Crossover temperature (T CO) and the temperature gradient of refractive indices of a homologous mixture of 4O.6 and 6O.4

Abstract

Temperature gradient of refractive indices, dn e /dT and dn o /dT, of the isotropic mixtures of the liquid crystals of nO.m compounds, namely N-(p-n-butyloxybenzylidene)-p-n-hexyl aniline, 4O.6, and N-(p-n-hexyloxybenzylidene)-p-n-butyl aniline, 6O.4, are estimated using the refractive index data. The former one exhibits a second-order nematic-to-smectic-A (N-SmA) phase transition, while the later compound shows a first-order (N-SmA) phase transition. These two compounds exhibit high clearing temperatures, i.e. well above the room temperature. It is found that the two materials and the mixtures exhibiting second-order N-SmA transition show the crossover temperatures (T CO’s) well below the room temperature while the mixtures showing first-order transition exhibiting T CO’s well above the room temperature.