Novel platinum‐containing initiators for ring‐opening polymerizations

A novel class of platinum‐based initiating systems for the ring‐opening polymerization of a wide variety of heterocyclic compounds including epoxides, oxetanes, and 1,3,5‐trioxane have been discovered. In addition to a platinum complex as a catalyst, a cocatalyst, consisting of a compound or polymer containing silicon‐hydrogen bonds must also be present. This article reports on a preliminary survey of the scope and limitations of these new initiator systems. Particular emphasis in this article has been placed on the ring‐opening polymerization of epoxides which have been studied in some detail and which proceed rapidly and exothermically at room temperature. A number of mechanistic studies have been conducted and the best current evidence suggests that polymerization proceeds by a cationic mechanism. Evidence is also presented which suggests that platinum metal colloids may function as the active initiating species.