Study of Molecular Structure, Mesomorphism and Their Relation with Molecular Rigidity-Flexibility

ABSTRACT

Entirely smectogenic novel chalconyl homologue derivatives of thermotropic liquid crystals (LC) have been synthesized with a view to understanding and establishing the effects of molecular structure on liquid crystal properties and the degree of liquid crystallinity. The homologous series consists of 12 (C₁ to C₁₆) homologues with absence of nematogenic character throughout the present series. The textures of smectic phase are fan shaped or batonnet type of smectic-A or of smectic-C. Phase transition temperatures and thermotropic data were determined by an optical polarizing microscope equipped with a heating stage. The smectic–isotropic (Sm-I) phase transition curve and the Cr-Sm transition curve behave in normal manner in the phase diagram. Analytical and spectral data confirm molecular structures of novel homologues. The average thermal stability for smectic is 139.42°C and the mesogenic phase length ranges from 3.5°C to 79.6°C. Mesogenic properties are compared with the structurally similar known series.

KEYWORD:

• Liquid crystal
• mesogenic
• nematogenic; smectic

Acknowledgments

Authors acknowledge thanks to the Department of Chemistry (DST-FIST Funded & UGC-SAP Sponsored), Saurashtra University, Rajkot, for research work. Authors are also thankful to Dr. A.V. Doshi, Ex. Principal, M.V.M. Science and Home Science College, Rajkot, for his valuable co-operation during present investigation as and when needed. Also thanks are due to the National Facility for Drug Discovery through New Chemical Entities (NCE's), for analysis of samples.