Mechanism of free-radical degradation of poly(amidoimide) in the presence of nitrogen dioxide

The mechanism of free-radical transformations initiated in poly(amidoimide) by nitrogen dioxide was considered. As was shown by EPR spectroscopy, inte raction of nitrogen dioxide with amide groups of macromolecules results in the formation of iminoxyl and acylarylnitroxyl radicals. The iminoxyl radic als are the products of the reaction between nitrogen dioxide and the end g roups formed in the course of degradation of macrochains. The formation mec hanism of iminoxyl radicals was confirmed by the results of the study of th e reaction between nitrogen dioxide and n-quinone, which models the structu re of the end groups of poly(amidoimide) molecules, The degradation rate of the polymer was evaluated from the formation kinetics of iminoxyl radicals .