A strong, healable, recyclable bio-based adhesive via a bone-inspired triple network

Abstract

Conventional thermosetting adhesives are hindered by their irreversible cross-linked networks, presenting significant environmental challenges due to limited recyclability. Inspired by the hierarchical architecture of natural bone, a fully bio-based adhesive is realized through a biomimetic triple synergistic network, constructed from the cooperative reactions of epoxidized soybean oil (ESO), citric acid (CA), and tannic acid (TA). Irreversible ether linkages formed between ESO and TA establish a rigid scaffold analogous to the mineral phase in bone; dynamic β-hydroxy ester bonds generated from ESO and CA confer collagen-like reconfigurability; and the hydrogen-bonding network between TA and CA significantly enhances interfacial adhesion. The biomimetic triple network enables robust bonding performance, achieving a lap shear strength of 3.04 MPa on aluminum. Moreover, the reversible nature of β-hydroxy ester and hydrogen bonds not only confers excellent environmental resistance, efficient self-healing, and reusability to the adhesive, but also enables the cured network to be disintegrated in ethanol into a homogeneous dispersion and reprocessed, retaining the majority of its original adhesive strength after recycling. This work presents a high-performance, recyclable adhesive and establishes a bio-inspired design strategy for sustainable materials that balance mechanical robustness with circular functionality.