Liquid Crystal Formation in Binary Systems. VIII. Induction of Smectic Phases by the Addition of 4-Alkoxynitrobenzene or 4-Alkoxybenzonitrile to N-(4-Propoxybenzylidene)-4-hexylaniline

Abstract

Abstract When 4-alkoxynitrobenzenes are mixed with N-(4-propoxybenzylidene)-4-hexylaniline, smectic A phases which are not found with the component compounds, are produced. The liquid crystals are stable if the number of carbon atoms in the alkoxyl group is eight or more, the maximum temperature being 49 °C with dodecyloxyl group, but they are entirely metastable if the number of carbon atoms is six or less. The extrapolation of the partly-observed smectic A-isotropic transition point curve indicates that 4-(dodecyloxy)nitrobenzene has a latent transition point at about −25 °C and that all the examined p-disubstituted benzenes are potentially smectogenic. Smectic A phases are also induced by the addition of 4-alkoxybenzonitriles to the above Schiff base. The transition to the induced mesophase is enantiotropic when the alkoxyl group is decyloxyl or dodecyloxyl. The replacement of the propoxyl group in the Schiff base with an ethoxyl group makes the induced smectic A phases thermally less stable. The change is drastic when the alkoxyl group in the p-disubstituted benzene is hexyloxyl or shorter.