Developments in the theory of cationic polymerization

The polymerization of olefins by metal halides is discussed with special emphasis on the role of the co‐catalyst in these reactions. A new extension of the existing theory is proposed to account for some hitherto inexplicable observations, especially those relating to the effect of hydrogen halides on various polymerization systems. It is suggested that the carbonium ion which starts the polymerization may be formed by either of two essentially different reactions, depending on the nature of the catalyst, co‐catalyst and monomer. In one class of reactions the monomer reacts with a catalyst/co‐catalyst complex in the other the co‐catalyst reacts with a monomer/catalyst complex. In both cases a carbonium ion and a complex anion are formed.