Thioketone-mediated polymerization of butyl acrylate: Controlling free-radical polymerization via a dormant radical species

It is demonstrated by experiment and simulation that the commercially available thioketone 4,4-bis(dimethylamino)thiobenzophenone is capable of controlling AIBN-initiated bulk butyl acrylate polymerization at 80°C. On the basis of molecular weight data and from monomer onversion versus time curves, the associated rate parameters are estimated. The addition rate coefficient, k_ad, for the reaction of a propagating chain with the thioketone is close to 10⁶ L · mol^-1 · s^-1 -1 and the fragmentation rate coefficient, k_frag, is around 10^-2 s^-1 giving rise to large equilibrium constants in the order of 10⁸ L · mol^-1. Furthermore, cross-and self-termination of the dormant radical species are identified to be operational.