Estimation of mechanical properties of interfaces in polymer nanocomposites using molecular dynamics

Polymer nanocomposites are candidates for the next-generation of cable insulation and capacitor dielectrics. Nanoscale fillers, due to their high surface area, drastically increase the interfacial region which improves the dielectric permittivity and breakdown strength of the nanocomposites. Understanding the role of these interfaces in mechanical response of nanocomposites is crucial for their robust design. Modelling them at the molecular scale can capture the nanoscale features of the filler surface, the amorphous nature of the polymer and the interaction between them, while keeping the computational cost low. Using molecular dynamics, we calculate mechanical response of an ensemble of composites where polymer chains are grafted on a filler surface. We study the role of graft density and filler surface curvature on the stress and displacement field near the interface. We use an iterative finite-element-based approach to extract elastic modulus variation near the interface from the molecular dynamics stress and displacement profiles, which provides a starting point for large-scale modeling of composite nanostructures from first principles.