Synthesis and characterization of optically active poly(amide-imide)s with hydantoin and thiohydantoin derivatives in the main chain

Hydantoin and thiohydantoin derivatives 4(a-e) were synthesized from reactions of benzil and benzil derivatives 3(a-e) with urea and thiourea. 5,5-dimethylhydantoin M was synthesized from the reactions of acetone cyanohydrin 3f and ammonium carbonate. Benzil and benzil derivatives 3(a-e) were obtained from oxidation of benzoin and benzoin derivatives 2(a-e) with concentrated nitric acid. Benzoin and benzoin derivatives were obtained from benzoin condensation of benzaldehyde and benzaldehyde derivatives. Hydantoin and thiohydantoin derivatives 4(a-e) were characterized by melting points, elemental analysis, FTIR, H-1 NMR and C-13 NMR spectroscopy. The polyconclensation reactions of 4,4-carbonyl-bis(phthaloyl-L-alanine) diacid chloride 5 with six different derivatives of hydantoin and thiohydantoin compounds 4(a-f) were carried out in DMAc solution in the presence of pyridine. The resulting poly(amide-imide)s, PAIs, 6(a-f) with inherent viscosities about 0.15-0.38 dL/g 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 analysis, inherent viscosity (eta(inh)), solubility test and specific rotation. Thermal properties of the PAIs 6(a-f) were investigated using thermal gravimetric analysis (TGA).