text: As the name suggests, the prerequisite of a successful RDRP is fast and reversible activation/deactivation of propagating chains. There are three types of RDRP; namely deactivation by catalyzed reversible coupling, deactivation by spontaneous reversible coupling and deactivation by degenerative transfer (DT). A mixture of different mechanisms is possible; e.g. a transition metal mediated RDRP could switch among ATRP, OMRP and DT mechanisms depending on the reaction conditions and reagents used.
  In any RDRP processes, the radicals can propagate with the rate coefficient k by addition of a few monomer units before the deactivation reaction occurs to regenerate the dormant species. Concurrently, two radicals may react with each other to form dead chains with the rate coefficient k. The rates of propagation and termination between two radicals are not influenced by the mechanism of deactivation or the catalyst used in the system. Thus it is possible to estimate how fast a RDRP can be conducted with preserved chain end functionality?
  In addition, other chain breaking reactions such as irreversible chain transfer/termination reactions of the propagating radicals with solvent, monomer, polymer, catalyst, additives, etc. would introduce additional loss of chain end functionality (CEF). The overall rate coefficient of chain breaking reactions besides the direct termination between two radicals is represented as k.
  In all RDRP methods, the theoretical number average molecular weight of obtained polymers, M, can be defined by following equation: 
  where M is the molecular weight of monomer; [M] and [M] are the monomer concentrations at time 0 and time t; [R-X] is the initial concentration of the initiator.
  Besides the designed molecular weight, a well controlled RDRP should give polymers with narrow molecular distributions, which can be quantified by M/M values, and well preserved chain end functionalities.
  A well controlled RDRP process requires: 1) the reversible deactivation process should be sufficiently fast; 2) the chain breaking reactions which cause the loss of chain end functionalities should be limited; 3) properly maintained radical concentration; 4) the initiator should have proper activity.