Adiabatic scanning calorimetry study of ionic liquid crystals with highly ordered crystal smectic phases

Adiabatic scanning calorimetry was used to study four ionic liquid crystals whose phase sequences include highly ordered crystal smectic phases (crystal smectic E or T phases). The ionic liquids were based on piperidinium or morpholinium cations with long alkyl chains; the anions were tetrafluoroborate or hexafluorophosphate. High-resolution heat capacity and enthalpy data were obtained, from which the total transition heat and latent heat for the observed phase transitions were determined. All transitions displayed a non-zero latent heat and were thus found to be first order.