New switchable smectic phases in banana-shaped compounds

A new series of achiral compounds with banana-shaped molecules ('E-n') has been synthesized and studied by the classical techniques (optical microscop y, differential scanning calorimetry, X-ray diffraction, miscibility studie s and electro-optic investigations). The short homologues (E-7-E-10) give s witchable smectic mesophases. Nevertheless their textures clearly differ fr om those of the B2 mesophase. In addition, the E-10 compound displays a sme ctic polymorphism involving a new bilayered structure.