Synthesis and Properties of Diels–Alder‐Based Covalent Adaptable Networks from CO ₂ and 1,3‐Butadiene Derived Polyesters

ABSTRACT

α ‐Ethylidene‐ δ ‐vinyl‐ δ ‐valerolactone (EVL), a trifunctional monomer derived from CO ₂ and 1,3‐butadiene, provides a versatile platform for the construction of functional polyesters. A furan‐functionalized monomer (EVL‐FML), synthesized via thiol–Michael addition of EVL, exhibits a low ceiling temperature ( T _c = −102.4°C) that precludes its homopolymerization. To overcome this thermodynamic limitation, EVL‐FML is copolymerized with the Michael adduct of EVL and 1‐propanethiol (EVL‐SPr), which possesses a higher T _c of −2.4°C. Catalyzed by 1,5,7‐Triazabicyclo[4.4.0]dec‐5‐ene (TBD), the ring‐opening copolymerization (ROCP) yields polyesters bearing furan groups (PF‐x, 0–50 mol%) with number‐average molecular weights up to 13.1 kg mol ⁻¹ , and narrow distributions ( Ð  < 1.2). Kinetic studies reveal that the ROCP follows pseudo‐first‐order kinetics, with a reaction order of 0.37 with respect to TBD. The reactivity ratios are determined to be r _EVL‐SPr = 0.94 and r _EVL‐FML = 0.75. Subsequently, maleimide‐functionalized (13–59 mol%) polyesters (PM‐y) are prepared via post‐polymerization modification of PEVL‐SPr. Thermally reversible covalent adaptable networks (CANs) are constructed through the Diels–Alder reaction between PF‐x and PM‐y, exhibiting cross‐link densities ranging from 110 to 572 mol m ⁻³ and tensile strengths between 0.42 and 12.45 MPa. These networks demonstrate excellent self‐healing, reprocessability, and inherent degradability, offering a promising pathway toward sustainable functional materials.