Liquid Crystals VIII. The Mesomorphic Behavior of Some Optically Active Aromatic Schiff's Bases

Abstract

Abstract A series of optically active aromatic Schiff's bases containing p-alkoxy and p-acyloxy groups were prepared and their mesomorphic properties were studied. Chirality was achieved by introducing an asymmetric carbon atom into the hydrocarbon chain of either the alkoxy or acyloxy group. Thus, 4-active-alkoxybenzylidene-4′-aminophenyl acylates, 4-active-alkoxy-benzylidene-4′-aminobenzonitriles and bis-(4′-active-alkoxybenzylidene)-2-chloro-1,4-phenylenediamines were synthesized. Most of the compounds exhibited both smectic and cholesteric mesomorphism. Several compounds showed only cholesteric behavior. For example, S(+)-4-methoxybenzylidene-4′-aminophenyl p-methylpentanoate was cholesteric between 41 and 78°C. By comparison, the racemic mixture of R and S enantiomers of this compound was nematic between 36 and 78°C.