Diffusion of a Spherical Probe through Static Nematogens: Effect of Increasing Geometric Anisotropy and Long-Range Structure

Abstract

Diffusional behavior of a spherical probe through static nematogens (or needles) is probed via molecular dynamics simulations. The needles are modeled as spherocylinders and are arranged in idealized limits of an isotropic phase and a slowly quenched nematic mesh. The spherical probe exhibits superdiffusive motion through both the isotropic and nematic scatterer configurations. The superdiffusive behavior results from directional collisions between the spherical probe and the static nematogens. Velocity autocorrelation functions show long time correlations caused by directionality of transport due to the geometric anisotropy of the scatterers; however, glassy behavior exhibited by the tracer is observed when the scatterers are sufficiently long, leading to a downturn in the diffusion coefficients. Diffusion through the nematic configuration shows anisotropic diffusion with preferential motion occurring along the orientational director by way of effective channels formed by the long-range orientational order of the aligned nematogens.