Unveiling the impact of nanoparticle size dispersity on the behavior of polymer nanocomposites

Abstract

Polymer nanocomposites (PNCs), a class of polymer materials incorporating nano-sized particles (NPs), have tremendous potential in industrial formulations and technological applications, such as protective coatings and food packaging. In this work, we perform Molecular Dynamics simulations to unveil the impact of NP size dispersity on a variety of properties that characterize the response of PNCs at the nano and macro scales. In particular, at the nano scale, we investigate the space distribution of small and large polydisperse NPs and their ability to diffuse through a dense isotropic distribution of unentangled polymer chains. We find very interesting scaling laws relating the average size and polydispersity index of NPs with their diffusion coefficients, generally underestimated by existing theoretical models. These theories are here adapted to include the effect of NP size dispersity and their predictions, confirming the relevance of incorporating such contributions, are validated against our simulation results. We also analyze the diffusivity of the polymer chains as a function of the interparticle distance for a spectrum of NP diameters and confirmed the existence of a single master curve as recently observed experimentally (S. Gam et al., Soft Matter, 2012, 8, 6512). To assess the effect of NP size dispersity on the macroscopic response of our model PNC, we evaluate two key transport properties, shear viscosity and thermal conductivity, which are found to display an intriguing universal behavior when plotted against the polymer/NP specific interface area and the inverse of the NP's mass, respectively.