Synthesizes of new "bent-core" mesogens and investigation of their liquid crystalline properties

Bent mesogens, represent a topical field in current liquid crystal research and in the past few years much effort has been devoted to the synthesis and physical characterization of bent-core mesogens. Liquid crystalline molecules with a bent molecular shape, so called banana-shaped LC, have chiral superstructure, despite of the fact that the molecules themselves have an achiral configuration. These molecules can give rise to a number of different mesophases provisionally labeled as B phases. Among the B phases, electro-optical switching has been observed in the smectic B2, B5 and B7 phases. The aim of this work is the design, synthesis and characterization of new banana-shaped mesogens and their siloxane derivatives. For his purpose, bent-core compounds and their siloxane derivatives were synthesized and liquid crystalline behavior was investigated. The structures of the synthesized bent-core compounds and their siloxane derivaties were characterized by using spectroscopic methods (1H-NMR, 13C-NMR, 29Si-NMR, MS). The mesomorphic properties of the obtained new compounds were investigated using polarised light optical microscopy (PM) and differential scanning calorimetry (DSC). Keywords: Liquid Crystals, "Bent-core" Mesogens, Banana Shaped Compounds.