Heat-capacity, tilt-angle, and polarization measurements near the smectic-A–chiral-smectic-Ctransition of one liquid-crystal compound

High-resolution heat-capacity, tilt-angle, and spontaneous polarization measurements have been carried out near the smectic-A–chiral-smectic-C (SmA-Sm$C^{\mathrm{*}}$) transition of p-decyloxybenzylidene-p’-amino-1-methylpropylcinnamate (DOBA-1-MPG). The heat-capacity and tilt-angle data are well described by a mean-field model with three expansion terms. Again the ratio of the polarization (P) to the tilt angle (theta) shows a dramatic increase just below the SmA-Sm$C^{\mathrm{*}}$ transition and then remains fairly constant for $T_c$-T≳1 K. Here $T_c$ is the SmA-Sm$C^{\mathrm{*}}$ transition temperature. A mean-field model with eleven expansion terms accounts very well for this anomaly in the ratio (P/theta).