Carbocationic alkene polymerizations initiated by organotransition metal complexes: An alternative, unusual role for soluble Ziegler-Natta catalysts

Several Ziegler-Natta (ZN) catalysts have been found to also induce carbocationic alkene polymerization. Further, it appears that ZN and carbocationic polymerizations may give materials with identical structures and end groups, and mechanistic differentiation of the two processes can be nontrivial. It is also possible that some carbocationic polymerizations have previously been incorrectly identified as ZN processes, or that polymers formed via ZN process may subsequently undergo carbocationic addition steps which could effectively shut-down ZN polymerization catalysis by the system. ZN catalysts-initiated carbocationic alkene polymerization is reviewed as an attempt to clarify the relationships between the two processes.