Characterization of a Chiral Smectic C Liquid Crystal.

In a smectic A (SmA)-chiral smectic C (SmC*) transition, the tilt-angle and polarization are the important parameters which determine the behavior of this transition. Both high-resolution heat-capacity and almost simultaneous tilt -angle and polarization measurements have been carried out near the SmA-SmC* transition of p(n-decyloxy-benzylidene) -p-amino-(2-methyl-butyl)cinnamate (DOBAMBC). We found two important results. First, the tilt-angle data fit reasonably well with the calculated tilt-angle from the anomalous part of the heat capacity data based on the extended mean-field model suggested by Huang and Viner. This provides a strong additional support for the extended mean-field model in describing the SmA-SmC* transition. Second, the ratio P/(theta) stays fairly constant for T(,c)-T > 2 K and shows a precipitous drop near the transition temperature (T(,c)). A calculation based on a generalized mean-field model, similar to the one proposed by Zeks, is in good agreement with our result. The temperature behavior of two critical fields, an electric field (E(,U)) at which the fringe pattern disappears in increasing field and an electric field (E(,R)) at which the fringe pattern reappears in decreasing field from above E(,U), are also studied.