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.