Cobalt mediated radical polymerization (CMRP) has been recognized by the highly efficient control to radical polymerization of unconjugated monomers such as vinyl acetate (VAc) and was reported to be mediated by reversible termination (RT) and degenerative transfer (DT). These two mechanisms could be distinguished experimentally by the radical source and thermodynamically by the equilibrium constant of cobalt(II) and organo-cobalt(III) species. Since the core reaction in CMRP is the redox reaction between Co(II) and Co(III) complexes, the reduction potential (E1/2) was proposed to be correlated to the equilibrium constant (Keq), and thus control mechanism. A series of cobalt complexes have been used in CMRP of methyl acrylate as the mediators and a linear relationship between log(Keq) and E1/2 was established and could be used to estimate the Keq of CMRP using other complexes. With the enriched database of Keq values, the control mechanisms of CMRP were quantitatively defined by CoII/CoIII equilibrium constant. The connection of reduction potential, equilibrium constant, and control mechanism would contribute to the in-depth understanding of CMRP process.

Correlation of reduction potential, equilibrium constant, and control mechanism in cobalt mediated radical polymerization

254th National Meeting (2017)

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