Phosphazene base-catalyzed living ring-opening polymerization system for substituted epoxides

Abstract

This comprehensive paper describes the anionic ring-opening polymerization of substituted epoxides using a phosphazene base catalyst, t-Bu-P4, and its application for the synthesis of architecturally complex polyethers. The t-Bu-P4-catalyzed ROP of 1,2-butylene oxide (BO) produced the poly(BO) having the predicted molecular weight and narrow polydispersity. The kinetic analysis revealed that the ROP system proceeded in a living manner. The t-Bu-P4-catalyzed ROP was then applied to the polymerization of various epoxides having a variety of side chains, e.g. styrene oxide. The synthesis of star-shaped polyethers was achieved by the t-Bu-P4-catalyzed ROP using polyols as an initiator. The syntheses of cyclic-, figure-eight-shaped, and tadpole-shaped polyethers were also achieved via the intramolecular click reaction of the well-defined linear precursors bearing azido and ethynyl functions at designed positions.