Atom transfer radical polymerization activation rate constants

Transition metal-catalyzed atom transfer radical addition Atom transfer radical polymerization Equilibrium constant for atom transfer Activation rate constant for atom transfer Deactivation rate constant for atom transfer 2,2 -Bipyridine... 

Counterion, and Alkyl Bromides on the Activation Rate Constants in Atom Transfer Radical Polymerization. 36 599-604. 

In this mechanism, P-X is activated by the catalysis of activator A, and the capping agent is transferred to form a stable species AX. All currently known successful LRPs in this category use a halogen like Cl and Br as a capping agent X and a halide complex of transition metal like Cu" " and Ru as an activator A. These LRPs are commonly termed atom transfer radical polymerization (ATRP). The rate constants fea and feda defined in Scheme 3 are related to feact and fedeact by... 

Transition metal complexes functioning as redox catalysts are perhaps the most important components of an ATRP system. (It is, however, possible that some catalytic systems reported for ATRP may lead not only to formation of free radical polymer chains but also to ionic and/or coordination polymerization.) As mentioned previously, the transition metal center of the catalyst should undergo an electron transfer reaction coupled with halogen abstraction and accompanied by expansion of the coordination sphere. In addition, to induce a controlled polymerization process, the oxidized transition metal should rapidly deactivate the propagating polymer chains to form dormant species (Fig. 11.16). The ideal catalyst for ATRP should be highly selective for atom transfer, should not participate in other reactions, and should deactivate extremely fast with diffusion-controlled rate constants. Finther, it should have easily tunable activation rate constants to meet sped c requirements for ATRP monomers. For example, very active catalysts with equilibrium constants K > 10 for styrenes and acrylates are not suitable for methacrylates. 

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