Preparation and Characterization of Low Degree of Branching Aromatic Polyamides from a New BB’B’’Triamine Monomer and Dicarboxylic Acids

Aromatic polyamides with multi amino end groups were prepared from a novel triamine (II) (BB’B’’) and dicarboxylic acids (A₂) in the presence of (2,3-dihydro-2-thioxo-3-benzoxazolyl) phosphonic acid diphenyl ester (DBOP) as a condensing agent. The corresponding polyamides were obtained in quantitative yields with inherent viscosities of 0.40–0.42 dL g^-1. The structure of the polyamides with low degree of branching was confirmed by nuclear magnetic resonance and by infrared spectroscopy. The amino terminal groups of the polymers were modified by reacting with acetyl chloride, benzoyl chloride and phthalic anhydride to give terminally modified polyamides. Although the degree of branching was as small as 0.05, their solubility in amide solvents was clearly improved. The end group modification of the polyamides greatly affected the thermal properties. Strong but brittle films were prepared by casting from N,N–dimethylformamide (DMF) solution. The mechanical properties were comparable with those of corresponding linear polymers.