Thermodynamic and separation properties of 4-(octyloxy) benzoic acid liquid crystals by inverse gas chromatography (IGC)

The thermodynamic properties of 4-(octyloxy) benzoic acid (OBA) liquid crystal (LC) were investigated at infinite dilution by inverse gas chromatography (IGC). The phase transition temperatures of OBA LC were determined by differential scanning calorimetry (DSC) and IGC. The thermodynamic region was determined to be between 160 and 170 degrees C. Specific retention volumes were calculated using IGC measurements to prepare retention diagrams. The results from the diagrams were used to characterize the thermodynamic properties of the OBA LCs. Based upon these properties, the solvents used in this study were determined to be unsuitable for OBA LCs. The separation of structural isomer series (butyl acetate, butyl alcohol, and amyl alcohol series) was studied by an OBA LC coated Chromosorb W stationary phase in the thermodynamic region. This system was able to distinguish the isomers according to the determined selectivity coefficients.