Dynamic Polyimine Networks with Good Malleability and Closed-Loop Recyclability from Upcycled Poly(ethylene terephthalate) Waste

Abstract

Poly(ethylene terephthalate) (PET) waste is highly resistant to biodegradation and often downcycled. Although PET has achieved significant industrial success in closed-loop recycling via mechanical processes, these methods often face challenges such as property degradation and limited efficiency. Herein, we report an efficient strategy to upcycle PET waste into the reprocessable and close-loop recyclable polyimine (PIM) materials. Post-consumer PET bottles were depolymerized via catalyst-free aminolysis to bis(2-aminoethyl)terephthalamide (BAET), which was served as a key building block to construct PIM networks. The resulting networks feature dual crosslinking of dynamic imine bonds and amide-enabled hydrogen bonding, which synergically determine the thermal and mechanical properties of network. Due to the dynamic imine exchange, PIM networks exhibit the pronounced stress relaxation, heat and water-triggered shape reconfiguration, good self-welding and thermal reprocessing abilities. Furthermore, closed-loop recycling of PIM networks was achieved by two distinct pathways: (i) diamine-triggered dissolution into oligomer with direct repolymerization, and (ii) acid-catalyzed depolymerization to recover monomers. This work provides a powerful approach for the upcycling of PET waste.