Synthesis and Liquid Crystal Properties of Novel Ethylene Derivatives: α-3-[-4′-n-Alkoxy Cinnamoyloxy] phenyl β-4′′-methoxy Benzoyl Ethylenes

Eleven members of a novel homologous series of α-3-[-4′-n-alkoxy cinnamoyloxy] phenyl β-4′′-methoxy benzoyl ethylenes were synthesized. The methyloxy, ethyloxy, butyloxy, and hexadecyloxy homologues are nonmesomorphic, while all the other homologues are mesomorphic. The mesomorphic homologues are enantiotropically smectogenic in combination with nematogenic character, except for the propyloxy homologue, which shows only nematogenic character. A phase diagram of the series shows the expected mesomorphic behavior. Transition temperatures of this series are observed through an optical polarizing microscope equipped with a heating stage. An odd–even effect is observed for nematic–isotropic transition curve. Analytical data supports the structures of the molecules. Mesomorphic temperature range varies from 23°C to 51°C. Liquid crystal properties of this series are compared with a structurally similar homologous series. The smectic and nematic thermal stability of the series are 138.8°C and 165.7°C, respectively. The nematic phase shows a threaded or schlieren texture, and the smectic phase is a smectic A phase.