Characterization of a Nematic Mixture by Reversed-Phase HPLC and UV Spectroscopy: Application to Phase Behavior Studies in Liquid Crystal-CO2 Systems

In the present work a simple but selective reversed-phase high performance liquid chromatographic method (HPLC) was developed for analysis of the nematic liquid crystal mixture E7 to precisely determine the composition of the liquid crystal mixture used in PDLC films preparation. Ultra-violet absorption spectrophotometry (UV) experiments were carried out to determine the HPLC detection wavelength and to characterize the absorptivity constants of E7 constituents. The developed technique is applied in the case of equilibrium solubility studies for E7 in supercritical carbon dioxide (scCO2). The results indicate unambiguously that scCO2 can fractionate the mixture towards the E7 components. The four single components peaks of the E7 mixture were distinctively separated by this method which enabled the determination of the solubility of E7 constituents in the scCO2.