Abstract
ABSTRACTA novel homologous series RO-C6H4-COO-C6H3-(NO2)-CO-CH˭CH-C6H4OC18H37(n) para of chalconyl ester derivatives have been synthesized and studied with view to understanding the effect of an ortho substituted nitro group on thermotropic liquid crystal (LC) behavior. The novel homologous series consists of thirteen homologues (C1 to C18). The C1 to C4 homologues are nonliquid crystal (NLC) and the rest of the homologues (C5 to C18) homologues are enantiotropically nematogenic without exhibition of a smectic phase even in the monotropic condition. Transition temperatures were determined by an optical polarizing microscope (POM) equipped with a heating stage. Texture of nematic phase are threaded or Schlieren. Analytical, thermal and spectral data supported molecular structure of homologues. Thermal stability for nematic is 147.1°C whose mesophase lengths vary between 16.0 and 32.0°C the C7 and C18 homologues, respectively, and their mesogenic exhibition range between 96.0 and 166.0°C. Thus, the present novel series is middle ordered melting type, Group efficiency order is derived from comparative study of structurally similar series. The transition curves of a phase diagram behaved in normal manner except C10 and C16 homologues. Odd-even effect is observed for N-I transition curve. Group efficiency order derived is: -OC12H25 (n) > -OC18H37 (n) > -OC18H37 (n).
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