Novel Nematogenic Benzene Derivatives: N,N′-Dialkanoyl-2,5,6-trimethyl-4-alkanoyloxy-1,3-benzenediamines

Abstract

Abstract A series of N,N′-dialkanoyl-2,5,6-trimethyl-4-alkanoyloxy-1,3-benzenediamines has been synthesized. The mesophases appearing in the octanoyl to octadecanoyl derivatives adopt a schlieren texture and are transformed into isotropic liquids, with enthalpy changes as small as from 1 to 4 kJ mol−1. Their X-ray diffraction patterns consist of only two diffuse peaks, fully confirming that the phases are nematic in type. The spacing deduced from the inner diffraction peak is markedly shorter than the molecular length and is similar to the spacings, d100, found for the hexagonal disordered columnar phases exhibited by closely-related benzene derivatives. This is strong evidence for the alignment with their normals to the average molecular planes parallel. In other words, the mesophase is classified as discotic even though the molecular shape is far from disk-like. Another viscous birefringent phase is found below the nematic phase when the molecule carries octanoyl to hexadecanoyl groups.