Sterically Hindered Oleogel‐Based Underwater Adhesive Enabled by Mesh‐Tailoring Strategy

Abstract Underwater adhesives hold significant relevance in daily life and numerous industrial applications. Despite considerable efforts, developing scalable, high‐performance underwater adhesives through a simple and effective method remains a formidable challenge. This study presents a novel mesh‐tailoring strategy for in situ, rapid, and ultrastrong oleogel‐based underwater adhesives (OUA), which comprises a highly crosslinked polyurethane network with a matching mesh size (≈2.22 nm) that precisely entraps bio‐based epoxidized soybean oil (ESO) molecules (≈2.31 nm) by steric hindrance effect. This oleogel exhibits unprecedented robust mechanical properties (≈35 MPa) and maintains stability under extreme conditions, including high temperatures (100 °C), high pressures (30 MPa), and immersion in various solvents (water, ethanol, or ESO). In particular, this oleogel displays high hydrophobicity, rapid curing, and strong interface affinity, resulting in ultrahigh underwater adhesion strength (up to 2.13 MPa) and exceptional substrate universality. Moreover, the remarkable environmental adaptability and stability of OUA enable its use in harsh aqueous environments, including acidic/alkaline, saline, and extreme temperature solutions. The comprehensive capabilities of the OUA underscore its potential for building underwater structures, repairing leaky containers, and sealing broken submarine pipelines. This research establishes the foundation for the designing of next‐generation underwater adhesives and offers fresh perspectives for exploring oleogel‐based materials.