Elastic Constants of Nematic Phenylpyrimidines Determined by Two Different Methods

Abstract

A survey of various methods to measure the elastic constants Kiof nematic liquid crystals is given. To determine K1, K3and the anisotropy of the diamagnetic susceptibility Δ x of two members of the 5n-hexyl-2-[4n-alkyloxy-phenyl]-pyrimidines and a mixture of both, we used a combined electromagneto-optical method, consisting in independent measurements of the optical phase difference in electric and magnetic fields acting on the same cell. The temperature dependence of the Krand K3-values for these phenylpyrimidines can be explained by common theories. The Δx data show the same temperature dependence as the values of the orientational order parameter S obtained by 1H-NMR. © 1990, Verlag der Zeitschrift für Naturforschung. All rights reserved.