Thermal Property Evolution Toward Effectively Two-Dimensional Substrate-Free Systems.

A high-resolution differential quasi-adiabatic calorimeter has been developed to investigate the physical properties of freestanding liquid-crystal films. Our recent heat-capacity studies near the smectic-A-hexatic-B transition of both 650BC and 460BC freestanding films clearly demonstrate the evolution towards two-dimensional limiting behavior in four-layer films. As the film thickness decreases towards four molecular layers, the heat-capacity anomalies first display separate peaks for the surface and interior transitions and then evolve to one dominated by the surface transition.