Abstract
The mechanism study of cobalt mediated radical polymerization (CMRP) is performed with Co II (TMP), Co II (salen∗), and Co II (acac) 2 at 60 °C to demonstrate that the control of vinyl acetate radical polymerization is achieved via a degenerative transfer pathway when Co II (TMP) and Co II (salen∗) are used but via a reversible termination process with equilibrium constant (K eq ) equal to 1.4 × 10 6 m -1 when Co II (acac) 2 is the mediator. Given by the measured K eq in CMRP with varied cobalt complexes and the reduction potential (E 1/2 ) of the corresponding cobalt complexes, a linear correlation between log(K eq ), and E 1/2 is found and can be used to estimate the K eq of other CMRP systems. With the enriched database of K eq values, the control mechanisms of CMRP are quantitatively defined by Co II /Co III equilibrium constant. The connection of reduction potential, equilibrium constant, and control mechanism would contribute to the in-depth understanding of CMRP process. The control mechanisms in cobalt mediated radical polymerization (CMRP) are quantitatively defined by the Co II /Co III equilibrium constants, which are either measured by following the cobalt concentration or derived from the reduction potentials of corresponding cobalt species using the linear correlation of log(K eq ) and E 1/2 . The difference of control mechanisms in CMRP is demonstrated by vinyl acetate polymerization mediated by varied cobalt complexes as well.