Highly efficient organic photocatalysts discovered via a computer-aided-design strategy for visible-light-driven atom transfer radical polymerization

Organocatalysed photoredox-mediated atom transfer radical polymerization (O-ATRP) is a very promising polymerization method as it eliminates concerns associated with transition-metal contamination of polymer products. However, reducing the amount of catalyst and expanding the monomer scope remain major challenges in O-ATRP. Herein, we report a systematic computer-aided-design strategy to identify powerful visible-light photoredox catalysts for O-ATRP. One of our discovered organic photoredox catalysts controls the polymerization of methyl methacrylate at sub-ppm catalyst loadings (0.5 ppm-a very meaningful amount enabling the direct use of polymers without a catalyst removal process); that is, 100-1,000 times lower loadings than other organic photoredox catalysts reported so far. Another organic photoredox catalyst with supra-reducing power in an excited state and high redox stability facilitates the challenging polymerization of the non-acrylic monomer styrene, which is not successful using existing photoredox catalysts. This work provides access to diverse challenging organic/polymer syntheses and makes O-ATRP viable for many industrial and biomedical applications.