Mesomorphic, electro-optic and structural properties of binary liquid crystalline mixtures with ferroelectric and antiferroelectric liquid crystalline behaviour

摘要

Two new binary liquid crystalline mixtures composed from the chiral liquid crystalline materials with partially fluorinated non-chiral chain and without lateral substitution at the molecular core have been designed and investigated by polarisation optical microscopy, differential scanning calorimetry, broad-band dielectric spectroscopy, and X-ray techniques. Both mixtures possess the paraelectric orthogonal smectic A*, the tilted ferroelectric smectic C* and the antiferroelectric smectic C-A* phases over a reasonably broad temperature range. The gained results reveal a considerable improvement of (i) the broadness of the mesophases temperature range of the ferroelectric and antiferroelectric phases (up to 130 K breadth) and (ii) electro-optical properties, namely the spontaneous polarisation (up to 200 nC/cm(2)) and tilt angle (higher than 40(o)), with respect to that of the original pure compounds.