Investigation of mesophase transitions in liquid crystals using inverse gas chromatography

Abstract

Inverse Gas Chromatography, IGC, has been used to study phase transitions in three low molar mass liquid crystals and one side-chain liquid crystalline polymer. This extension of previous work has shown that transitions between all of the various mesophases can be detected and their temperatures measured with an accuracy and precision comparable to that of more conventional techniques. For one of the compounds, 4,4′-(n-hexyloxy)cyanobiphenyl, the kinetics of solidification from the supercooled nematic phase have been measured. The process took place in two stages which could be interpreted in terms of a modified version of the Avrami model of polymer crystallization. An explanation of the results is that the solid support is providing a large number of nucleation sites for the initial part of the solidification, which is completed in a slow, diffusion-limited process. However, further work is required to confirm this mechanism. Keywords: inverse gas chromatography (IGC), liquid crystals, mesophase transitions, activity coefficients, retention volumes.