New achiral non symmetric banana-shaped mesogens: Mesomorphic and electro-optical properties

The first series of achiral nonsymmetric banana-shaped mesogens has been sy nthesized. The mesophases observed for these compounds depend on the whole number of carbons in the alkyl chains (N). They were investigated by optica l microscopy, calorimetry, X-ray diffraction experiments and electro-optica l measurements. For intermediate and long chains (N greater than or equal t o 20) the liquid crystal phase is smectic (Sm?) and for shorter chains (N < 20) the mesophase appears to be columnar ordered (Col?). Yet the structure of neither one is fully resolved. Both phases exhibit a ferroelectric beha viour.