Ring-Opening Polymerization of CO₂-Based Disubstituted δ-Valerolactone toward Sustainable Functional Polyesters

3-Ethylidene-6-vinyltetrahydro-2H-pyran-2-one (EVL) is a disubstituent δ-lactone derived from CO₂ and 1,3-butadiene. In this contribution, we report the ring-opening polymerization (ROP) of EVL with β-butyrolactone (BBL) as the comonomer catalyzed by scandium triflate [Sc(OTf)₃]. The obtained polyester bearing active unsaturated bonds has the weight-average molecular weight (M_w) of 4.1 kg/mol, in which the EVL content is 38 mol % in accordance with the initial ratio of 40 mol %. The copolymers are characterized in detail and the cationic ROP mechanism has been confirmed by kinetic study, chain end analysis and density functional theory (DFT) calculation. The modification of the unsaturated bonds in EVL repeating units via the thio-ene click reaction with mercapto-ended polysarcosine polysarcosine yields the amphiphilic grafting polymers. It is a CO₂ fixation approach toward the functional poly(EVL-r-BBL) that is promising as a degradable polyester precursor for adhesive or surface-coating materials.