Closed-Loop Recycling of Covalent Adaptable Network (CAN) Derived From Dopamine and Waste PET

Abstract

Covalent adaptable networks (CANs) have established a unique paradigm for developing recyclable thermosets. However, the majority of the CANs are derived from non-renewable resources. Incorporating bio-based feedstock in the design of CANs would further enhance sustainability. To this end, this work introduces a strategy to construct a CAN from bio-based dopamine and plastic (PET) waste. The pursuit of novel molecules for the derivation of CAN motivated us to introduce dopamine in this report. The dopamine was transformed into a tetra-functional alcohol monomer, which resulted in CAN upon polymerization with pyromellitic dianhydride. The CAN exhibited appreciable thermal stability, noteworthy mechanical properties, and excellent chemical and solvent resistance. The catalyst-free reprocessing of the CAN was demonstrated. The viscoelastic behavior of the CAN was examined using rheological measurements. Finally, toward achieving the closed-loop circular economy, the CAN was chemically degraded, and the monomer was recovered in high yield (91%) and purity, allowing the remaking of CAN. Our exploration expands the scope of diverse bio-derived feedstock toward the synthesis of CANs. To the best of our knowledge, this is the first report that describes the derivation of reprocessable thermoset-like CAN from dopamine and waste plastic and their subsequent chemical recycling.