In this research, the unique technique of differential ac free- standing film calorimetry is used to measure the heat capacity of free-standing liquid crystal films and other liquid crystal mesophases. This technique allows investigation of two-dimensional physical phenomena without the complicating effects of a substrate. Because of its extremely high resolution (better than 1 in 100,000), it is possible to obtain high-quality heat capacity data from the two-layer films, and acquire information on unexpected layer-by-layer transition sequence near the smectic-A-hexatic B transition of several liquid crystal compounds. In addition, high- resolution optical reflectivity experiments (better than 5 in 10,0000) are coupled to the calorimetric measurements to allow simultaneous measurements of heat capacity and optical reflectivity of various liquid films and other liquid crystal mesophases. The proposed work will enable one to test important theoretical predictions related to the Kosterlitz-Thouless-type transition in two dimensions, and will provide new insights into the physics of two-dimensional substrate-free systems. %%% A state of art differential ac calorimeter developed in this research is used to measure the heat capacity of free-standing liquid crystal films (similar to soap films on a ring) as thin as two molecular layers. This unique technique offers new opportunities to investigate several critical two-dimensional physical phenomena without the complicating effects of a substrate.
