Diffusion of Impurities in Smectic A Phases

Abstract

A simple model, based on a hybrid of solid state and liquid theory, is introduced to obtain the impurity diffusion tensor of spherical molecules at low concentration in ordered systems. The anisotropy ratio of the diffusion coefficients D⊥ (perpendicular to the preferred direction of molecular alignment) and D (parallel to it), for tetramethylsilane (TMS) dissolved in the smectic A liquid crystal of 4-n-butoxybenzylidene-4′-n-octylaniline (BBOA) is calculated at the temperature T = 53[ddot]C. The result D⊥/D∥ = 8.6 agrees rather well with the experimental data of Murphy et al.