Synthesis ofBifunctional Copolyesters via ChemoselectiveRing-Opening Copolymerization of δ‑Lactone Derived fromCO₂ and Butadiene with ε‑Caprolactone

3-Ethylidene-6-vinyltetrahydro-2<i>H</i>-pyran-2-one (EVP), derived from the telomerization of carbon dioxide (CO₂) with 1,3-butadiene, emerges as a promising intermediate for the production of high-value added materials from CO₂. However, the current impediment lies in the challenge of accessing selective ring-opening (co)polymerization of EVP because of unfavorable thermodynamics under mild conditions and the competitive polymerization of highly reactive CC double bonds. In this study, we report the chemoselective ring-opening copolymerization of EVP (selective ring-opening rather than vinyl polymerization) with ε-caprolactone (CL), even at room temperature, by using a phosphazene/urea binary catalyst. This process exclusively yields the ring-opening product of copolyester poly(CL-<i>co</i>-EVP). The resultant poly(CL-<i>co</i>-EVP)s exhibit predictable molar masses (<i>M</i>_ns), narrow distributions (<i>D̵</i> < 1.2 for most cases), wide range of EVP-contents (0–60 mol %), and thus tunable thermal properties. The kinetic and reactivity ratio (<i>r</i>_CL = 3.67 and <i>r</i>_EVP = 0.17) studies indicate a gradient structure for poly(CL-<i>co</i>-EVP). Moreover, these poly(CL-<i>co</i>-EVP)s possess two distinct pendant alkene groups, an internal one and a terminal one, which are ready to undergo sequential functionalization to prepare bifunctional polyesters or form cross-linked polyesters. Poly(CL-<i>co</i>-EVP) copolyester with only a 2 mol % EVP incorporation shows a significant improvement in both tensile strength (σ_b) and elongation at break (ε_b) in comparison to PCL homopolymer with a similar <i>M</i>_n, while cross-linking further facilitates the transformation of PCL from thermoplastics to elastomers. This study opens avenues to utilize EVP and synthesize sustainable and functional polyesters.