Biobased Recyclable Dynamically Cross-Linked Thermosets with Rapid Reprocessability via Guanidine Urea Linkages and Multiple Hydrogen Bonding

Conventional thermoset polyureas suffer from inherent limitations in sustainability and recyclability due to their irreversible cross-linked networks and heavy dependence on fossil-derived feedstocks. Herein, we report a biobased molecular design strategy for recyclable thermosets, leveraging guanidine acetic acid and lysine diisocyanate to construct a dynamic cross-linked architecture featuring reversible guanidine urea linkages reinforced by multiple hydrogen bonding interactions. This design endows the resulting material with both outstanding mechanical performance and rapid catalyst-free reprocessability. The synthesized poly(guanidine urea) thermoset exhibits a tensile strength of up to 37 ± 8 MPa and a glass transition temperature of 86 °C, rivaling that of commercial polyureas. Remarkably, the material can be reprocessed within 30 min under 120 °C and 10 MPa without a catalyst. This work offers a versatile molecular engineering approach toward the full life-cycle design of high-performance thermosets and paves the way for the development of recyclable, biobased polymeric materials, marking a significant step toward sustainable polymer innovation.