Microcalorimetric study of nematic-to-neat-soap and nematic-to-isotropic phase transitions in a lyotropic liquid crystal

The results of specific-heat measurements at the nematic- (N) to-neat-soap (NS) and nematic-to-isotropic (I) phase transitions in binary mixtures of cesium-perfluoro-octanoate and water are reported. The ratio of specific-heat amplitudes above and below the N-NS transition, ${\mathrm{A}}^{+}$/${\mathrm{A}}^{\mathrm{-}}$, and the specific-heat exponent α remain ∼1.0 and ≤0.02, respectively, suggesting 3D XY-type behavior. At the first-order N-I transition, vanishing latent heat and coexistence range at low concentration indicate the existence of a Landau point.