(36c) A New, Facile Approach to Epoxide Polymerization

A new class of initiator for the living polymerization of epoxides is presented, which are characterized as mono-µ-oxo-dialuminum (MOD) species. MOD initiators are synthesized in high yield in a single step using as-received commercial reagents with purification being accomplished by direct crystallization from the reaction medium. We studied the characteristics of the new initiators by the polymerization and copolymerization of various functional epoxide monomers such as allyl glycidyl ether, propargyl glycidyl ether, and epichlorohydrin. In-situ FTIR and NMR spectroscopy demonstrated that the polymerization was living, and produced materials with defined end-group and backbone functionality. Molecular weight of the resultant polymers could be precisely controlled (5–75 kg/mol) with relatively low dispersity (1.04–1.40). We also studied the effect of initiator structure and were able to yield a four-fold improvement in polymerization rate over traditional anionic polymerization, as well as gain mechanistic insight. From this, we propose a mechanism that accounts for the changes in polymerization rate with MOD structure. This new synthetic tool does not require special equipment, or an inordinate amount of synthetic skill in order to create new, functional polyether-based materials from inexpensive and readily available precursors.