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摘要
A meta substituted chalconyl ester homologous series: ROC6H4COOC6H4(meta)COCHCHC6H4OC12H25(n)(para) is synthesized and studied with a view to understanding the effect of molecular substitution at meta position in a molecular structure on thermotropic liquid crystal properties. The novel homologous series consists of thirteen homologues (C-1 to C-18). All the homologues except the nonliquid crystal homologues C-1, C-2, C-3 are enantiotropic nematic with the absence of smectic properties. The transition and melting temperatures were determined by an optical polarizing microscopy (POM) equipped with a heating stage. Textures of a nematic phase are threaded or Schlieren. Transition curves (Cr-N/I and N-I) behave in normal manner except homologues between C-10 and C-14 of N-I curve, which show negligible deviation from normal and a smooth descending tendency. The N-I transition curve exhibits an odd-even effect up to C-10 homologue and then the odd-even effect disappears for higher homologues. Analytical and the spectral data support the molecular structures. Thermal stability for nematic is 107.3 degrees C and the mesophase lengths range between 13.0 degrees C and 35.0 degrees C at the C-18 and C-12 homologues respectively. Group efficiency order for nematic is derived on the basis of thermal stability as OC12H25(n) (linear) > OC12H25(n) (nonlinear) > OC16H33 (nonlinear).
- 出版日期2017
