Direct transition from a nematic phase to a polar biaxial smectic A phase in a homologous series of unsymmetrically substituted bent-core compounds

Abstract

The synthesis and characterization of twenty seven new compounds belonging to three homologous series of compounds derived from 3-hydroxybenzoic acid are reported. One of the terminal positions of the constituent molecules of these compounds is substituted with a strongly polar cyano group while the other end contains an n-alkyl chain attached to a biphenyl moiety. Twenty two of these compounds show the polar partial bilayer biaxial smectic A phase which is antiferroelectric in nature. In addition, a direct transition from the nematic phase to the polar partial bilayer biaxial smectic A phase which has not been seen before is also reported. The mesophases have been characterized using polarized light optical microscopy, differential scanning calorimetry, X-ray diffraction studies and electro-optical experiments.