Two Liquid Crystal Phases with Nematic Morphology in Laterally Substituted Phenylenediamine Derivatives

Abstract

Abstract Bis-(4′-n-alkoxybenzal)-2-chloro-1, 4-phenylenediamines and bis- (4′-n-alkoxybenzal)-2-methyl-1, 4-phenylenediamines with different alkoxy groups have been synthesized. Similar compounds with fluoro, bromo and chloro groups replacing the alkoxy groups have also been prepared. All the compounds show a nematic liquid phase. An additional lower temperature liquid crystalline phase is observed with chloro-substituted compounds for n-alkoxy chain lengths of C8 and longer and with the methyl substituted compounds for chain lengths of C10 and longer. This lower temperature phase can show a threaded texture very similar to the nematic phase. Furthermore, both phases can be uniformly oriented by surface action and can assume a twisted structure. We suppose that the lower temperature phase has a layered structure in which the molecules are inclined to the layers, and that it corresponds to a smectic liquid crystal classified by Sackmann and Demus as smectic C.