Twist grain boundary and antiferroelectric smectic C* phases in a new chiral compound

During the last five years, two new liquid crystalline structures have been obtained with chiral molecules: antiferroelectric smectic C* and Twist Grain Boundary (TGB) smectic phases have received much attention as materials for fundemental studies and for display device applications. Up to now, these two phases have rarely been observed in the same pure compound. In this paper we report the synthesis and studies of a new chiral tolane having the formula: [GRAPHICS] It presents for the first time the new TGB(C) and antiferroelectric mesophases. Optical microscopic observation and DSC show the sequence: CrSCA* S-CFI* S-C* TGB(C) TGB(?) N* BP I The low temperature TGB(C) phase was identified by miscibility studies with the well known compound 12F(2)BTFO(1)M(7) [10] and by X-ray diffraction. The pitch values of the different chiral phases are short and the direction of torsion of the helices of the S-C* and S-CA* phases are inverse. The electro-optical properties of these tilted phases have also been assessed in the classical SSFLC geometry.