Role of molecular structural flexibility on mesomorphism

• Published in: Molecular Crystals and Liquid Crystals 2017-01, Vol.642 (1), p.1-8
• Main Authors: Pandya, S. H., Patel, V. R.
• Format: Article
• Language: English
• Subjects: Chalconyl ester; Crystals; enantiotropic; Homology; Liquid crystals; mesomorphism; Molecular structure; Nematic; smectic; Surface layer; Texture; Thermal stability
• ISSN: 1542-1406; 1563-5287; 1527-1943
• DOI: 10.1080/15421406.2016.1190139

A homologous series of novel chalconyl ester derivatives: RO.C 6 H 4 .COO.C 6 H 4 .CO.CH:CH.C 6 H 4 .OC 6 H 13 (n) shave been synthesized and studied for its thermotropic liquid crystal (LC) properties with a view to understanding and establishing the relation between molecular structure and LC properties. The homologous series consists of eleven members whose, mesomorphism commences from C 3 of the series and continues up to the C 16 homologue. The C 1 and C 2 homologues are nonliquid crystals. All the LC homologues are enantiotropically nematogenic with absence of smectogenic character. Transition temperatures were determined by an optical polarizing microscope (POM) equipped with a heating stage. Textures of a nematic phase are threaded or Schlieren. Analytical and spectral data confirms the molecular structures of homologues. Transition curve Cr-N/I behaved in normal manner. N-I transition curve exhibits an odd even effect; descended at C 10 homologue and then again rises at C 12 and descended from and beyond C 12 homologue. Thus it partly deviates from normal behaviour. Thermal stability for nematic is 95-89°C and nematogenic upper and lower mesophase lengths are 41.0°C and 07.0°C respectively. Group efficiency order for nematic on the basis of thermal stability is -OC 8 H 17 (n)> -OC 6 H 13 (n) > -OC 10 H 21 (n) and it is a low order melting type series.