Skin-Inspired Triple Dynamic Cross-Linking Design for High-Performance, Recyclable, and Photothermal Biobased Composites

A fundamental challenge in photothermal material design lies in the inherent difficulty of harmonizing mechanical properties, environmental friendliness, and strong photothermal response within a single system. Inspired by the skin's hierarchical, damage-responsive extracellular matrix (ECM), this study presents a fully biobased, recyclable, and photothermally active composite by designing a triple dynamic cross-linking network. The system integrates epoxidized natural rubber (ENR) as the matrix, plant-derived phytic acid (PA) as a green curing agent, and agricultural waste-derived biochar (BC) as a multifunctional filler. The designed network comprises: (1) phosphate ester bonds between PA and ENR, emulating collagenous scaffolds; (2) β-hydroxy ester linkages formed at the BC-ENR interface, providing stable interfacial anchoring; and (3) an extensive hydrogen-bonding network that dissipates energy in a way similar to the amorphous ECM matrix. This biomimetic multilevel design leads to outstanding mechanical properties, including a tensile strength of 11 MPa and an elongation at break of 509.7%, while retaining over 90% of the mechanical performance after reprocessing. In addition, the inherent photothermal capability of BC enables light-to-heat conversion, offering potential in energy-adaptive systems. This work presents a sustainable, ECM-inspired strategy for high-performance composites by integrating dynamic covalent and noncovalent bonds.