Thermal-conductivity studies near the smectic-A–smectic-Ctransition in a liquid-crystal compound

High-resolution thermal-conductivity and heat-capacity studies were carried out on the same sample in the vicinity of the smectic-A--to--smectic-C transition of N-(4-n-heptyloxybenzylidene)-4'-n-butylaniline (70.4). The heat capacity shows a mean-field jump and can be well described by an extended-mean-field model. The thermal conductivity also shows a jump near the smectic-A--smectic-C transition. Instead of a smooth thermal diffusivity, as predicted by a conventional dynamic theory, we found both a peak and a dip in the thermal diffusivity near the transition temperature.