Microwave-assisted synthesis of optically active poly(amide–imide)s with benzophenone and l-alanine linkages

Rapid and highly efficient synthesis of poly(amide–imide)s was achieved under microwave irradiation by using a domestic microwave oven from the polycondensation reactions of 4,4′-carbonyl-bis(phthaloyl-l-alanine) diacid chloride [N,N′-(4,4′-carbonyldiphthaloyl)] bisalanine diacid chloride (1) with seven aromatic diamine (2a–2g) in the presence of a small amount of a nonpolar organic medium that acts as a primary microwave absorber. Suitable organic media was o-cresol. The polycondensation proceeded rapidly, compared with the conventional melt polycondensation and solution polycondensation and was almost completed within 10 min giving a series of poly(amide–imide)s with inherent viscosities about 0.36–0.85 dl g−1. The resulting poly(amide–imide)s were obtained in high yield and were optically active and thermally stable. All of the above compounds were fully characterized by means of FTIR spectroscopy, elemental analyses, inherent viscosity (ηinh), solubility test and specific rotation. Thermal properties of the poly(amide–imide)s were investigated using TGA/DTG.