H-1 and C-13 NMR spectra of a hyperbranched aromatic polyamide from p-phenylenediamine and trimesic acid

The structure of hyperbranched aromatic polyamides synthesized from differe nt ratios of p-phenylenediamine and trimesic acid (A(2) + B-3 reagent pair) has been investigated by means of H-1 and C-13 NMR spectroscopy. On the ba sis of a detailed NMR signal assignment six 1,3,5-trisubstituted benzene mo ieties with different substitution patterns can be distinguished. The diffe rent monomer ratios influence the polymer architecture with respect to the content of these substructures, the degree of branching and the predominant functionalities (COOH or NH2). An excess of B-3 results in a larger number of branches and a predominant COOH functionalization. H-1 NMR proves site- specific interactions between lithium cations and the polymer substructures . The observed chemical shift effects simplify the quantification of the sp ectra. Finally, acetylation of amino groups by acetic acid, an impurity in commercial trimesic acid, could be proven.