A photoswitchable catalyst system for remote-controlled (co)polymerization in situ

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The fundamental properties of a polymeric material are ultimately governed by its structure, which mainly relies on monomer composition and connection, topology, chain length, and polydispersity. Thus far, these structural characteristics are typically set ex situ by the specific polymerization procedure, eventually limiting the future design space for the creation of more sophisticated polymers. Herein, we report on a single photoswitchable catalyst system, which enables in situ remote control over the ring-opening polymerization of l-lactide and further allows regulation of the incorporation of trimethylene carbonate and δ-valerolactone monomers in copolymerizations. By implementing a phenol moiety into a diarylethene-type structure, we exploit light-induced keto–enol tautomerism to switch the hydrogen-bonding-mediated monomer activation reversibly ON and OFF. This general and versatile principle allows for exquisite external modulation of ground-state catalysis of a living polymerization process in a closed system by ultraviolet and visible light and should thereby facilitate the generation of new polymer structures.

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Fig. 1: Photocontrol over l-lactide polymerization using diarylethene 1.
Fig. 2: Photoswitching performance of 1 and single-crystal X-ray structure of 1cK.
Fig. 3: In situ photoregulating the ROP of l-lactide using photoswitchable catalyst 1.
Fig. 4: Copolymerization experiments using photoswitchable catalyst 1 in a closed system.


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F.E. and M.K. are indebted to the Fonds der Chemischen Industrie and Studienstiftung des deutschen Volkes, respectively, for providing doctoral fellowships. Generous support from the European Research Council via ERC-2012-STG_308117 (Light4Function) is gratefully acknowledged.

Author information

F.E., M.K. and S.P.I. synthesized diarylethene 1. F.E. conducted ultraviolet visible spectroscopy and polymerization experiments, and analysed polymers via NMR and GPC measurements. F.E. and A.D. performed kinetics studies of polymerizations via NMR spectroscopy. T.S. conducted MALDI-MS measurements. B.M.S. solved the single-crystal X-ray structure. F.E., M.K. and S.H. conceived the idea, designed the study and wrote the manuscript. All authors discussed the results and edited the manuscript.

Correspondence to Stefan Hecht.

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Supplementary Methods, Supplementary Figures 1–48, Supplementary References

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Eisenreich, F., Kathan, M., Dallmann, A. et al. A photoswitchable catalyst system for remote-controlled (co)polymerization in situ. Nat Catal 1, 516–522 (2018) doi:10.1038/s41929-018-0091-8

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