Preparation of biorenewable poly(γ-butyrolactone)-b-poly(L-lactide) diblock copolyesters via one-pot sequential metal-free ring-opening polymerization

The preparation of block copolymers containing poly(γ-butyrolactone) blocks remains a synthetic challenge owing to the unfavorable thermodynamics towards the ring-opening polymerization (ROP) of non-strained five-membered rings that makes them prone to copolymerization with other cyclic lactones or lactides rather than the formation of homopolymers. By choosing a suitable organophosphazene superbase as a catalyst, we realized the successful one-pot preparation of poly(γ-butyrolactone)-b-poly(L-lactide) by sequential ROP of γBL and L-LA for the first time. The thermal stabilities, crystallization, and melting behaviors of the obtained diblock copolyesters were also investigated.