The pre-transitional effect in antiferroelectric liquid crystals: a comparison between theory and experiment

We have investigated, experimentally and theoretically, the low field (pre- transitional) behaviour of an AFLC material. By measuring the light transmi ssion through a device between crossed polarizers, as a function of both or ientation and applied voltage, we determine the variation of both the effec tive optic axis tilt angle phi and the optical anisotropy Delta n as a func tion of voltage. In order to model this behaviour we use an order parameter theory based on changes to the distribution of molecules within the AFLC l ayers rather than the soft mode description. With this model we have been a ble to describe the observed tilt and anisotropy behaviour.