Achiral bent-core azo compounds: effect of different types of linkage groups and their direction of linking on liquid crystalline properties

Abstract

We report, the design, synthesis and mesomorphic properties of six new homologous series of achiral bent-core compounds. In this study, we have investigated the effect of different types of linkage groups and their direction of linking, on the mesomorphic properties of azo functionalized compounds. The molecular structures of these newly synthesized compounds are characterized by spectroscopic methods. The liquid crystalline properties are studied using polarizing optical microscopy, differential scanning calorimetry, X-ray diffraction and electro-optical studies. We observed a variety of mesophases in these compounds, viz. N, B₁, B₂, SmA, SmA_dP_Aetc. From our investigations, we found that the type and the direction of the linkage group affects the thermal range or even sometimes the nature of the mesophase itself. We have also carried out photo-induced studies on the B₂ mesophase of some of the selected compounds and found that the reversal in the direction of linkage groups does affect the photochromic properties of the compounds.