Enhancement of the stimuli-responsiveness and photo-stability of dynamic diselenide bonds and diselenide-containing polymers by neighboring aromatic groups

The investigation of dynamic covalent bonds, which are exchangeable upon exposure to mild stimuli, represents an important topic toward the development of various advanced systems. Herein, we report enhanced dynamic properties for diselenide bonds that carry neighboring aromatic rings compared to their aliphatic derivatives. The bond exchange reactions in low-molecular-weight and linear polymer systems exhibit a faster equilibration for the aromatic diselenides relative to their aliphatic derivatives either under exposure to visible light or to heating (60 degrees C) in the dark. This behavior was rationalized in terms of i) the conjugated structures that contribute to the higher sensitivity toward longer-wavelength light, and ii) the homolytic dissociability via resonance stabilization of the dissociated radicals. Quantitative tensile measurements on cross-linked polyurethane in the bulk state revealed an improved healing capacity for those polymers that contain aromatic diselenide moieties relative to those that contain aliphatic diselenides. Furthermore, bulk cross-linked polymers and small molecules that contain aromatic diselenides exhibit higher photo-stability against UV light, demonstrating the potential of these bonds as stable and easy-to-handle dynamic covalent bonds.