A one-pot approach towards polycarbonate-b-polyester block copolymers via chemoselective polymerization catalyzed by a one-component phosphonium borane Lewis pair

Chemoselective polymerization from mixtures of monomers to control the polymer sequence is a challenging task. In this contribution, we describe a unique chemoselective polymerization affording predictable (co)polymer compositions from a mixture of monomers. The use of a one-component phosphonium borane Lewis pair and a mixture of l-lactide (l-LA), cyclohexene oxide (CHO) and CO2 enables the selective synthesis of either a polyester, polycarbonate or poly(carbonate-b-ester). The selectivity depends on the nature of the borane–oxygen functionality at the growing polymer chain end, and can be controlled by the addition of CO2 as an exogeneous switch reagent.