Symmetric Bent-core Liquid Crystals of Some Schiff Bases Containing Azo Linkage

The paper presents the synthesis and liquid crystalline properties of some new symmetric bentcore liquid crystals containing a 1,3-dihydroxybenzene central core disubstituted with mesogenic units consisting of three aromatic rings connected through esteric, azomethinic and azo groups. The wings are ended with terminal acyloxy or alkyloxy chains containing 6 to 10 carbon atoms. Compounds were obtained by the condensation reactions between some 4-((4-alcanoyloxyphenyl)azo)benzaldehydes or 4-((4alkyloxyphenyl)azo)benzaldehydes with the 1,3-phenylene bis(4-aminobenzoate) core. The new synthesized compounds were characterized from structural point of view (H NMR, C NMR, MS spectroscopy) and liquid crystalline properties (polarizing optical microscopy and differential scanning calorimetry). All the banana shaped compounds presented enantiotropic liquid crystalline properties, with a wideranging stability of mesophases both on heating and cooling cycles. The synthesized compounds presented a good thermal stability in the existence range of the mesophases as evidenced by thermogravimetric studies. (doi: 10.5562/cca2150)