Covalent and ionic species in cationic polymerizations: Rates of exchange

Abstract The general kinetic scheme of simultaneous propagation on covalent and ionic species is discussed. There are a few ways of interconversion of covalent and ionic species, and at least two different modes of covalent propagation. This is either a direct inclusion with reformation of covalent species or reaction of covalent species with a monomer, giving ionic species, collapsing then into the covalent species and/or propagating ionically. Significance of these processes for the overall kinetics is discussed; rates of exchange covalent ⇌ ionic and covalent + monomer ⇌ ionic are discussed in more detail on the basis of trityl chloride ionization and ester‐ion equilibria in the polymerization of THF and oxepane.