Synthesis of well-defined cyclic polyesters via self-accelerating click reaction

Abstract

A metal-free and efficient homodifunctional bimolecular ring-closure method was developed specifically for the formation of well-defined cyclic polyesters based on the combination of ring opening polymerization (ROP) and self-accelerating double strain-promoted azide-alkyne cycloaddition (DSPAAC) reaction. In this method, ROP and the following end group modification were used to prepare the azide-terminated liner polyester precursors. The self-accelerating DSPAAC click reaction was then used to prepare the corresponding cyclic polyesters by ring-closing the linear polyester precursors with the small linkers of sym-dibenzo-1,5-cyclooctadiene-3,7-diyne (DBA). The distinct advantage of this novel homodifunctional bimolecular ring-closure method lied in the fact that the pure cyclic polyesters could be efficiently prepared by using excess molar amounts of DBA small linkers to ring-close the linear polyester precursors. This was resulted from the self-accelerating property of the DSPAAC ring-closing reaction.