Monitoring Free Radical Reactions in Degrading Polymers with a Profluorescent Nitroxide

摘要

The relative concentration and distribution of alkyl radicals in degrading polypropylene has been determined by competitive scavenging of the radicals with a profluorescent nitroxide: 1,1,3,3-tetramethyldibenzo[e,g]isoindolin-2-yloxyl; TMDBIO. On scavenging the alkyl radicals to form the alkoxy amine, the fluorescence of the phenanthrene chromophore in TMDBIO (previously suppressed by the nitroxide) is now observed. The nitroxide also stabilizes the polymer as shown by an oxidation retardation period. By comparing the chemiluminescence from the hydroperoxide reactions of the same sample, the retarding effect of the nitroxide may be quantified in terms of the kinetic chain length (or spreading coefficient) of the oxidation as well as the radical scavenging efficiency from the fluorescence.