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

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 gamma-butyrolactone (gamma BL) and derivatives would thus be a desirable feedstock to produce poly(gamma-butyrolactone) (P gamma BL) 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 gamma BL was traditionally regarded non-polymerizable, some progresses were made recently concerning the ROP/ROCP of gamma BL 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 gamma-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. (C) 2020 Elsevier B.V. All rights reserved.