Journal
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
Volume 58, Issue 40, Pages 14311-14318Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/anie.201906140
Keywords
block copolymers; organometallic-mediated radical polymerization; poly(propylene carbonate); ring-opening copolymerization; switchable catalysis
Categories
Funding
- National Key RD Plan [2016YFB0302400]
- NSFC of China [21604027]
- CNRS (Centre National de la Recherche Scientifique)
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Switchable polymerization provides the opportunity to regulate polymer sequence and structure in a one-pot process from mixtures of monomers. Herein we report the use of O-2 as an external stimulus to switch the polymerization mechanism from the radical polymerization of vinyl monomers mediated by (Salen)Co-III-R [Salen=N,N '-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediamine; R=alkyl] to the ring-opening copolymerization (ROCOP) of CO2/epoxides. Critical to this process is unprecedented monooxygen insertion into the Co-C bond, as rationalized by DFT calculations, leading to the formation of (Salen)Co-III-O-R as an active species to initiate ROCOP. Diblock poly(vinyl acetate)-b-polycarbonate could be obtained by ROCOP of CO2/epoxides with preactivation of (Salen)Co end-capped poly(vinyl acetate). Furthermore, a poly(vinyl acetate)-b-poly(methyl acrylate)-b-polycarbonate triblock copolymer was successfully synthesized by a (Salen)cobalt-mediated sequential polymerization with an O-2-triggered switch in a one-pot process.
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