Abstract
Living polymerizations involve the creation of polymer chains without significant irreversible chain transfer or chain termination1. Such processes are widely used to access well-defined macromolecular materials with controlled architectures, such as block and star polymers. Although this concept was first realized for anionic polymerizations in the 1950s2, many key recent advances have been made, most notably in the area of radical polymerization3,4,5,6. Here, we report a living photopolymerization that involves photoexcited monomers. Exposure of metal-containing ferrocenophane monomers to Pyrex-filtered light from a mercury lamp (λ>310 nm) or to bright sunlight in the presence of an anionic initiator leads to living polymerizations, in which the conversion and molecular weight of the resulting polymer can be controlled by the irradiation time. Photoirradiation selectively weakens the iron–cyclopentadienyl bond in the monomer, allowing the use of moderately basic and highly functional-group-tolerant initiators. The polymerization proceeds through attack of the initiator and propagating anion on the iron atom of the photoexcited monomer and, remarkably, the polymerization rate decreases with increasing temperature. Block copolymer formation is possible when the light source is alternately switched on and off in between sequential addition of different monomers, providing unprecedented, photocontrolled access to new types of functional polymers.
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Acknowledgements
N. Coombs and M. Mamak are acknowledged for their assistance with electron microscopy imaging. X. Lou is acknowledged for his help with the GPC experiments. G.W.M.V. thanks the Deutsche Forschungsgemeinschaft (DFG) for a postdoctoral research stipend. W.Y.C thanks the Natural Sciences and Engineering Research Council (NSERC) of Canada for a postgraduate scholarship. I.M. thanks the European Union for a Marie-Curie Chair and the Royal Society for a Wolfson Research Merit Award.
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Tanabe, M., Vandermeulen, G., Chan, W. et al. Photocontrolled living polymerizations. Nature Mater 5, 467–470 (2006). https://doi.org/10.1038/nmat1649
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DOI: https://doi.org/10.1038/nmat1649
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