Anomalous Diffusion of Smooth Nanorods in Polymer Nanocomposites

Polymer nanocomposites (PNCs) are diverse, soft materials which comprise a polymer matrix with nanoparticle fillers. PNCs’ tailorable properties have garnered recent interest in applications including plastics, electronics, coatings, and sensors. The structure and dynamics of PNCs determine their viability for specific applications, such as dispersion for enhanced mechanical properties, percolated structures for electrical conductivity, and diffusion of tracers in nanorheology. In this talk, coarse-grained molecular dynamics simulations on the diffusion of thin nanorods in polymer melts as a function of nanorod roughness and aspect ratio will be presented. We observe anomalous nanorod diffusion with decreasing nanorod roughness, which results in nonlinear scaling behavior of diffusion coefficients with nanorod length. The anomalous diffusion for smooth rods is related to non-Gaussian diffusion and the existence of dynamic heterogeneities, quantified in terms of Van Hove correlation functions. The combined effects of nanorod roughness and nanorod diameter is investigated, in which case anomalous diffusion for smooth versus rough nanorods is also observed. This work highlights the ability to tune nanorod roughness and aspect ratio to achieve unique rod dynamics and provides mechanistic insights into the diffusion of anisotropic particles in synthetic and biological media.