Ferroelectric liquid crystals

A review is given of practically all the theoretical and experimental results on ferroelectric liquid crystals based on chiral smectics with molecular tilt. The symmetry aspects of the problem are examined, and the fundamentals of the phenomenological theory are discussed. The microscopic approach to the description of the dipolar ordering in tilted smectics is set forth, and several molecular models are considered. The critical behavior of a liquid crystal at the second-order transition between the smectic A and smectic C phases is also discussed. Considerable space is devoted to considering the relationship between the actual structure of the molecules and the size of the spontaneous polarization and to discussing the behavior of ferroelectric liquid crystals in various external fields. Data are presented on the physical parameters of the known liquid-crystal ferroelectrics. The article concludes with a discussion of the possibilities for practical application of ferroelectric liquid crystals.