Liquid-gas equilibria in organic liquid crystals: M-24 (4-octyloxy-4′-cyanobiphenyl), BCH-52 (4-ethyl-4′-(trans-4-pentylcyclohexyl)biphenyl) and HP-53 (4′-propyl phenyl-4-(trans-4′-pentylcyclohexyl)benzoate)

•Vapor pressures of M-24, BCH-52 and HP-53 were measured at 345 - 500 K by TG-FSC•Thermodynamic functions of vaporization were derived•Vaporization parameters of liquid crystals were estimated by group contribution methods•Agreement between experimental and predicted values was discussed The vaporization characteristics of organic liquid crystals are unknown for the majority of these compounds. These properties may affect long timescale characteristics of devices based on liquid crystals, especially at the elevated temperatures. On the one hand, the estimation of these properties is complicated by the domain structure of a liquid crystal that cannot be accounted by existing group-contribution methods. On the other hand, the direct experimental measurement of vapor pressures and vaporization enthalpy is difficult because of the extremely low volatility caused by high molecular weight. Here we combined direct experimental measurements of the vapor pressure and a number of empirical structure-property relationships to obtain information about liquid-gas equilibria of three biphenyl-based organic liquid crystals, namely, M-24 (4-octyloxy-4′-cyanobiphenyl), BCH-52 (4-ethyl-4′-(trans-4-pentylcyclohexyl)biphenyl) and HP-53 (4′-propyl phenyl-4-(trans-4′-pentylcyclohexyl)benzoate) between 298.15 and 500 K. A comparison between the experimental values and calculations based on several group-contribution schemes was performed and the deviations were analyzed.