Some Flow Characteristics of Mesophase Types

Characteristic flow properties for each of the three nominal mesophase types have been empirically established. Results are given for the nematic, smectic, and cholesteric types of mesophase. Discussion is centered on mesophases or liquid crystals exhibited by pure compounds within defined temperature intervals between the regular solid and the isotropic liquid. For nematic mesophases, the prominent flow orientation, consequent low viscosity, and the unusual flow behavior near the nematic—isotropic transition are discussed. The remarkably high and shear-dependent viscosities of cholesteric mesophases are contrasted to the simple flow properties of these cholesterol derivatives at temperatures for their respective isotropic liquids. Descriptions of flow properties for smectic mesophases are based essentially upon data on a single compound, ethyl-p-azoxybenzoate. Viscosity data on this compound from several sources are intercompared for the first time. Some of the new empirical conclusions given here are at variance with those reported previously in several reviews.