The Mechanism and Thermodynamic Studies of CMRP: Different Control Mechanisms Demonstrated by Co-II(TMP), Co-II(salen*), and Co-II(acac)(2) Mediated Polymerization, and the Correlation of Reduction Potential, Equilibrium Constant, and Control Mechanism

摘要

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 degrees 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 x 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.