A redox initiating system was developed in order to bypass 2,2‘-azobis(4-methoxy-2,4-dimethylvaleronitrile) (V70) as the initiator of the cobalt-mediated radical polymerization (CMRP) of vinyl acetate (VAc) in the presence of cobalt(II) acetylacetonate (Co(acac)2). It is indeed a problem to stock up with V70 because of needed storage at −20 °C during transportation. This paper reports on the controlled CMRP of VAc initiated by ascorbic acid combined with either lauroyl peroxide or benzoyl peroxide at 30 °C. Substitution of citric acid for ascorbic acid results in faster polymerization whereas the polymerization control is maintained. All these improvements facilitate the implementation of the vinyl acetate CMRP and open the door to the scale-up of the process.

Radical polymerization of styrene falls under control when conducted at 100 °C in the presence of an ortho-quinone, e.g., phenanthrenequinone (PhQ), and a catalytic amount of cobalt(II) acetylacetonate. Criteria for a controlled chain polymerization are fulfilled at least until 50% of monomer conversion, i.e., molar mass increasing with monomer conversion, molar mass predictable from the styrene/quinone molar ratio, linear time dependence of ln([M]0/[M]), and effective resumption of styrene polymerization by preformed oligopolystyrene. A tentative mechanism is proposed for this new system designated as quinone transfer radical polymerization (QTRP).