Depolymerizing Polyethylene Terephthalate (PET) via “Imidazolysis” for Obtaining a Diverse Array of Intermediates from Plastic Waste

Abstract

Polyethylene terephthalate (PET) is a ubiquitous commodity plastic used in applications that include textiles, food packaging, drink bottles, and thermoplastic resins. Like other synthetic polymers, the massive accumulation of PET on Earth's surface has presented formidable environmental challenges. As a polyester, PET is susceptible to chain cleavage (i.e., depolymerization) via various "chemolysis" methods. Here, we introduce an approach to PET cleavage by imidazole (and related compounds): "imidazolysis". Reacting PET with excess imidazole yields 1,1′terephthaloylbisimidazole (TBI) which can be further transformed into an array of small products such as amides, benzimidazoles, and esters or potentially used as monomers for polymers. The TBI molecules obtained via imidazolysis are versatile intermediates (owed to their activated carbonyl groups), which can be stored and subsequently converted to specific final products later. This means that the target products do not have to be predetermined when the depolymerization reaction is carried out, and this methodology could provide flexibility to meet demands for various chemical products based on the terephthalic acid (or p-xylene) motif. Based on these results, imidazolysis may also be of broad utility in depolymerizing other polyesters, as well as polyurethanes (PUs).