Low‐molecular‐weight poly(imide‐amide)s obtained by copolycondensation of 4,4′methylenedi(phenyl isocyanate), trimellitic acid anhydride and benzoic acid in N‐methyl‐2‐pyrrolidone, 1. The microstructure studied by 1H and 13C NMR

Low‐molecular‐weight poly(imide‐amide)s (PIA) obtained by polycondensation at 180°C of 4,4′ ‐methylenedi(phenyl isocyanate), trimellitic acid anhydride and benzoic acid were studied by 1H and 13C NMR. Complementary 1H and 13C information was used to determine the distribution of II, IA, AA sequences and to show that the repartition of imide (I) and amide (A) groups along the chains is random. According to the composition of the monomer mixture, a slight deficiency of I is reproducibly observed. Non‐reacted benzoic acid is found, and unexpected traces of urea and amic acid groups are present in the PIA chains.