Open Loop Recycling – Guanidine Iron(II) Polymerization Catalyst for the Depolymerization of Polylactide

Abstract

A previously reported non-toxic guanidine-iron catalyst active in the ring opening polymerization (ROP) of polylactide (PLA) under industrially relevant conditions was evaluated for its activity in the alcoholysis and aminolysis of PLA under mild conditions. Kinetic and thermodynamic parameters were determined for the methanolysis of PLA with [FeCl2(TMG5NMe2asme)] (C1) using 1H NMR spectroscopy. A comparison with the Zn analog of C1 showed that the metal center has a large impact on the activity for the alcoholysis. Further, the influence of different nucleophiles was tested broadening the scope of products from PLA waste. C1 is the first discrete metal catalyst reported to be active in the selective aminolysis of PLA. Catalyst recycling, scale-up experiments and solvent-free alcoholysis were conducted successfully strengthening the industrial relevance and highlighting aspects of green chemistry. Moreover, the selective depolymerization of PLA in polymer blends was successful. C1 is a promising catalyst for a circular (bio)plastics economy.