Thermodynamic investigation of the metastable phases of TBBA

An investigation was performed by differential scanning calorimetry on the metastable phases (VI and VII) of TBBA liquid crystal.In addition to the reversibility of the transitions smectic B- phase VI and phase VI-phase VII, a supercooling effect at this last transition and a large spread in the crystallization temperature were observed.Furthermore the transition entropies were determined together with a more correct phase diagram of TBBA.All these data refer to the first complete loop which was obtained by heating the virgin sample from room temperature to the smectic B phase and then cooling it again to room temperature.A different behaviour was obtained in the following complete loops. This behaviour, which cannot be explained at present, constitutes the basis for further experiments by other techniques.