Dependence of liquid crystallinity on molecular rigidity

A novel homologous series of liquid crystals (LC) of chalconyl derivatives is synthesized and studied with a view to understanding and establishing the effects of molecular structure on liquid crystal properties. The novel series consists of 12 homologues. Nematogenic LC property commences from C₃ and continues up to C₁₄ and the smectogenic mesophase is exhibited from C₄ to C₁₆. The C₃ homologue is a monotropic nematic and the rest of the homologues are enantiotropically smectic and nematic or only smectic (C₁₆). Transition curves Cr-Sm, Sm-N, Cr-I, and N-I behave in normal manner with exhibition of odd-even effect, showing phase behaviors of the series.