Liquid Crystal Formation in Binary Systems. II. Induction of Nematic and Smectic Phases by Electron Donor-Acceptor Interaction between the <i>p</i>-Dimethylamino and <i>p</i>-Nitro Derivatives of <i>N</i>-Benzylideneaniline

Abstract

Abstract The formation of solid molecular complexes and the induction of nematic and smectic phases have been demonstrated with a number of binary mixtures of potentially-mesomorphic electron donors and acceptors of the type N-(p-X-benzylidene)-p-Y-aniline. One of the components contains a dimethylamino group as X or Y, and the other a nitro group as X or Y. The remaining substituents are methoxyl, ethoxyl, or propoxyl groups. The maximum temperature of the nematic phase induced in these electron donor-acceptor systems is higher by 23 to 45 °C than the straight line joining the latent transition temperatures of the two components. The tendency to form a solid complex and that to induce a nematic phase are both shown to a large extent by the propoxy derivatives, to a lesser extent by the methoxy derivatives, and least by the ethoxy derivatives. All the solid molecular complexes are reddish brown and exhibit an additional electronic absorption band located at about 500 nm. The mesophases are similarly colored. The enhanced thermal stability of the nematic and smectic phases in these binary mixtures is ascribed to the complex formation by an electron donor-acceptor interaction.