Supramolecular Liquid Crystals Induced by Hydrogen-Bonding Interactions between Non-Mesomorphic Compounds. II. Effect of Lateral Substitution

Abstract

Two groups of the laterally methyl-substituted 1:1 associates between 4-(4′-pyridylazo-3-methylphenyl)-4″-substituted benzoates and 4-substituted benzoic acids were prepared to investigate the effect of different substituents, either on the pyridine-based derivatives or on the acid component, on the extent and stability of the supramolecular liquid crystal phases induced by intermolecular hydrogen bonding. In the first series of complexes (Group A), the non-mesomorphic pyridine-based derivative carries, in addition to the lateral methyl group, a terminal polar substituent, whereas the benzoic acid component, which is mesomorphic, carries an alkoxy group of varying chain length. The other series of complexes (Group B) is composed of the same pyridine-based derivatives, but the benzoic acid carries a small compact polar group. The complexes prepared in both series were characterized for their mesophase behavior by differential scanning calorimetry (DSC), and polarized light microscopy (PLM). Six pyridine-based derivatives, with molecular formula 4-X-C6H4COOC6H3(3-CH3)-N=N-C5H4N, were prepared. The substituent, X, varies between CH3O, CH3, H, Cl, Br, and CN. The smectic C mesophase is observed in most of group A complexes, and the nematic phase is the mesophase induced in some of group B complexes.