Kinetics of Retarded Polymerization

In treating the kinetics of inhibited or retarded polymerization the usual kinetic scheme of initiation, propagation and termination can be used with an added inclusion of the transfer reaction between the chain radical and the inhibitor molecule Z 

For the sake of simplicity it will be assumed that the inhibitor radicals (Z ) do not initiate new polymer chains and also do not regenerate the original inhibitor molecule by reactions such as Eq. (6.165). 

In the presence of the inhibitor, the rate of radical termination will be given by 

The rate of strongly retarded polymerization is therefore dependent on the first power of the initiation rate iJj. This is in contrast to the polymerization in the absence of inhibitor or Oz 1 where the rate is dependent on iTj to a power one-half [Eq. (6.172)]. Mildly retarded polymerization falls in between these two limits. Equation (6.174) also shows that Rp is inversely dependent on the inhibitor concentration. 

Since inhibitor molecules combine with primary and chain radicals as and when they are formed, the inhibitor concentration decreases with time. If y is the number of radicals terminated per inhibitor molecule, the concentration of inhibitor, [Z], after a time t can be given by 

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