Translational Diffusion of CH₄ and CH₂Cl₂ Dissolved in Cholesteric Liquid Crystals

Abstract

Translational diffusion coefficients of CH, and CH2CI2 dissolved in five cholesteric mixtures of alkylcyanobicyclohexane-cholesterylchloride were measured in the temperature range 25°Cto 75"C, using the NMR pulse gradient spin echo method. The pitch of the solvents studied depends on the cholesterylchloride concentration and ranged between m and 2 . 2~. The results indicate a slight difference in the diffusion constant parallel (011) and perpendicular (I) to the cholesteric pitch axis, with DJDll = 1.1. The Arrhenius activation energies for the diffusion constants are about 6 to 7 kcal/mole for both probes. No dependence of the diffusion coefficients on the cholesterylchloride concentration and thus on the pitch was observed.