TEMPERATURE DEPENDENT PITCH IN CHOLESTERIC PHASE

Orientational ordering in the cholesteric liquid crystal is investigated theoretically by assuming the intermolecular force as the sum of a repulsion of hard-core with shape of twisted rod and of dispersion forces of Maier-Saupe type and of Goossens type. A method of symmetry breaking potential is applied to obtain the free energy as a function of the order parameter and the pitch in the helical structure. Thus, the clearing temperature and the pitch are calculated as functions of the parameters involved in the intermolecular force. By comparing with the results of calculation, one can understand the temperature dependence of the pitch and also the relation between the optical activity and the pitch observed in some cholesteric liquid crystals.