High performance and multifunctional protein-based adhesive produced via phenol-amine chemistry and mineral reinforcement strategy inspired by arthropod cuticles

Arthropod cuticles are extraordinarily stiff and strong due to phenol-amine chemistry and mineral reinforcement. Nevertheless, these cuticles require costly dopamine (phenol provider), acid-unstable minerals, enzymes that can be deactivated, making them difficult to imitate in artificial materials. Herein, the arthropod cuticle was mimicked by introducing a low-cost phenolic polymer (DP) and acid-stable montmorillonite into an amino-rich soy protein matrix (SPI) to develop a bio-based adhesive. Fe3+ was chosen as the oxidizing agent to trigger the oxidation of DP without using enzyme, while activating cross-linking between oxidized DP and SPI to cure the adhesive. This covalent cross-linking and mineral reinforcement strategy endowed the adhesive with a bonding strength (1.04 MPa) comparable to industrial-use adhesives, whereas its volatile organic compounds emission was about 10-fold lower than the industrial-use adhesives. The sacrificial bonds and microphase-separated structure formed from the adhesive resulted in a high toughness. Furthermore, this adhesive featured an outstanding stiffness (40.38 GPa), exceeding ten times that of normal plastics. Notably, this adhesive exhibited excellent mold resistance (288 h shelf life) and flame retardancy (level B1 in GB 8624-2012). This efficient, ecofriendly, and low-cost bionic design strategy can advance the enhancement and functionalized modification of underwater adhesives, hydrogel, and composite materials.