Molecular Crystals and Liquid Crystals, Vol.630, No.1, 130-138, 2016
Dependence of thermotropic mesomorphism on flexible tail group
A novel homologous series RO-C6H4-COO-C6H4-CO-CH:CH-C6H4-OC12H25 of chalcones have been synthesized and studied with a view to understand and establish the effects of molecular structure on liquid crystal (LC) properties of a substance. Liquid crystal properties of a novel series commences from C-6 homologue and continue upto the last C-18 homologue derivative of a series, as enantiotropically nematogenic without exhibition of smectogenic characteristic. The rest of the homologues (C-1 to C-5) are nonliquid crystals (NLC). Transition temperatures of homologues (C-1 to C-18) are determined by an optical polarizing microscopy equipped with a heating stage. Textures of a nematic phase are threaded or schlieren. Transition curves of a phase diagram behaved in normal manner except for C-18 member of a series, which drastically behaved with abnormal manner. N-I transition curve exhibits odd-even effect. Average thermal stability for nematic is 110.25 degrees C and mesophase length ranges from 10 degrees C to 39 degrees C. Analytical and spectral data supported the molecular structures of homologues. LC properties of present novel series are compared with structurally similar other known homologous series. Thus, present novel series of chalcones is partly nematogenic and of middle-ordered melting type.