Electrochemically Controlled Copolymerization of Lactones for Block Polyesters

The electrochemical transformation of monomer mixtures into block copolymers remains a significant challenge. In this study, the ring-opening polymerization (ROP) and sequential copolymerization of lactones were developed using an electrochemical system with a Mg/Pt electrode. The electrochemical ROP of lactones, including L -lactide (LA), δ-valerolactone (VL), and ε-caprolactone (CL), was investigated in detail. It was demonstrated that the Mg anode undergoes an oxidation reaction to produce Mg 2+ ions that facilitate lactone activation and ring-opening. The electrochemical reduction process of lactone at the Pt cathode easily produces free radical anions for the ROP to produce polyesters. DFT calculations showed that the ring-opening of LA to form free radical anions presented a lower energy barrier than those of VL and CL. Thus, the controlled copolymerization of LA and VL, and of LA and CL were well performed for block polyesters in the electrochemical system. The structure of resulted PLA- b -PVL and PLA- b -PCL was characterized by FTIR, 1 H NMR, 13 C NMR, GPC, MALDI-TOF MS, XRD, and DOSY NMR. Moreover, an electrochemical system with a Pt/Pt electrode was developed for the degradation of prepared polyesters. This work provides that the electrochemical system was used for the facile preparation and degradation of polyesters.