Using Theory and Simulations To Calculate Effective Interactions in Polymer Nanocomposites with Polymer-Grafted Nanoparticles

Abstract

Using theory and large-scale simulations, we demonstrate how one can program structure and thermodynamics into polymer-grafted particles filled polymer nanocomposites (PNCs). We simulate varying graft (G) and matrix (M) polymer compositions for varying model graft–matrix bead pairwise interactions, χGM, and calculate structural features and the effective graft–matrix interaction parameter, χGMeff, in the PNC. Varying the graft (G) and matrix (M) polymer compositions provides tunability of morphology (particle dispersion/aggregation) and graft–matrix interpenetration at each χGM. Thermodynamically, for all composites the χGMeff exhibits negative values (effective attraction) at low values of χGM, with a sharp transition to positive values (effective repulsion) at large values of χGM. The sharp transition in χGMeff coincides with the structurally characterized particle dispersion–aggregation transition marked by the onset of upturn in the matrix–matrix structure factor at zero wavenumber. Strikingly, regard...