Free radical polymerization disproportionation rate constant

In treatments of polymerization reactions that concentrated on a single feature, the effect of molecular weight upon the termination rate constant has been deduced, the relative rates of initiation of two monomers in a copolymerization have been assessed, constants for chain transfer to monomer have been obtained in an emulsion copolymerization, the relative amounts of chain termination by combination and disproportionation have been discovered from a molecular weight distribution, and the rate constant for long-chain branch formation in the free-radical polymerization of ethylene has been found by fitting a probalistic model. ... 

The carbon-centered radical stemming from the amine is able to initiate free-radical polymerizations of suitable monomers. a-Aminoradicals are especially suitable for the polymerization of acrylates [119] and are less efficient in styrene polymerization, which is explainable in terms of triplet quenching by styrene. In Table 9, rate constants for triplet quenching by various monomers are compiled. The ketyl radicals add due to resonance stabilization and, for steric reasons, only scarcely to olefinic double bonds but instead undergo recombination and disproportionation reactions, as shown in reaction (34). 

In this mechanism, P-X is thermally or photochemically dissociated into P and X", where a stable (persistent) radical X is assumed to be stable enough to undergo no reaction other than the combination with P" (and other alkyl radicals, if any present), namely, an ideal stable free radical (SFR) does not react among themselves, does not initiate polymerization, and does not undergo disproportionation with P". The best known examples of SFR are nitroxides such as TEMPO (2,2,6,6- tetra-methylpiperidinyl-l-oxy) (Figure 1), even though they are not perfectly ideal in the mentioned sense. The rate constants of... 

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