New mesogenic compounds with unconventional molecular structures 1,2-Phenylene and 2,3-naphthylene bis[4-(4-alkoxyphenyliminomethyl)benzoates] and related compounds

Abstract

DSC and X-ray studies on a series of 1,2-phenylene bis[4-(4-alkoxyphenyliminomethyl)benzoates] are presented. The phases were shown to be classical nematic and/or smectic by their continuous miscibilities with reference mesophases. The layer spacings in the smectic A phase measured as a function of the alkyl chain length revealed that the mean tilt angle of the linear three-ring part of the molecule to the layer normal is about 37° and that the molecular core is V-shaped with an angle of about 70° between the two out-stretched benzoate legs. This molecular model accounts for the effects of a methyl group introduced into the 3- or 4-position of the 1,2-phenylene moiety on the mesomorphic properties. Both the nematic and smectic A properties are markedly promoted by replacement of the 1,2-phenylene group by the 2,3-naphthylene group.

The phases exhibited by the less-elongated series of 2,3-naphthylene bis(4-alkoxybenzoates) are also nematic and/or smectic A, but are now monotropic. The formation of stable smectic A and metastable B phases by a series of 1,2,3-tris[4-(4-alkoxybenzylideneamino)benzoyloxy]benzenes is described.