains orthogonal to the NP surface, which subsides with distance from the NP’s surface.