radicals (protected as closed-shell cobalt species). Systems based on degenerative transfer do not proceed via the persistent radical effect (PRE). Instead an active propagating radical interchanges its role with a latent radical in a dormant complex. The activation of one polymer chain means the deactivation of another polymer chain. If the exchange process is much faster than the polymerisation rate (kp), effectively all polymer chains grow at the same rate. Because the large polymer chains diffuse much slower than the small organic radicals, and thereby terminate much slower via 2nd order radical-radical coupling or disproportionation, long chains effectively build-up at cobalt while the small radicals keep terminating. This leads to a desirable narrow molecular weight distribution of the polymer at high polymerization rates. DT-CMRP is an associative process, which for CoIII(por)(alkyl) species implies formation of a 6-coordinate intermediate or transition state. Such Co(por)(alkyl)2 species formally have a Co(+IV) oxidation state, but in reality their (electronic) structure is best described as a weak radical adduct of a CoIII(por)(alkyl) species. A striking feature of DT-CMRP is the fact that even upon using a large excess of the radical initiator compared to the transfer agent, the radical polymerization reactions still remains controlled. A satisfactory explanation for this phenomenon seems to be lacking at the moment. See also Catalytic chain transfer Radical polymerization Living polymerization References Polymerization reactions