Synthesis and characterization of optically active and organosoluble poly(amide-imide)s containing imidazole rings as pendent groups by direct polycondensation

Abstract

Six new optically active poly(amide-imide)s (PAIs) 6a–f were prepared by direct polycondensation reaction of N-trimellitylimido-L-histidine 4 as a chiral diacid with various aromatic diamines 5a–f. Triphenyl phosphite (TPP)/pyridine (Py) in the presence of calcium chloride (CaCl2) and N-methyl-2-pyrrolidone (NMP) were successfully applied to direct polycondensation reaction. The resulting new polymers were in good yields, and had inherent viscosities ranging between 0.29 and 0.41 dL g−1 and were detected with elemental analysis, FTIR, 1H-NMR spectroscopy, specific rotation and differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), and derivative of thermaogravimetry (DTG). Imidazole pendent groups of the polymer chains disturb interchain and intrachain interactions and make these PAIs readily soluble in polar aprotic solvents such as N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), dimethylsulfoxide (DMSO), NMP and solvents such as sulfuric acid. Thermogravimetric analysis indicated that the residual weight percents of polymers at 600 °C were between 56.47% and 68.76%, which show their thermal stability.