Cobalt–Oxygen Bond Homolysis in the Bench‐Stable (Salen*)Cobalt(III) Acetate Complex: Insight into the Organometallic Mediated Radical Polymerization of Diverse Monomers
Résumé
Thermal activation of the [(Salen*)CoIII(OAc)] (Salen* = (R,R)-N, N'-bis (3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediamine) complex (1) allows to initiate the radical polymerization of methyl methacrylate (MMA) and methyl acrylate (MA) via CoIII─O bond homolysis. Catalytic chain-transfer has been identified as the dominant mechanism in the case of MMA, leading predominantly to α-H and ω-unsaturated polymeric chains, as deduced from MALDI-ToF mass spectrometry (MS). In contrast, the organometallic-mediated radical polymerization (OMRP) of MA is well-controlled, and the pseudo-livingness of the process could be highlighted by a linear increase of poly(methyl acrylate) (PMA) molar mass with the conversion, low dispersities, and the successful chain-extension of a CoIII-capped PMA macroinitiator with n-butyl acrylate (BA), leading to a well-defined poly(methyl acrylate)-block-poly(n-butyl acrylate) (PMA-b-PBA) block copolymer. MALDI-ToF MS and multinuclear NMR analyses allowed to identify two competing initiation processes for the OMRP of MA.
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