Guanidine Carboxy Zinc Complexes for the Chemical Recycling of Renewable Polyesters

Abstract Our previously published non‐toxic guanidine carboxy Zn catalysts, suitable for lactide ring opening polymerisation (ROP) under industrially preferred melt conditions, have been tested towards the alcoholysis of renewable polyesters. A structure‐reactivity relationship has been found for the methanolysis of PLA in anhydrous THF, dependent on the substituents introduced at the ligand backbone. Using the unsubstituted “TMGasme” catalyst C2 , a polyester conversion of 41 % was reached after 5 h at 60 °C. Introducing an electron density donating ‐NMe 2 group at the ligand ( C3 ) caused and increase in catalyst activity, resulting in a PLA conversion of 72 %. Hence, C3 was further tested, stressing the industrial applicability of PLA chemical recycling. Catalyst recycling, process scale up as well as solvent free alcoholysis, with full degradation in the PLA melt after 1 h, were demonstrated, allowing for the implementation of a circular (bio)plastics economy promoted by these catalysts.