Condensation polymers, such as poly(ethylene terephthalate) (PET), polyamides, polyurethanes, polycarbonate, polysulfone, and polyimide, comprise ~30% of the global plastic production. Although there has been progress on chemically upcycling condensation polymers, especially PET, most condensation polymers are not recycled because of the difficulty in depolymerization to pure building blocks in an energy-efficient manner. Catalysts are typically used to facilitate their deconstruction; however, catalytic deconstruction of condensation polymers has many challenges, including limited reactivity, yields, and control over product selectivity. Consequently, deconstruction of condensation polymers typically requires high temperatures that lead to the formation of small unselective fragments due to thermodynamically controlled processes. New processes and catalysts are needed to lower the energy requirements and temperature for the deconstruction of condensation polymers. Here, we have developed tailored ionic liquid organocatalysts synthesized by a simple and easy method to enable low-energy and greener depolymerization pathways for condensation polymers. For example, our catalyst enabled glycolysis with more than 95% conversion to pure monomer within 2 hours using 1/10 of the catalyst and minimum amount of ethylene glycol compared to the conventional organocatalysts. Besides its high efficiency and easy recyclability, the tailored ionic liquid organocatalyst also accomplished selective glycolysis of diverse mixed plastics. Our finding contributes to establish the design principles for energy-efficient polymer deconstruction and lay a versatile platform for polymer reconstruction with tailored composition, topology, and functionality.

Deconstruction and reconstruction of condensation polymers by tailored ionic liquids

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ACS Fall 2022

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