A new class of supramolecular liquid crystals derived from azo calix[4]arene functionalized 1,3,4-thiadiazole derivatives

Abstract

A new class of bowl-shaped supramolecular liquid crystals (LCs) is described derived from calix[4]arene substituted with 1,3,4-thiadiazole derivatives, inbuilt with Schiff base and ester on the lower rim and with an azo group on the upper rim with an alkyl side chain (–OC₃H₇, –OC₈H₁₇). In the present investigation, we have synthesized six new supramolecular-based derivatives having three linking units with a substituted 1,3,4-thiadiazole ring and a variable trisubstituted side alkoxy chain on the lower rim of calix[4]arene. These supramolecular compounds were investigated by polarizing optical microscopy (POM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and high temperature X-ray diffraction studies (XRD). All synthesized compounds exhibited good blue fluorescence in solution under long wavelength UV light. The present compounds are promising for stabilizing the hexagonal columnar phase over a broad thermal range. The bowl-shaped calixarene-based LCs pack into columns with enhanced intermolecular interactions. The liquid crystalline properties are influenced by the structures of the spacers on the calix[4]arene skeleton and enhance the phase transition temperatures.