Thickness-dependent smectic-A-smectic-C* transition in chiral smectic free-standing liquid-crystal films.
We have conducted heat-capacity measurements near the smectic-A -smectic-C* phase transition in free-standing films of a chiral liquid-crystal compound. The heat-capacity behavior confirms the evolution of the transition in the interior layers from first to second order as a function of film thickness suggested earlier in tilt angle measurements. The asymmetry in the heat-capacity anomaly exhibits an interesting crossover in thinner films. We also observed the phase transitions leading to the crystallization to the tilted crystal-G phase in these films at lower temperatures. The surface ordering strength in these films is found to be much larger than that in other orthogonal-smectic films, which we speculate is due to the molecular tilt.
Department of Physics, National Taiwan University, Taipei 10617, Taiwan, Republic of China.
Tung-Cheng
TC
Pan
Wen-Jiunn
WJ
Hsieh
Chih-Yu
CY
Chao