Termination rate coefficient of dimethyl itaconate: comparison of modeling and experimental results

The termination kinetics of dimethyl itaconate (DMI) in bulk free radical polymerization at 40°C have been studied by both experimental and theoretical approaches. The chain length distributions obtained from pulsed laser polymerization experiments have been analyzed in combination with rate measurements to extract chain length dependent termination rate coefficients. The full chain length distributions were modeled using a comprehensive kinetic scheme with both experimentally determined and adjustable kinetic parameters. The chain length average termination rate coefficient, k_t, was found to be close to 5.5 × 10⁵ L mol^-1 s^-1. Termination occurs almost exclusively via disproportionation. Such low k_t values are typical for sterically hindered monomers. The chain length dependence associated with the termination rate coefficient is almost negligible. The reasons for the very weak chain length dependence may be due to the solvent quality of the monomer toward its own polymer or due to the rigid structure of the formed polymer chains, therefore preventing the formation of a statistical coil.