Ring-opening polymerization of cyclic esters mediated by base/(thio)urea binary catalysts toward sustainable polyesters

Aliphatic polyesters prepared by the ring-opening polymerization (ROP) of cyclic esters have shown great promise as sustainable polymers due to the potential bio-renewable feedstock, biodegradability and good material performance. The recently developed base/(thio)urea binary catalysts have achieved great success for the "living"/controlled ROP of cyclic esters due to their high catalytic activity and selectivity. In this review, we will highlight the latest achievements in the synthesis of sustainable polyesters mediated by base/(thio)urea binary catalysts. We first introduce the mechanistic insight of base/(thio)urea catalysts, focusing on the discussion of the impact factors on the catalytic mechanism, catalytic activity and selectivity. The ROP of a variety of cyclic esters, especially those with closed-loop recyclability, will be highlighted based on the ring size. Furthermore, the current limitations and future directions of base/(thio)urea catalysts will be discussed. The recent advancements in the synthesis of sustainable polyesters mediated by base/(thio)urea binary catalysts are discussed, focusing on the catalytic mechanism, activity and selectivity as well as the current challenges and future directions.