A study of the nematic-smectic A-smectic C point in a binary liquid-crystalline mixture by adiabatic scanning calorimetry

Abstract

An adiabatic scanning calorimetric technique has been used to investigate the nematic-smectic A-smectic C (NAC) multicritical point in mixtures of 4-n-pentyl-oxyphenyl-4′-n-octyloxybenzoate and 4-n-hexyloxyphenyl-4′-n-octyloxybenzoate. The NC transitions are weakly first order and the latent heat becomes zero at or very near the NAC point. Near the NAC point no thermal feature associated with the NA transitions could be observed. The heat capacity anomalies along the second order AC transition line and along the first order NC line indicate the presence of a tricritical point at or very near the NAC multicritical point. No thermal indications for a biaxial nematic phase were observed.