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

Abstract

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 ( η inh), solubility tests and specific rotation. Thermal properties of the PAIs 6( a–f) were investigated using thermal gravimetric analysis.