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 anew 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 regio regular polycarbonates prepared by the organocatalyzed copolymerization of CO2-sourced exovinylene biscyclic carbonates(Bis alpha CC) with diols derived from biomass. These polymers ,thanks to their pending ketone groups, are rapidly (< 30 min) andtotally deconstructed into the parent diol and a bis(oxazolidinone)by catalyst-free aminolysis at 25 degrees C. By using 3-propanolamine forthe aminolysis, a hydroxy-functionalized bis(oxazolidinone) isrecovered, which can be copolymerized with Bis alpha CC 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 close-loop recycling scenario for this polymer. This work illustrates that these polycarbonates are prone to facile and complete aminolysisunder mild and catalyst-free conditions, but can also be exploited to prepare new building blocks for the synthesis of noveldegradable polymers. The mechanism of formation of these heterocycles is studied by model reactions and rationalized by densityfunctional theory (DFT) calculations.

Automated summary

This study presents a new type of degradable polymer that can be easily and completely degraded into its monomers under mild conditions through catalyst-free aminolysis. The recovered monomers can then be used for polymer synthesis, offering a closed-loop recycling scenario. This work is of great significance for addressing the accumulation of post-consumer plastic waste and providing building blocks for the synthesis of novel degradable polymers.