Critical behavior of thermal parameters at the smectic-[Formula presented]–hexatic-[Formula presented] and smectic-[Formula presented]–smectic-[Formula presented] phase transitions in liquid crystals

High temperature resolution measurements of thermal conductivity, thermal diffusivity, and specific heat, with simultaneous polarized light visual inspection of the sample, have been performed at two different liquid crystal phase transitions: the [Formula presented] (Smectic-[Formula presented]–Smectic-[Formula presented] and the [Formula presented] (Smectic-[Formula presented]–hexatic-[Formula presented] in racemic A7 [4-(3-methyl-2-chlorobutanoyloxy)-[Formula presented]-heptyloxybiphenyl] and 65OBC [Formula presented]-hexyl-[Formula presented]-pentyloxybiphenyl-4-carboxylate) compounds, respectively. In the past, anomalies in the thermal conductivity at the transitions have been reported. Our results indicate a nonsingular behavior of the thermal conductivity at both transitions, similarly to what has been previously reported for the smectic-[Formula presented]–nematic phase transition. It is also shown how, in several cases, the nature of the transition can be affected by the sample thermal history due to the presence of strain annealing phenomena.