Synthesis and characterization of new heat-resistant polyamides bearing an s-triazine ring under green conditions

In this work, cyanuric chloride was reacted with morpholine to obtain 2,4-dichloro-6-morpholino-1,3,5-triazine, which was then reacted with 4-aminobenzoic acid, yielding a new triazine monomer containing dicarboxylic acid. The chemical structure and purity of this monomer was confirmed by different techniques. Direct polycondensations of this diacid with several aromatic diamines were carried out in a molten ionic liquid, tetrabutylammonium bromide. Polyamides (PAs) with moderate inherent viscosities in the range 0.32–0.38 dL g⁻¹ were obtained in high yields. These PAs were characterized by Fourier transform infrared spectroscopy, ¹H NMR spectroscopy, X-ray powder diffraction, inherent viscosity measurements, and elemental analysis. All of the PAs were found to be amorphous, to possess outstanding solubilities, and to be easily dissolved in amide-type polar aprotic solvents. The thermal properties of the PAs were evaluated by thermogravimetric analysis and differential scanning calorimetry. These polymers showed good thermal stability with glass transition temperatures (T _g) of 223–248°C, and their 10% weight loss temperatures were around 448°C and 460°C, confirming their good thermal stability. The char yields of these polymers were 53–59%, and, given their LOI values of 39–41, these polymers also show good flame retardancy.