Physical studies of nematic azoxybenzenes. I. Magnetic susceptibilities and the order parameter

Abstract

The anisotropy of the magnetic susceptibility and the density of the series of nematic p,p′-di-n-alkyl and p,p′-di-n-alkoxy azoxybenzenes are reported as a function of temperature. Assuming that the molecules are effectively axially symmetric the anisotropy of the susceptibility is a direct measure of the nematic order parameter S. The results for S agree reasonably well with the predictions from Maier and Saupe’s theory of the nematic phase. With increasing chain length both the order parameter and the relative volume change at the nematic–isotropic transition alternate parallel to the nematic–isotropic transition temperature and the transition entropy.