¹⁵N NMR spectroscopy as a method for comparing the rates of imidization of several diamines

Abstract The relative rates of the conversion of amide‐acid to imide were measured for a series or aromatic diamines that have been identified as potential replacements for 4,4′‐methylene dianiline (MDA) in high‐temperature polyimides and polymer composites. These rates were compared with the ¹⁵N NMR resonances of the unreacted amines. The initial rates of imidization track with the difference in chemical shift between the amine nitrogens in MDA and those in the subject diamines. This comparison demonstrated that ¹⁵N NMR spectroscopy is appropriate for the rapid screening of candidate diamines to determine their reactivity relative to MDA, and can serve to provide guidance to the process of creating the time–temperature profiles used in processing these materials into polymer matrix composites. POLYM. COMPOS. 27:723–729, 2006. © 2006 Society of Plastics Engineers