Controlled Cobalt-Mediated Free-Radical Co- and Terpolymerization of Carbon Monoxide.

While controlled free-radical polymerizations are established for a vast range of vinyl monomers, they have not been reported for carbon monoxide, although it is a unique monomer that forms in-chain keto groups which can promote, for example, desirable photo-degradability in polyethylenes. We report organometallic-mediated radical copolymerization of carbon monoxide with ethylene initiated by an organocobalt III compound to keto-modified polyethylenes with up to 15 mol % ketone repeat units. Terpolymerization with 2-methylene-1,3-dioxepane affords polyethylenes with in-chain ester and keto groups. Compared to ethylene homopolymerization, the controlled character of the copolymerization is strongly enhanced by the Lewis base function of carbon monoxide, which suppresses multiple unfavorable termination pathways.