Electrochemical Measurements of Anisotropic Diffusion in Thin Lyotropic Liquid Crystal Films Using Interdigitated Array Electrodes

Abstract

A new application of interdigitated array (IDA) electrodes is described for diffusion measurements of electrochemical probes dissolved in thin, lyotropic liquid crystalline films. The liquid crystal is a solution of 32% (w/w) lithium 4-trans-n-pentyl cyclohexanoate (Li5CH) in water, which can be prepared as well-ordered films of thickness less than ca. 12 {mu}m. Apparent diffusion coefficients (D{sub APP}) of the electrochemical probes are calculated from steady-state currents of generator/collector voltammograms. The diffusional anisotropy, measured parallel and perpendicular to the liquid crystal director, increases with increasing hydrophobicity of the probes. A simplified model has been developed to explain the diffusional anisotropy of hydrophobic probes in the ordered film. The transition temperature of the liquid crystal is determined from an activation plot of D{sub APP} for 1,1{prime}-dimethylferrocene. 32 refs., 6 figs., 1 tab.