ortho-Aromatic Polyamides by Ring-opening Polymerization of N-carboxyanhydrides

We report the ring-opening polymerization of N-alkylated aromatic six-membered ring N-carboxyanhydrides (6-NCA-R) catalyzed by transition metal Schiff base complexes in the presence of a base. This system allows the facile synthesis of ortho-aromatic polyamides with high molecular weights via chain-growth polymerization. A mechanism is proposed based on the results of polymerizations performed under various reaction conditions. Copolymerization of 6-NCA-R with heterocyclic monomers is performed to prepare heteroatom (N, O, and S) containing copolymers. The thermal properties of the polymers with different N-alkyl side chains were investigated by thermogravimetric analysis, differential scanning calorimetry, and powder X-ray diffraction.