Toward Circular Polymer Materials and Manufacturing: Dynamic Bonding Strategies for Upcycling Thermoplastics and Thermosets.

The global production of plastics has reached unprecedented levels, with <10% being recycled and even fewer recycled more than once. This lack of circularity poses critical environmental threats. However, upcycling-recycling materials while improving their properties and functionality-through dynamic bonding strategies offers a promising approach to enhancing polymer sustainability. Dynamic bonds enable polymeric structures to reconfigure under specific conditions, improving thermal, chemical, and mechanical resilience and controllability while facilitating recyclability. This review specifically takes the viewpoint of upcycling existing thermoplastics and thermosets to develop sustainable dynamic covalent networks (DCNs). Integrating these DCN upcycling strategies into the design of additive manufacturing (AM) feedstocks creates unique benefits compared to traditional polymer systems. This approach is briefly highlighted in extrusion-based and light-based AM, assessing the potential for improved material processability, recyclability, and the creation of high-value customized products. The combination of upcycling technologies and AM techniques presents a significant opportunity to advance sustainability in macromolecular science.