Recent Developments and Optimization of Lipase-Catalyzed Lactone Formation and Ring-Opening Polymerization

To obtain materials useful for the biomedical field, toxic catalysts should be removed from the synthetic route of polymerization reactions and of their precursors. Lipase-catalyzed ring-opening polymerization and the synthesis of cyclic precursors can be performed with the same catalyst under different conditions. Here, we highlight the use of lipases as catalysts and optimization of their performance for both ring-closing and ring-opening polymerization, via varying parameters such as ring size, concentration, substrate molar ratio, temperature, and solvent. While the conditions for ring-closing reactions and ring-opening polymerizations of small molecules, such as ε-caprolactone, have been extensively explored using Candida antarctica lipase B (CALB), the optimization of macrocyclization, especially for more bulky substrates is surveyed here. Finally, recent methods and polymer architectures are summarized with an emphasis on new procedures for more sustainable chemistry, such as the use of ionic liquids as solvents and recycling of polyesters by enzymatic pathways.