Molecular Crystals and Liquid Crystals, Vol.607, No.1, 104-113, 2015
The Relation Between Mesomorphism and Molecular Structure of a Novel Azoester Series Involving Laterally Substituted Chloro Groups
A novel azoester homologous series 4-(4 '-n-alkoxy benzoyloxy) phenyl azo 2(''),6('')-dichloro benzene is synthesized and studied with a view to understand and establish the effects of molecular structure on liquid crystal behavior of a substance with reference to steric hindrance. The novel homologous series consists of twelve homologues. Mesomorphism commences from the heptyloxy homologue and continues up to the hexadecyloxy homologue as a monotropic nematic without the exhibition of any smectogenic characteristics. Transition temperatures were determined by an optical polarizing microscopy equipped with a heating stage. Transition curves of the phase diagram behave in a normal manner. The isotropic-nematic transition curve shows an odd-even effect in the very short range of temperature. The texture of nematic mesophase is threaded. Analytical and spectral data support the molecular structures of the homologues. Thermal stability is very low and the degree of mesomorphism is poor. Thus novel series is of low melting type and nematogenic only in a monotropic manner. Mesomorphic properties of the present, novel series are compared with structurally similar other known series.