A bio-inspired multifunctional soy protein-based material: From strong underwater adhesion to 3D printing.

• A multifunctional SPI-based underwater material (USPI-CaO) was developed. • USPI-CaO shows strong underwater adhesion and underwater bonding performance to substrates. • USPI-CaO can be used as underwater 3D printing material. • USPI-CaO shows antibacterial, mildew-resistant, and fire-resistant properties. • USPI-CaO has potential applications in various fields. The use of natural plant proteins to prepare underwater bonding materials with both strong adhesion and bonding performance underwater is a great challenge. Inspired by mussels and oysters, a Soy protein isolate (SPI)-based underwater adhesive (USPI-CaO) was designed and synthesized. First, 1, 2-epoxy-9-decene (A) was grafted onto SPI to obtain ASPI with unsaturated bond by ring-opening reaction. As a natural source of catechol groups, biological urushiol (U) was then grafted onto ASPI by free-radical polymerization to obtain USPI with underwater adhesion performance. Then, calcium oxide (CaO) was mixed with USPI to obtain inorganic-organic hybrid material (USPI-CaO) with underwater curing ability. The resultant USPI-CaO showed strong underwater adhesion and bonding performance to different materials (glass, metal, PVA, acrylic, wood, hogskin, rubber, ceramic etc., respectively) in different aqueous environments (pH = 5 or 9 water, simulated seawater, organic solvent, iron solution, T = 3 ℃ to 90 ℃ water, etc., respectively). Interestingly, USPI-CaO showed good plasticity and machinability in water, demonstrating its application prospects for underwater 3D printing and underwater fine machining. USPI-CaO also exhibited good antibacterial, mildew-resistant, and fire-resistant properties. USPI-CaO can potential be applied in various fields, such as sealing and repairing underwater/wastewater, wound and hemostatic dressings, wearable electronic devices, and submerged structures. [ABSTRACT FROM AUTHOR]