SARA ATRP or SET-LRP. End of controversy?

A debate has proceeded in the literature regarding the mechanism of reversible-deactivation radical polymerization in the presence of Cu 0. The two proposed models are supplemental activator and reducing agent atom transfer radical polymerization (SARA ATRP) and single electron transfer living radical polymerization (SET-LRP). In SARA ATRP, CuI is the major activator of alkyl halides, Cu0 is a supplemental activator and reducing agent of excess Cu II through comproportionation, and disproportionation is negligible. In contrast, in SET-LRP, Cu0 is the major activator, Cu I does not activate alkyl halides but instead undergoes instantaneous disproportionation. In this article we present a body of experimental and theoretical data, which supports the SARA ATRP mechanism and disagrees with the SET-LRP mechanism.