Cobalt(II)-mediated catalytic chain transfer polymerization of styrene: Estimating individual rate coefficients via kinetic modeling

The individual rate coefficients for hydrogen abstraction (k_tr), cobalt-carbon bond formation (k_daec), and cobalt-carbon bond homolysis (k_ac) have been determined for the cobaloxime-mediated chain transfer polymerization of styrene at 60 °C using kinetic simulations in combination with experimental data. Values of 2.7 × 10⁶ L mol^-1 s^-1, 4.8 × 10⁴ L mol^-1 s^-1, and 8.7 × 10^-4 s^-1 for h_tr, k_deac, and k_ac, respectively, were found to adequately describe reactions associated with the catalytic chain transfer process with the overall model reproducing experimental observations such as molecular weight evolution with time and the initiator concentration dependency of the apparent chain transfer constant. The effect of photohomolysis of the Co-C bond, leading to an increased free catalyst concentration in the presence of strong UV radiation or a decreased free catalyst concentration under darkened conditions, was modeled by simply varying the value for k_ac.