Molecular structure and mesomorphism: Effect of tail/lateral group

• Published in: Molecular Crystals and Liquid Crystals Vol. 630; no. 1; pp. 58 - 68
• Main Authors: Sharma, Vinay S., Patel, R. B.
• Format: Journal Article
• Language: English
• Published: Philadelphia Taylor & Francis 02.05.2016; Taylor & Francis Ltd
• Subjects: Crystallography; Heating; Homology; Liquid crystals; mesogen; Mesomorphic; Molecular structure; nematic; odd-even effect; Phase transformations; smectic; Surface layer; Texture; Threaded
• ISSN: 1542-1406; 1563-5287; 1527-1943
• DOI: 10.1080/15421406.2016.1146866

Chalconyl homologous series of novel mesogenic substances of molecular structure RO-C 6 H 4 -COO-C 6 H 4 -CO-CH:CH-C 6 H 4 -OC 16 H 33 (P) has been studied with a view to understanding and establishing the effects of molecular structure on liquid crystal (LC) properties. A novel homologous series consists of 13 (C 1 to C 18 ) members. C 1 to C 5 and C 7 members are non-mesogenic and the even numbered C 6 to C 18 homologues are enantiotropically nematogenic with absence of smectogenic property. Thermotropic properties such as phase transition temperatures and textures (threaded or Schlieren) were determined by an optical polarizing microscopy equipped with a heating stage. Analytical and spectral data confirm the molecular structure. Transition curves (Cr-N and N-I) showing phase behaviors in phase diagrams behave in a normal manner except C 16 and C 18 homologues, which partially deviate from normal behavior in N-I transition curve. Thermal stability for nematic on average is 113.14°C and the total mesophase length ranges from 10 to 26°C. The usual odd-even effect is absent for the N-I transition curve. The LC properties of the present novel series are compared with structurally similar known series. The present novel series is predominantly nematogenic without exhibition of smectogenic character, and is of a lower middle-ordered melting-type.