High-Density Cleavable Epoxy Networks for Rapid Chemical Recycling to Monomer Recovery under Mild Conditions

Epoxy thermosets are widely used in advanced structural and electronic applications due to their excellent mechanical, thermal, and chemical stability derived from densely cross-linked polymer networks. However, the permanent network structure of conventional thermosets makes their recycling extremely challenging, often leading to downcycling or energy-intensive recovery processes. Here, we report a biobased epoxy thermoset derived from eugenol (Eu-EP) that incorporates a high density of multicleavable urethane bonds within both the epoxy monomer and curing agent. This molecular design enables rapid and uniform depolymerization of the cross-linked network under mild alkaline conditions (1 M NaOH, 50 °C) without the use of catalysts. Systematic depolymerization studies demonstrate efficient chemical recycling to monomers (CRM), achieving up to 94% recovery of key molecular components, including Eu-diol, eugenol, and curing agents. The recovered monomers were successfully reused to synthesize regenerated thermosets exhibiting thermal and mechanical properties comparable to those of the original materials. Furthermore, the depolymerization chemistry was extended to carbon fiber reinforced polymer (CFRP) composites, enabling selective matrix removal while preserving the woven architecture of the carbon fiber reinforcement. These results highlight the potential of multicleavable epoxy networks as a platform for chemically recyclable thermosets and sustainable composite materials.