Ferroelectric properties exhibited by mesophases of compounds composed of achiral banana-shaped molecules

The synthesis and mesomorphic properties of a new series of five-ring esters composed of banana-shaped molecules are reported. The homologues containing n-dodecyloxy, n-tetradecyloxy and n-hexadecyloxy terminal chains exhibit a smectic phase while that with an n-octadecyloxy chain shows a two-dimensional structure. The structures of the mesophases have been determined by X-ray diffraction studies. Interestingly both these mesophases exhibit ferroelectric properties. The electro-optical switching characteristics have been investigated using both triangular-wave and d.c. electric fields. Ferroelectricity is clearly demonstrated in both the mesophases by bistable switching behaviour.