CO2-Derived Dynamic Covalent Networks via Transesterification-mediated Backbone Functionalization

The linear "take-make-dispose" trajectory of conventional polymers causes continuous carbon leakage from fossil reservoirs to the atmosphere. To close this carbon loop, we propose a design strategy that combines a CO 2 -derived dynamic covalent network (DCN) with efficient physical recyclability. Two CO 2 -derived cyclic monomers, trimethylene carbonate (TMC) and EVP-Ph, a thiol–Michael adduct of 3-ethylidene-6-vinyltetrahydro-2H-pyran-2-one (EVP), are copolymerized to construct a vinyl-functional linear backbone precursor ( PTEV-ROP ). Mechanistic investigation reveals a transesterification-mediated chain-exchange process during the copolymerization, which inspires the development of a transesterification route that substantially improves EVP-Ph incorporation and molecular weight (MW), affording a high-MW linear precursor ( PTEV-TE , EVP-Ph conversion = 82%, M n = 8,600 g mol -1 ). The resulting precursor PTEV-TE is subsequently cross-linked through Diels-Alder (DA) chemistry to form thermally reversible DCNs, represented by PTEV-DA-3 with a total CO 2 mass content of 15%. The DCN exhibits excellent mechanical properties and can be repeatedly reprocessed via hot pressing, retaining over 90% of its toughness after three recycling cycles. By preserving the CO 2 -containing polymer framework during repeated processing and utilization, such a DCN design enables the circulation of fixed carbon throughout multiple life cycles.