Propagation rate constants, polymer tacticity

It can be seen from the data in Table I that there was no direct relationship between the syndiotactic triad content and the inductive or resonance effects of the substituents as indicated by their a constants, which is the parameter normally chosen for application of the Hammett equation to a reaction involving carbonium ion intermediates. A more detailed consideration of the theory for the relationship between polymer tacticity and propagation rate constants confirms that, in fact, no simple relationship should be expected. 

---