A General and Mild Two-Step Strategy Using Bioderived Diols and CO2 for Chemically Recyclable Polycarbonates and Closed-Loop CO2 Fixation.

Developing chemically recyclable polymers using CO2 and sustainable co-feedstocks is an important strategy for achieving carbon-neutral production of new polymers and mitigating plastic pollution. Herein, a series of six-membered cyclic carbonate monomers with different alkyl α-substituents were synthesized using CO2 and bioderived 1,3-alkanediol as raw materials at room temperature and atmospheric pressure. The organocatalytic ring-opening polymerization was systematically studied using a range of common and readily available organocatalysts. Phosphazene base (t-BuP2) was identified as the most effective catalyst, offering excellent control over the entire polymerization. The regioselectivity of the synthesized polycarbonates, ranged from 0.74 to 0.99, with the highest value achieved when the side group was isopropyl (highest steric hindrance). Notably, the α-substituent in the mono-mers reduced the ring strains, allowing the resulting polycarbonates to be fully recycled to the monomers without decarboxylation. The recycling process effectively traps CO2 in a closed loop between monomers and polymers, preventing its release into the atmosphere. The alkyl side groups enhanced the hydrophobicity of the polycarbonates, thereby reducing the likelihood of CO2 release through hydrolysis during their lifecycle, achieving a robust CO2 closed-loop fixation. The utility of CO2-APCs as adhesives and the ability of copolymerization with L-lactide (L-LA) were explored.