Calorimetric Study on Optically Isotropic Liquid Crystals

Heat capacities of optically isotropic mesogens, BABH(8), ANBC(16) and ANBC(18), have been measured by adiabatic calorimetry. The existence of solid-solid phase transitions with large entropy change seems to play a characteristic role for formation of the isotropic mesophase. Entropies of transition between the isotropic mesophases and the neighboring liquid crystalline phases are quite small. On the basis of the entropies of transition the possibility is suggested that the molecules might be aggregated in an identical manner in these two phases.