A new mesomorphism of the alkyl 4-(2-perfluoroalkyl)ethoxybenzoate derivatives

The liquid-crystalline properties of the homologous members of alkyl 4-(2-perfluorooctyl)ethoxy-3-R-benzoates (R = H (1), NO2 (3), Br (4)) show a new mesomorphic behavior. The lower alkyl (methyl-pentyl) esters of 1 exhibit a smectic A phase, and the smectic A-isotropic transition temperature tends to decrease with increasing the carbon number of the alkyl group, where the layer spacing of the smectic A phase tends to become short with increasing carbon chain length. The hexyl-decyl esters are non-mesogenic, and the after members again show a smectic A phase. The similar trend has been found for 3 and 4. Homologous members of alkyl 4-(2-perfluorodecyl)ethoxybenzoates (2) also show a similar thermal behavior. The smectic properties are strongly dependent on the relative constitution of the perfluoroalkyl group to the alkyl one within the molecule. The molecular arrangement of the smectic A phase is discussed.