Heat capacity studies near the smectic A-smectic C (smectic C*) transition in a racemic (chiral) smectic liquid crystal.

Both chiral and racemic versions of 2-methylbutyl 4'-n-pentyloxy- biphenyl-4-carboxylate (2M45OBC) exhibit smectic A and smectic C phases. Both smectic-A-smectic-C and smectic-A-chiral smectic- C transitions are found to be mean-field like with a large sixth order term in the Landau free energy expansion. Our results also shed light on similarities and differences between the chiral and racemic compounds. For example, the SA-SC* transition temperature is slightly higher than the Sa-SC* transition temperatures. This may be due to a coupling between the molecular tilt of the C* phase and macroscopic polarization due to the optical activity.