Electrolyte effects on the nematic-isotropic phase transition in lyotropic liquid crystals

A phenomenological approach to the description of the electrolyte effect on the nematic–
isotropic phase transition in lyotropic liquid crystals is proposed. The influence of the
electrolyte is discussed by varying the coupling between the concentration variables and the
orientational order parameter. The analysis shows that the discontinuity in the first order
nematic–isotropic phase transition as measured by TNI{T0 increases as a function of the NI
weight fraction of the electrolyte. Here TNI is the first order nematic–isotropic phase transition temperature and TN0I is the extrapolated supercooling limit. The electrolyte dependence of the Cotton–Mouton coefficient and the non-linear dielectric effect in the isotropic phase above the nematic–isotropic phase transition are calculated. The theoretical predictions are found to be in good agreement with experimental results.