Synthesis and Evaluation of Liquid Crystalline Properties of a Novel Homologous series:α-3-[4'-w-Alkoxy Benzoyloxy] Phenyl-β-4'-Nitro Benzoyl Ethylenes

摘要

The titled homologous series consists of 11 members. The methyl and ethyl homologues are nonmesomorphic because of very high melting points, however, the propyl to hex-adecyl derivatives are enantiotropic nematic with absence of smectogenic. The texture ofnematic mesophase is threaded or Schlieren. The nematic-isotropic transition curve of the phase diagram behaves in a normal manner with the exhibition of an odd-even effect. The transition temperatures of the series and liquid crystal properties are observed through optical polarizing microscopy and a hot stage. The novel materials were characterized by elemental analysis, infrared, and 'H NMR spectroscopy. Analytical data support the molecular structures. The liquid crystal properties of the novel series are compared with structurally similar homologous series. The novel series is entirely nematogenic with absence of smectic character and of a middle-ordered melting type. The nematic-isotropic thermal stability varies between around 120° C and 180°C.