Study of Mesomorphism in Isomeric and Nonisomeric Linear and Nonlinear Chalconyl Series

A novel nonlinear chalconyl homologous series of ester: RO-C₆H₄-COO-C₆H₄ (m)-CO-CH:CH-C₆H₄-OC₁₆H₃₃(n) (para) have been synthesized and studied with a view to understand and establish the relation between thermotropic liquid Crystal (LC) properties and geometrically nonlinear shaped molecular structure. Homologous series consists of thirteen members ( C₁ to C₁₈) whose enantiotropic nematogenic mesomorphism commences from C₆ homologue without exhibition of smectic property. C₁ to C₅ homologues are nonmesomorphic. Transition temperatures and textures of homologues were determined by an optical polarising microscopy equipped with a heating stage (POM). Transition curves of a phase diagrams (Cr-N/I and N-I) behaved in normal manner. N-I transition curve exhibited odd-even effect. Textures of a nematic phase are threaded or schlieren. Analytical and spectral data supported molecular structures of homologues. Thermal stability for nematic is 104.5°C whose degree of mesomorphism vary minimum of 13.0°C to maximum of 37.0°C. Group efficiency order for nematic is derived by comparing present novel series with structurally analogous other homologous series. Thus, homologous series of present investigation is nematogenic with absence of smectic property and of middle ordered melting type with considerable degree of mesomorphism.