Effect of the transverse dipole moment on the smectic-A-smectic-C (or -chiral-smectic-C) transition.

Abstract

Calorimetric investigations have been carried out on five different liquid-crystal compounds near their smectic-A(Sm-A)--smectic-C (Sm-C) [or--smectic-${C}^{\mathrm{*}}$ (Sm-${C}^{\mathrm{*}}$)] transitions. Contrary to the previous observation, our experimental results demonstrate that the Sm-A--Sm-C (or--Sm-${C}^{\mathrm{*}}$) transition may not become first order with reducing the Sm-A phase temperature range alone. We have also found that the magnitude of the transverse dipole moment of the constituent molecules, but not the bulk polarization only, has a strong effect on the nature of these phase transitions.