Facile Depolymerization of Thermally Stable Polyetherethersulfone and Polyetheretherketone Using Hydroquinone and Bases.

Super engineering plastics such as polyetheretherketone (PEEK) and polyetherethersulfone (PEES) exhibit thermal stability, chemical resistance, and mechanical strength. Such characteristics are attributed to their robust chemical structures composed of stable aryl ethers. These features make chemical recycling difficult. This is because it is necessary to overcome through the stability of the material and then precisely cleave the stable bonds. This study demonstrates the depolymerization of PEES and PEEK by hydroquinone in the presence of sodium hydroxide in 1,3-dimethyl-2-imidazolidinone (DMI) solvent at 150 °C. This method effectively provides monomeric products, diphenylsulfone and benzophenone having two 4-hydroxyphenoxy groups at both para positions. DMI solvent was the crucial factor for this transformation, since it enhanced the reactivity of hydroquinone to cleave the aryl ether bonds.