A Molecular Theory of Chiral Smectic C iquid Crystals I

Abstract

A molecular theory of chiral smectic C liquid crystals is formulated. On the basis of molecular field theories of smectic A and cholesteric liquid crystals. Landau free energy associated with tilt and twist deformations of director is obtained from a microscopic point of view. Then the temperature dependences of the tilt angle and the helical pitch in chiral smectic C and cholesteric phases are numerically calculated. One finds the qualitative agreement between the present theoretical result and the experimental findings for the critical exponent of the tilt angle but not for that of the helical pitch. In addition it is also pointed out that the temperature dependence of orientational order is significant to drive chiral smectic C-smectic A phase transitions, rather than that of translational order.