Kinetics of Inhibition or Retardation

The kinetics of retarded or inhibited polymerization can be analyzed using a scheme consisting of the usual initiation (Eq. 3-14), propagation (Eq. 3-15), and termination (Eq. 3-16) reactions in addition to the inhibition reaction 

The steady-state assumption for the radical concentration leads to 

Equation 3-136 has been used to correlate rate data in inhibited polymerizations. A consideration of Eq. 3-136 shows that Rp is inversely proportional to the ratio kz/kp of the rate constants for inhibition and propagation. This ratio is often referred to as the inhibition constant z- 

It is further seen that Rp depends on Rt to a power between one-half and unity depending on the relative magnitudes of the first two terms in Eq. 3-136. Two limiting cases of Eq. 3-136 exist. When the second term is negligible compared to the first, the polymerization is not retarded, and Eq. 3-136 simplifies to Eq. 3-25. 

For the case where retardation is strong kz/kp 3 1), normal bimolecular termination is negligible. Under these conditions the first term in Eq. 3-136 is negligible and one has 

For the case where retardation is strong k /kp 1), normal himolecular termination is 

---

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... 

---