A Novel Homologous Series of Thermotropic Mesogens of Ethylene Derivatives: α-4-[4′-n-Alkoxy Benzoyloxy] Phenyl β-4^″Methoxy Benzoyl Ethylenes

Abstract

A novel homologous series consists of 12 compounds. The shorter chain homologues do not show liquid crystal phases, but from six carbons onwards, the nematic phase is exhibited enantiotropically, with some members also showing a smectic phase. The phase behavior of the transition curves of the series shows a usual trend. The texture of the nematic phase is the threaded or Schlieren type and that of smectic phase is a smectic A. An odd–even effect is observed for smectic–nematic and nematic–isotropic transition curves. Analytical data confirm the molecular structure. The transition temperatures were determined by an optical polarizing microscopy. The mesogenic properties of the novel series are compared with a structurally similar homologous series. The average smectic–nematic and nematic–isotropic thermal stabilities are 133.4°C and 159.8°C, respectively, with a mesogenic temperature range of 10°C to 62°C.