Ring-opening metathesis polymerization of norbornene-based (macro)monomers is a powerful approach for the synthesis of macromolecules with diverse compositions and complex architectures. Nevertheless, a fundamental limitation of polymers prepared by this strategy is their lack of facile degradability, limiting their utility in a range of applications. Here we describe a class of readily available bifunctional silyl ether-based cyclic olefins that copolymerize efficiently with norbornene-based (macro)monomers to provide copolymers with backbone degradability under mildly acidic aqueous conditions and degradation rates that can be tuned over several orders of magnitude, depending on the silyl ether substituents. These monomers can be used to manipulate the in vivo biodistribution and clearance rate of polyethylene glycol-based bottlebrush polymers, as well as to synthesize linear, bottlebrush and brush-arm star copolymers with degradable segments. We expect that this work will enable preparation of degradable polymers by ROMP for biomedical applications, responsive self-assembly and improved sustainability.
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All data that support the findings of this study are available within the Article and its Supplementary Information, and/or from the corresponding author on reasonable request.
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The authors thank the National Institutes of Health (grant no. 1R01CA220468-01) for supporting this work. P.S. was supported by a fellowship from the American Cancer Society. H.V.-T.N was supported by the National Science Foundation (Graduate Research Fellowship).
P.S. and J.A.J. are named inventors on a patent application (US Patent application no. 16/542824) filed by the Massachusetts Institute of Technology on the monomers and copolymers described in this work.
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Shieh, P., Nguyen, H.V. & Johnson, J.A. Tailored silyl ether monomers enable backbone-degradable polynorbornene-based linear, bottlebrush and star copolymers through ROMP. Nat. Chem. (2019) doi:10.1038/s41557-019-0352-4