Polyacrylic acid-based Low Transition Temperature Mixtures (LTTMs) for the exhaustive depolymerization of polyethylene terephthalate (PET)

The preparation and characterization of new solvents have garnered significant research interest in recent years, driven by the urgent need for biodegradable, sustainable, and high-performance solvents. Deep eutectic solvents (DESs) and low transition temperature mixtures (LTTMs) have emerged as promising strategies to meet these goals. For instance, recent studies have shown that iron-based DESs containing both Lewis and Brønsted acids can depolymerize polyethylene terephthalate (PET) under mild conditions. To the best of our knowledge, we report, here, for the first time, the preparation and characterization of a LTTM containing a high molecular weight Brønsted acid, namely polyacrylic acid (PAA), and FeCl3·6H2O as the Lewis acid. Although some limitations posed by the liquid features (water-sensitivity and corrosivity), detailed characterization was successfully conducted. Moreover, the mixture was proved to be active in the hydrolysis of PET, both in its pure form and when diluted with aqueous HCl, thus representing the first example where a polyacid-based LTTM is used for the effective depolymerization of PET.