Postmodification of Polymer Networks via the Freezing-Induced Generation of Radicals

We report polymer reactions triggered by freezing, in which pink radicals with yellow fluorescence, generated by the cleavage of the mechanophore tetraarylsuccinonitrile (TASN), act not only as reactive species but also as indicators of radical generation. The driving force of this reaction is the mechanical stress that TASN moieties in the cross-linkers of the polymer network experience due to solvent freezing; this stress leads to the homolytic cleavage of the TASN moieties to form carbon-centered radicals that react with the vinyl monomers. Electron paramagnetic resonance measurements revealed that the amount of radicals remains constant, providing a consistent reaction field.