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‘B 2 type monomer, and 1,4-phenylenediamine, an A 2 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 AB 2 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 AB 2 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 1 H 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 60−61%. The terminal carboxylic acid groups were modified by reaction with a variety of aromatic amines to give the corresponding amide derivatives. The nature of the chain ends was shown to have a significant effect on the solubility and T g of the hyperbranched poly(amide−imide)s.