This work reveals the preponderance of an intramolecular metal chelation phenomenon in a controlled radical polymerization system involving the reversible trapping of the radical chains by a cobalt complex bis(acetylacetonato)cobalt(II). The cobalt-mediated radical polymerization (CMRP) of a series of N-vinyl amides was considered with the aim of studying the effect of the cobalt chelation by the amide moiety of the last monomer unit of the chain. The latter reinforces the cobalt-polymer bond in the order N-vinylpyrrolidone

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The Cobalt Mediated Radical Polymerization (CMRP) of vinyl 10 chloride (VC) in the presence of bis(acetylacetonato)cobalt(II) (Co(acac)2) as controlling agent is presented for the first time. Using an alkyl-Co(III) compound (R0-(CH2-CHOAc)<4-Co(acac)2; R0 = (H3C)2(OCH3)C-CH2-C(CH3)(CN)-) as an initiator, the bulk polymerization under non-isotherm conditions 15 is controlled. 1 H NMR spectra of the resulting PVC show that the CMRP process does not significantly affect the level of defects compared to a PVC prepared by a conventional free radical polymerization at the same temperature. Using the same alkyl-cobalt(III) compound, the copolymerization of VC and 20VAc is controlled at 40°C provided that enough VAc (about 40 mol%) is present in the polymerization medium to moderate the VC polymerization. In line with reactivity ratios, VC is preferentially incorporated in the polymer at the early stages of the polymerization, leading to copolymers with a high VC 25 content at moderate conversions. This is the first report of a CMRP of VC and of the synthesis of well-defined statistical PVC-co-PVAc copolymers by this technique.

Cobalt complexes supported on silica and Merrifield resin are effective mediators for the controlled radical polymerization of vinyl acetate.

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