Microwave-assisted rapid synthesis of novel optically active poly(amide-imide)s containing hydantoins and thiohydantoins in main chain

Rapid and highly efficient synthesis of novel optically active poly(amide-imide)s (PAIs) 6(a–f) was achieved using microwave irradiation. These were made from the polycondensation reactions of 4,4′-carbonyl-bis(phthaloyl-l-alanine) diacid chloride [N,N′-(4,4′-carbonyldiphthaloyl)] bisalanine diacid chloride 5 with six different derivatives of hydantoin and thiohydantoin compounds 4(a–f) in the presence of a small amount of a nonpolar organic medium that acts as a primary microwave absorber. Hydantoin and thiohydantoin derivatives 4(a–e) were synthesis from the reactions between benzil or benzil derivatives 3(a–e) with urea and thiourea. 5,5-Dimethylhydantoin 4f was synthesis from the reactions between acetone cyanohydrin 3f and ammonium carbonate. The polycondensation proceeded rapidly, and was completed within 10 min giving a series of PAIs with an inherent viscosity about 0.25–0.45 dL/g. The resulting PAIs 6(a–f) were obtained in a high yield and were optically active and thermally stable. All of the above compounds were fully characterized by means of Fourier transform infrared spectroscopy, elemental analyses, inherent viscosity (ηinh), solubility tests and specific rotation. Thermal properties of the PAIs 6(a–f) were investigated using thermal gravimetric analysis.