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Polymer Bulletin, Vol.63, No.5, 623-635, 2009
Preparation of thermally stable and optically active organosoluble aromatic polyamides containing l-leucine amino acid under green conditions
An optically active bulky dicarboxylic acid (2S)-4-[(4-methyl-2-phthalimidylpentanoylamino)benzoylamino]isophthalic acid (1), was synthesized in five step starting from l-leucine and phthalic anhydride. A set of new aromatic polyamides containing (N-phthaloyl-l-leucine) units was synthesized by the direct one-pot phosphorylation polycondensation of diacid 1 with various aromatic diamines in the presence of different imidazolium salts and triphenyl phosphite (TPP) without adding extra compounds (Method I). This method was compared with a classical method in a medium consisting of TPP, N-methyl-2-pyrrolidinone, pyridine, and calcium chloride (Method II) and the results are comparable. The polymers were produced with high yields and from moderate to high inherent viscosities (0.43-0.81 dL g(-1)). Amino acid existence in this backbone results in optically active polymers. The chemical structures of some of these polymers were characterized by H-1-NMR and elemental analysis, and all of them with FT-IR and specific rotation tools. By introduction of bulky and flexible clusters in these new polyamides pendent group; make them soluble in most polar aprotic solvents.
Keywords:Polyamides;Ionic liquid;Amino acid;Optically active polymers;Thermal gravimetric analysis (TGA);Green chemistry