Abstract
The phase behavior near the nematic–smectic-A–smectic- (N–Sm-A–Sm-) point has been studied with a high-resolution ac calorimetry technique in seven binary mixtures of two chiral compounds. The smectic-A (Sm-A)–smectic-(Sm-) phase transitions are continuous for all the mixtures studied. The Sm-A–Sm- specific-heat variations are well described by the extended Landau model, with the possible exception of the mixture closest to the N–Sm-A–Sm- composition. As the N–Sm-A–Sm- point is approached, the Sm-A–Sm- transition became more tricritical-like, indicating that the tricritical point (TCP) is located at or very near the N–Sm-A–Sm- point. These observations contradict a previous report that the Sm-A–Sm- TCP is displaced from the N–Sm-A–Sm- point in this system. Anomalous variations in the N range suggest a restructuring that might be associated with biaxial nematic fluctuations.
- Received 11 May 1990
DOI:https://doi.org/10.1103/PhysRevA.42.6087
©1990 American Physical Society