Novel type of antiferroelectricity in the hexatic smectic I A* phase

In the binary system of MHPOBC and another antiferroelectric liquid crystal, we have confirmed that not only the antiferroelectric smectic I-A* (SIA*) phase but also the ferroelectric smectic I* (SI*) phase sometimes emerges below the antiferroelectric smectic C-A* phase, and that even the phase transition from SIA* to SI* may occur on cooling. The results have been discussed in connection with the origin of SIA* antiferroelectricity, i.e. a group of transverse dipoles interacting with one another between adjacent layers.