ABSTRACT
A Novel homologous series of liquid crystals, viz, α-4(4’-n-alkoxy cinnamoyloxy) benzoyl-β-4”-pentyloxy phenyl ethylene, has been synthesized. The series consists of eleven homologs. The methyl to pentyl derivatives are not liquid crystalline and the rest of the homologs are enantiotropic liquid crystals. The decyl and dodecyl derivatives of the series are enantiotropically smectogenic in addition to nematogenic in character, but the hexyl, tetradecyl and hexadecyl homolog derivatives of the series are only nematogenic without the exhibition of a smectic phase. The transition temperatures of the novel substances were determined by optical polarizing microscopy equipped with a heating stage. A plot of transition temperatures versus the number of carbon atoms present in the n-alkoxy terminal chain represents the phase behavior of the series. An odd-even effects not observed for the nematic-isotropic transition curve. The textures of the nematic phase are of a threaded or Schlieren type and those of the smectic A and smectic C phases are typical. Analytical and spectral data agree with the molecular structures. The smectic and nematic thermal stabilities are 122 °C and 157 °C, respectively. The smectic phase commences from the decyl homolog. Smectogenic phase lengths vary from 13 °C to 15 °C and the nematogenic phase lengths vary from 11 °C to 46 °C. The series is predominantly nematogenic and partly smectogenic with considerable mesophase length and a middle-ordered melting type. The liquid crystal properties of the present series are compared with structurally similar homologous series.
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