Enzymatic recycling of polymacrolactones‡

The use of renewable monomers to make new polyesters which could replace the ones obtained from petrochemical resources employing green processes is attracting a lot of attention these days. With this in mind, three different macrolactones, ω-pentadecalactone, globalide and 6-hexadecenlactone, have been polymerized in bulk by enzymatic ring opening polymerization (e-ROP) using immobilized Candida antarctica lipase B to give their corresponding polymacrolactones (PMLs). For the first time, these PMLs have been depolymerized enzymatically in solution with the concourse of the same enzyme and at mild temperatures. GPC, NMR and ESI MS demonstrated that the main products recovered after the enzymatic processive recycling were cyclic monomers and dimers, with a small amount of higher size macrocyclic oligoesters (MCOs). It was observed that these depolymerizations followed a Michaelis–Menten kinetic model. Finally it was shown that these MCOs could be repolymerized. This research provides a biosynthetic method for chemical recycling of these interesting polymeric materials providing a pathway towards a circular economy.