Accepted Friday Aug 28, 2009
This report reviews nearly 20 years of research related to antiferroelectric liquid crystals, and gives a short overview of possible applications. The antiferroelectric liquid crystals are the common name for smectic liquid crystals formed of chiral elongated molecules, exhibiting number of smectic tilted structures with strong tilt azimuthal direction variation from the layer to the layer (i.e. non synclinic structures). The phases have crystallographic unit periodicity ranging from few (SmC*a), four (SmC*FI2), three (SmC*FI1) and two (SmC*A) smectic layers and all of the phases posses liquid like order inside the layer. The overview describes the discovery of phases and various methods used for their identification, their structures and properties. Also theoretical understanding of these systems is given; one of the models - the discrete phenomenological model of antiferroelectric liquid crystals is discussed in details as this model allows for the most experimentally consistent explanation of phase structures and observed phase sequences under changes of temperature or external fields.