Rate of Redox Polymerization

The kinetics of redox-initiated polymerizations generally fall into two categories depending on the termination mode. Many of these polymerizations proceed in the same manner as other polymerizations in terms of the propagation and termination steps the only difference is the source of radicals for the initiation step. For these polymerizations where termination is by bimolecular reaction of propagating radicals, the initiation and polymerization rates will be given by appropriate expressions that are very similar to those developed previously  

Equations 3-40 and 3-41 differ from those (Eqs. 3-31 and 3-32) discussed previously in that the factor of 2 is absent from the expression for R, since typically only one radical is produced per oxidant-reductant pair. 

Some redox polymerizations involve a change in the termination step from the usual bimolecular reaction to monomolecular termination involving the reaction between the propagating radicals and a component of the redox system. This leads to kinetics that are appreciably different from those previously encountered. Thus, in the alcohol-Ce4+ system (Eq. 3-39), termination occurs according to 

By making the usual steady-state assumption (i.e., R, = Rt), one obtains the polymerization 

In many redox polymerizations, monomer may actually be involved in the initiation process. Although not indicated above, this is the case for initiations described under item 3b and, of course, for item 4. Rp will show a higher dependence on [M] in these cases than indicated by Eqs. 3-41 and 3-45. First-order dependence of Rt on [M] results in j- and 2-order dependencies of Rp on [M] for bimolecular and monomolecular terminations, respectively. 

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