Spider Silk-Inspired Adhesion–Cohesion Synergistic Enhancement Strategy: Competitive Hydrogen-Bonding-Induced Crystallization Phase Separation for High-Performance, Recyclable, and Multifunctional Biobased Adhesives

Although petroleum-based adhesives play an indispensable role in our daily lives, their widespread use has caused serious harm to humans and the environment. While biobased adhesives are ideal candidates for sustainability, they still suffer from weak adhesive strength. Thanks to the glycoprotein on its surface and its internal β-sheet nanocrystals’ phase-separated structure, spider silk possesses excellent adhesive and entangling properties. Here, inspired by the spider silk, an adhesion–cohesion synergistic enhancement strategy is proposed to achieve robust adhesive strength for biobased adhesives. Similar to spider silk, the phenolic hydroxyl endows the lipoic acid/tannic acid/carboxymethyl chitosan (LA/TA/CMCS) adhesive with excellent interfacial adhesion, while the competitive hydrogen bonding regulates the ratio of LA monomers in the adhesive to promote in situ formation of LA crystallization phase separation, which enhances cohesion. This biomimetic strategy yields a biobased LA/TA/CMCS adhesive with both strong adhesion and cohesion. The resulting adhesive demonstrates exceptional long-term adhesion (>150 days) across diverse substrates in dry (>7.2 MPa), underwater (>3.3 MPa), and under seawater (>2.6 MPa) conditions. Moreover, the adhesive offers full recyclability, environmental tolerance, and emergency long-term (>150 days) remediation capacity. This study pioneers a novel approach for designing high-performance, recyclable, and multifunctional green adhesives.