Role of n-alkoxy terminal end groups on mesomorphism

A homologous series RO-C₆H₄-CH:CH-COO-C₆H₄-CO-CH:CH-C₆H₄-OC₆H₁₃ (n) of novel liquid crystals (LC) has been synthesized and studied with a view to understanding and establishing the relation between molecular structure of a substance and the LC properties or behavior of thermotropic LC materials. Novel series consist of 11 homologues. C₁ and C₂ homologue derivatives are non-LCs and the rest of homologues (C₃ to C₁₆) are nematogenic without exhibition of smectic property. Transition temperatures were determined by an optical polarizing microscopy equipped with a heating stage. Transition curve Cr-N/I of a phase diagram behaved in normal manner. N/I transition curve partly deviated at C₆ and C₁₀ homologues from normal descending behavior, and exhibited very narrow and sharp odd-even effects. Textures of nematic phase are threaded or Schlieren. Thermal, analytical, and spectral data confirmed the molecular structures of novel chalconyl ester derivatives. Thermal stability for nematic is 95.77°C and the upper and lower mesophase lengths vary from 35 to 16°C at C₅ and C₈ homologues respectively. Group efficiency order derived for nematic on the basis thermal stability is -OC₁₀H₂₁ (n) > -OC₈H₁₇(n) > -OC₆H₁₃(n).