Ring-Opening Polymerization of a CO2-derived Tri-Substituted Six-Membered Lactone

The development of chemically recyclable polymers derived from CO2 is crucial for addressing carbon neutrality and polymer waste pollution. Among these, monomers derived from CO2 and 1,3-butadiene have shown promise due to their ability to form ester bonds and potential for monomer recycling. However, achieving controlled macromolecular topology and high molecular weight in these polymers remains challenging. This study introduces a novel trisubstituted six-membered lactone monomer, 3,3,6-triethyltetrahydro-2H-pyran-2-one (Et-HL), featuring gem-diethyl substitution that inhibits α-position initiated ROP for the first time. Using NaOMe and tBu-P4/BnOH catalysts, pure linear polymers were synthesized with molecular weights up to 31,829 g/mol-1 and dispersity as low as 1.05. Cyclic polymers were also produced using tBu-P4, achieving high molecular weights up to 1,050 kg/mol-1. Both polymer types demonstrated near-complete recyclability under catalytic conditions at 120°C. The study identifies distinct initiation mechanisms for Et-HL and HL monomers, contributing to an improved understanding of the ROP process. These findings offer another pathway for synthesizing CO2-based polymers with precise structural control and recyclability.