Mesomorphic and electro-optical properties of new achiral banana-shaped molecules

Two new series of achiral banana-shaped molecules have been prepared. Their mesomorphic, electrooptical and structural properties have been investigat ed. The first series of hydrogenated molecules shows the nematic phase with short chains (n=8-10), N and SmC phases with intermediate chain lengths (n =11-13) and SmC plus an unknown smectic phase with long chains. The second series of fluorinated molecules is more peculiar, exhibiting four disordere d smectic phases. Two of these have broken fan-shaped or schlieren optical textures like the SC phase, whereas the two others show slightly different textures with more or less mosaic domains. These phases display various swi tching characteristics, including but not limited to the "antiferroelectric " one reported for the Niori series. The relation between molecular structu re and mesomorphic properties is discussed.