Catalyst-Free Approach for the Degradation of Bio- and CO₂-Sourced Polycarbonates: A Step toward a Circular Plastic Economy

Designing easily degradable polymers has become a new challenge to overcome the post-consumer plastic waste accumulation in the environment. Polycarbonates are important polymers that can be chemically recycled; however, most often, their degradation requires high temperatures and/or the use of catalysts. In this work, we report the facile chemical recycling of regioregular polycarbonates prepared by the organocatalyzed copolymerization of CO2-sourced exovinylene biscyclic carbonates (BisαCC) with diols derived from biomass. These polymers, thanks to their pending ketone groups, are rapidly (<30 min) and totally deconstructed into the parent diol and a bis(oxazolidinone) by catalyst-free aminolysis at 25 °C. By using 3-propanolamine for the aminolysis, a hydroxy-functionalized bis(oxazolidinone) is recovered, which can be copolymerized with BisαCC to yield a polymer alternating carbonate and oxazolidinone linkages. Importantly, the same bis(oxazolidinone) scaffold is recovered as the main product by aminolysis of this copolymer, offering a closeloop recycling scenario for this polymer. This work illustrates that these polycarbonates are prone to facile and complete aminolysis under mild and catalyst-free conditions, but can also be exploited to prepare new building blocks for the synthesis of novel degradable polymers. The mechanism of formation of these heterocycles is studied by model reactions and rationalized by density functional theory (DFT) calculations.