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.