Cationic ring-opening polymerization (CROP) major mechanistic phenomena

A number of today's accepted basic viewpoints related to cationic ring-open ing polymerizations (CROP) were a matter of vivid disagreements between var ious research groups in the past. These controversies are described in this article and reasons of some differencies in opinions are explained. It is shown in which way we learned that polyacetals are not exclusively cyclic ( as it was assumed), why CROP ions and ion pairs have similar reactivities, and why it was necessary to propose that CROP proceeds at certain condition s by Activated Monomer Mechanism. Among other subtle kinetic problems, appl ication of the dynamic NMR and "temperature jump" techniques in determining rate constants of active species interconversions are discussed. (C) 2000 John Wiley & Sons, Inc.