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

Abstract

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.

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Acknowledgements

This work was supported by the 2018 Research Fund (1.180067.01) of the Ulsan National Institute of Science and Technology, and Basic Science Research Program through the National Research Foundation of Korea (NRF), which was funded by the Ministry of Education (NRF–2016R1D1A1B03936002) and National Honor Scientist Program (2010–0020414) of the NRF. The work at IMDEA was supported by the ‘Severo Ochoa’ programme for Centers of Excellence in Research and Development (MINECO; grant SEV–2016–0686), European Union structural funds and Comunidad de Madrid MAD2D-CM Program (S2013/MIT–3007), and Campus of International Excellence UAM + CSIC. Financial support at IMDEA and the University of Valencia was further provided by the Spanish Ministry for Science (MINECO–FEDER projects CTQ2014–58801 and CTQ2017–87054).

Author information

M.S.K. conceived and supervised the project. K.S.K. and J.G. supported and assisted in supervising the project. V.K.S. and M.S.K. designed the experiments and analysed the data. V.K.S. and C.Y. performed most of the experiments. S.B., Y.Kim, Y.Kwon, D.K., J.L., T.A. and G.T. helped with the synthesis of OPCs and polymerization studies. P.C.N., R.W. and L.L. performed advanced photophysical measurements. B.M.-M. and J.G. carried out the quantum chemical calculations. L.S.P. and J.L. advised on the experiments. V.K.S., K.S.K., J.G. and M.S.K. prepared the manuscript, with contributions from all authors.

Competing interests

The authors declare no competing interests.

Correspondence to Kwang S. Kim or Johannes Gierschner or Min Sang Kwon.

Supplementary Information

  1. Supplementary Information

    Supplementary Methods, Supplementary Notes 1–7, Supplementary Figures 1–86, Supplementary Tables 1–10 and Supplementary References

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Fig. 1: Strategy for OPC design.
Fig. 2: Molecular structures of OPCs.
Fig. 3: Analyses of the photophysical and electrochemical properties of OPCs.
Fig. 4: Photophysical and electrochemical properties of 2c.
Fig. 5: Photophysical and electrochemical properties of 4g.