Order and Flow of Liquid Crystals: The Nematic Mesophase

Abstract

Liquid crystals offer a unique opportunity for physical studies. The nematic mesophase is an aggregate, yet fluid state, which consists of anisometric, rodlike structures. The flow of three nematic-forming compounds, p-azoxyanisole, anisaldazine, and p-anisal-p-aminoazobenzene, was studied in both their isotropic and anisotropic states. Studies were made with capillary viscometers and with a high-shear concentric cylinder viscometer. New density, coefficient of expansion, and transition temperature data are also given. The instrumentation used is described. The results add definition to the viscosity and density anomalies at nematic-isotropic transitions. The data for p-anisal-p-aminoazobenzene are entirely new. Values for anisaldazine establish previous viscosity and density results on an absolute basis. New results on p-azoxyanisole contribute a temperature and shear rate extension to previous studies.