Synthesis of Hyperbranched Aromatic Poly(amide−imide): Copolymerization of B‘B2 Monomer with A2 Monomer

A hyperbranched aromatic poly(amide−imide) was prepared by the copolymerization of 4-(3,5-dicarboxyphenoxy)phthalic anhydride, a B‘B2 type monomer, and 1,4-phenylenediamine, an A2 type monomer. The rapid reaction between the anhydride and amino group led to the formation of the dominant imide intermediate which can be regarded as a new AB2 type of monomer. The intermediate, without isolation, was subjected to further polymerization in the presence of TPP/pyridine, as condensing agents, to give the hyperbranched poly(amide−imide), containing carboxylic acid chain ends. In comparison, the AB2 monomer was prepared separately, and the conventional self-polymerization of this monomer was also studied. The structures of the obtained polymers were characterized by FTIR and 1H NMR spectroscopy. The spectral data showed that these two polymers, prepared from two different synthetic approaches, have nearly identical structures. The degree of branching of the hyperbranched poly(amide−imide)s was estimated to be 60−6...