On the Absence of Gel Effect in Radical Ring-Opening Polymerization of Ketene Acetals

A new kinetic type of gel effect suppression in radical polymerization is described. Ring-opening polymerization of ketene acetals is characterized by auto-deceleration in the course of the reaction rather than the auto-acceleration, as well as increased reaction rate order with respect to the monomer. These features are caused by low reactivity of ketene acetals, as a result of which the addition of primary radicals to the monomer is the rate-limiting step in the initiation reaction. This should lead, firstly, to termination of the growth radicals at the primary radicals, and secondly, to the increased rate order with respect to the monomer concentration and, accordingly, to a decrease in the polymerization rate with its consumption.