Ring-Opening Copolymerization of Lactide with Cyclic Ethers Using Different Catalytic Systems

There is a strong need to copolymerize lactide (LA) with other cyclic monomers to modify the physical properties of polylactide (PLA) materials and to introduce functional groups into the otherwise nonfunctional PLA chain. Among the readily available cyclic monomers, including commercial products, are cyclic ethers such as oxiranes, oxetanes, and oxolanes. However, achieving effective copolymerization of LA with these monomers requires carefully selected conditions and catalysts, which is not always straightforward. Over the past 25 years, numerous studies have reported LA copolymerization with cyclic ethers using a wide range of catalysts. This review is organized according to the size of the cyclic ether ring and the catalyst type, with particular emphasis on the most extensively studied 3-membered oxiranes. Copolymerization attempts with ethylene oxide and oxiranes bearing neutral or functional substituents are presented first, followed by examples involving substituted oxetanes and oxolanes. The concluding chapter provides a summary of these copolymerizations, including a personal comparison of the different catalyst groups applied to LA/cyclic ether systems. This review may serve as a useful resource for researchers aiming to synthesize PLA-based materials with targeted structures or modified properties, as well as for those seeking suitable catalytic systems for polymerization processes.