UV–Vis Monitoring of Radical Polymerizations by Spin Trapping with Chromophoric Nitrones

The application of chromophoric radical spin traps for highly sensitive UV–vis monitoring of conversion of radical enhanced spin capturing polymerizations (ESCP) is presented. In ESCP the growing macroradical is reacting with a nitrone providing the corresponding polymeric nitroxide radical spin trap which will react irreversibly with a second macroradical to eventually give a polymeric alkoxyamine. The progress of styrene and n-butyl acrylate ESC polymerizations in the presence of π-conjugated nitrones is successfully visualized via a significant change of absorbance of the nitrone chromophore in the 200–500 nm range due to the nitrone transformation into an alkoxyamine moiety upon incorporation into the polymer. Moreover, related studies on UV–vis monitoring of photochemical rearrangement of nitrones to their corresponding oxaziridines are discussed.