A Series of Di-Schiff Base Liquid Crystals. Studies with Gas-Liquid Chromatographys and Differential Scanning Calorimetry

Abstract

A di-Schiff base liquid crystal series with terminal alkyl substituents was synthesized. Phase transition temperatures and nematic-isotropic thermodynamic properties are reported for the methyl through n-hexyl, and n-octyl members. All are mesomorphic except the unsubstituted hydrogen homologue. The nematic-isotropic transition temperatures and entropies show the usual alternations characteristic of a high-melting series. Relative retention data for the isomeric rigid solute probes phenanthrene and anthracene, in the nematic region of five liquid crystal stationary phases was correlated with the degree of order in the mesophase. The mechanism of gas-liquid chromatographic shape-dependent selectivity of nematic stationary phases towards isomeric polycyclic aromatic hydrocarbons is examined in light of current solution thermodynamic theory.