Optical and Dilatometric Properties of Binary Mixtures of PAA and PHAB

The nematic isotropic phase boundary, dilatometric properties and refractive indices of p-azoxyanisole (PAA), p, p'-di-n-hexyloxyazoxybenzene (PHAB) and their mixtures are reported. The refractive index and density data are used to calculate the mean polarizabilities of the PAA/PHAB mixtures and to calculate the temperature dependence of the order parameters of the PAA/PHAB mixtures using both the Vuks and the Neugebauer descriptions of the local field. It is seen that the PAA/PHAB mixture order parameters at the reduced temperature t = 0.013 appear to follow the additive rule.