A comparative study of two different methods for direct polyamidation of N-trimellitylimido-L-methionine with various aromatic diamines

N-trimellitylimido-L-methionine (3) as optically active diacid monomer was prepared by the reaction of trimellitic anhydride (1) with L-methionine (2) in acetic acid solution at refluxing temperature. The direct polycondensation of this amide-imide diacid monomer 3 with several aromatic diamines was carried out with tosyl chloride (TsCl)/triphenylphosphine oxide (TPPO)/pyridine (Py) system (method I) and thionyl chloride (SOCl2)/Py system (method II) as condensing agents. For both methods I and II the optimized conditions for the reaction time, reaction temperature, aging time, amount of TPPO and TsCl were selected for polyamidation. The resulting novel poly(amide-imide)s (PAIs) were obtained in good yields. The inherent viscosities and thermal stability of the resulting PAIs from these methods were compared. The polymers obtained were fully characterized by IR, specific rotation, 1H-NMR spectra, elemental and thermogravimetric analyses.