Enabling the Recyclability of Epoxy Networks via Dynamic Ether Linkages

Epoxy resins, which comprise a major portion of thermosetting polymers, are widely used across diverse applications due to their outstanding thermal and mechanical properties. Their limited recyclability, a major challenge arising from permanent covalent cross-linking, can be addressed by incorporating dynamic covalent linkages. Yet these linkages often compromise the thermal and chemical robustness of the material. Moreover, dynamic ether linkages, despite being the fundamental linkages in epoxy networks and imparting their robustness, have remained unexplored for the design of a recyclable epoxy network. Addressing these gaps, the present report introduces the design of recyclable epoxy thermosets by incorporating dynamic ether linkages, which endow the network with robustness while simultaneously imparting dynamic functionality and degradability. The epoxy networks were prepared via a solvent-free approach via melt transetherification of a difunctional benzyl ether-based epoxy with two different triols. The incorporation of robust ether linkages enabled excellent thermal stability and remarkable chemical and solvent resistance. Besides, a strategy to enhance the mechanical properties of the polymer was presented, wherein it was improved by further cross-linking and increasing the cross-link density. Varying the cross-link density, the polymer’s properties, including thermal stability, tensile strength, glass transition temperature, and dynamic behavior, were regulated. Transetherification-mediated bond exchange within the network enabled efficient reprocessability and viscous flow at elevated temperatures. Finally, in pursuit of a sustainable end-of-life solution, degradation and chemical recycling of the epoxy network were demonstrated. To the best of our knowledge, this is the first study that employs dynamic ether linkages for the design of robust and reprocessable epoxy networks and demonstrates their degradability. This study broadens the scope of designing a recyclable epoxy network.