Ring-opening polymerization of γ-lactones and copolymerization with other cyclic monomers

Abstract Triggered by raised environmental awareness and the rising requirements for sustainable polymers such as degradable or recyclable polymers, studies on ring-opening (co)polymerization (ROP/ROCP) of (bio-based) cyclic monomers (e.g., cyclic esters, lactides, epoxides etc.) have been booming in recent years. Renewable five-membered γ-butyrolactone (γBL) and derivatives would thus be a desirable feedstock to produce poly(γ-butyrolactone) (PγBL) and different (bio-based) functional polyesters. Their copolymerization with other cyclic monomers could also afford an alternative to tune the properties of the resulting materials. Although γBL was traditionally regarded “non-polymerizable”, some progresses were made recently concerning the ROP/ROCP of γBL and derivatives. More importantly, some polyesters could be totally depolymerized back to their monomers by thermal or chemical treatment. This review is specially focused on ROP of γ-lactones and their copolymerization with other cyclic monomers by different catalytic/initiating systems, including Lewis/Bronsted acids, organic bases and alkali metal compounds, organometallic compounds, and cooperative bicomponent catalytic systems. The depolymerization process of some obtained polyesters is also discussed.