Radical Polymerization of Methyl Methacrylate in the Presence of Cobaloximes and Benzoyl Peroxide

Abstract

The kinetics and inherent chain transfer on a monomer in radically polymerizing methyl methacrylate (MMA) by cobaloxime (LCo) catalysis in the presence of chemical substance of various types are described. Nonpolar solvents at content up to 40% v/v do not influence kinetics and molecular-weight distribution (MWD) of polyMMA. The addition of 1–5% v/v of polar solvents in MMA, e.g., DMF and other amides, DMSO and pyridine enhances the rate of reduction of LCo(III) (inactivated state of catalyst) to LCo(II) (active state of catalyst) by radicalas at initial stage of polymerization but does not change the rate of chain transfer catalysis (CTC). The reduction in bulk MMA and MMA containing polar solvents is proved to be an autocatalytic process. Starting rate constants of LCo(III) reduction ranged from 200 to 3000 m−1s−1 depending on the substitute at glyoximato ligands. Benzoyl peroxide and cumyl hydroperoxide were found to oxidize LCo(II) to LCo(III) in polymerizing MMA medium at a rate constant ca. 10 M−1s−1 and thus peroxides decline titled catalytic activity of cobaloximes by discovered rules providing a new way of CTC control. In the case of styrene (St) the benzoyl peroxide causes irreversible poisoning of cobaloximes.