Abstract
It is generally believed that monomeric p-disubstituted benzenes are not mesogenic. However, studies on binary systems with nematogenic N-(4-propoxybenzylidene)-4-hexylaniline revealed that various p-disubstituted benzenes are potentially smectogenic. Employing NHCOCnH2n+1 or CONHCnH2n+1 group, which favors particularly the high transition temperatures to latent smectic phases, the author succeeded in designing discogenic or nematogenic benzene derivatives; e. g. N, N′-dialkanoyl-2-methyl- and 2, 4, 6-trimethyl-1, 3-benzenediamines, N, N′, N″-trialkyl-1, 3, 5-benzenetricarboxamides, N, N′-dialkanoyl-2, 5, 6-trimethyl-4-alkanoyloxy-1, 3-benzenediamines, N, N′-dialkanoyl-2, 4-bis (alkanoyloxy)-1, 3-benzenediamines, and N, N′-dialkanoyl-2, 3, 5, 6-tetrakis(alkanoyloxy)-1, 4-benzenediamines. Thus, the anisotropy of the intermolecular forces, which is the primary factor in the formation of liquid crystals, was shown to be achievable irrespective of molecular shape. Liquid crystals may be discotic if the rotation around the short axis perpendicular to the molecular plane is easier than that around the long axis in the plane.
