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ABSTRACT
A novel thermotropically mesomorphic, meta-substituted nitro group of chalconyl ester series, RO-C6H4-COO-C6H3-(NO2)-CO-CH=CH-C6H4OC12H25(n) (para) is synthesized and studied with an aim to establish the relation between molecular structure and the mesomorphism with reference to changing molecular flexibility in presence of nitro lateral group. Novel homologous series consist of thirteen homologs (C1–C18) whose mesomorphism commences from C5 homolog as enantiotropic nematogenic with absence of smectic property, even in the monotropic condition. Transition temperatures of novel substances were determined by an optical polarizing microscope, equipped with a heating stage (POM). Textures of a nematic phase are threaded or Schlieren. N-I transition curve exhibited narrow, sharp and short odd-even effect; with deviating trend in a phase diagram. Analytical, spectral and thermal data confirmed the molecular structures of homologs. Thermal stability for nematic is 182.89°C, whose mesophase lengths minimum to maximum ranges from 17°C to 45°C and it is an upper middle ordered melting type series. Group efficiency order for nematic is series 1 > series Y > series X, as derived from comparative study of structurally similar analogous series.
Acknowledgments
Authors acknowledge thanks to the management of the college and the Head of the Chemistry Department Dr. R. B. Patel of K. K. Shah Jarodwala Maninagar Science College, Ahmedabad for their valuable cooperation in the work. Authors are also thankful to Dr. A. V. Doshi, Ex-Principal, M. V. M. Science and Homescience College, Rajkot for his co-operation, valuable suggestions, comments, and help as and when needed during the course of present investigation. Thanks are due to NFDD Centre, Saurashtra University, Rajkot for analytical and spectral services.