Synthesis and properties of novel brominated chiral polyamides derived from 5-[4-(2-tetrabromophthalimidylpropanoylamino) benzoylamino]isophthalic acid and aromatic diamines
A novel aromatic chiral dicarboxylic acid, 5-[4-(2-tetrabromophthalimidylpropanoylamino)benzoylamino]isophthalic acid was synthesized in three steps in high yield and purity starting from tetrabromophthalic anhydride and l-alanine. A series of new soluble, thermally stable and optically active polyamides (PA)s having pendent tetrabromophthalimide, flexible asymmetrical and benzamide groups with flame retardancy properties have been successfully prepared using triphenyl phosphite/pyridine in the presence of calcium chloride and N-methyl-2-pyrrolidone (NMP). The resulting new polymers were obtained in good yields, inherent viscosities ranging between 0.36 and 0.63 dL g−1 and were characterized with FT-IR, 1H NMR, specific rotation and thermogravimetric analysis techniques. Bulky pendent groups of the polymer chains disturb interchain and intrachain interactions and make these polymers readily soluble in various solvents, such as NMP, N,N-dimethylacetamide, dimethyl sulfoxide, and N,N-dimethylformamide. The resulting PAs were thermally stable, with 10 % weight loss recorded at 432 and 478 °C in the nitrogen atmosphere. In addition, due to existence of chiral center and optical activity of these polymers, they have potential to be utilized as chiral stationary phase in chromatography technique for the separation of racemic mixtures.