Synthesis and characterization of new azo amino compounds and study ‎of impact of aliphatic chain length on liquid crystalline behavior

Many novel mesogenic azo-Schiff base compounds have been produced successfully. An azo compound was obtained by a reaction of p-nitroaniline and hydrochloric acid with NaNO2 to prepare diazonium salt, this was followed by a coupling reaction with aniline to produce the final azo dye (II). While alkoxybenzaldehyde was prepared by reacting benzaldehyde with an alkyl halide (III). Finally, azo-Schiff bases were prepared by reacting azo dye with alkoxybenzaldehyde. The prepared compounds were diagnosed using FT-IR and 1H NMR spectrometers. A polarizing optical microscope (POM) and a differential scanning calorimeter (DSC) were used to study liquid crystalline properties. It was observed that the thermal stability of the liquid crystalline phases of the prepared compounds increased with the length of the aliphatic chain. In addition, most of the compounds gave liquid crystalline properties and more than one transition, and the reason for this is the molecular structure of the compounds. Likewise, increasing the length of the terminal groups decreased the melting points of the products.