A Harsh-Environment Tolerant, Ultra-strong yet Tough Bio-Based Adhesive via General Branched-Topology Engineering: Break Adhesion-Toughness Conflicts

Abstract

Developing strong-yet-tough bio-based adhesives to replace conventional petrochemical-based ones is of great significance yet challenging, because of the inescapable trade-off between adhesion and toughness. Here, we introduce a general topology engineering strategy to develop a class of solvent-free bio-based epoxy adhesives (BSFA) integrating diverse harshenvironment adaptability, ultrahigh adhesion strength, and excellent toughness. Our method involves using rigid natural resveratrol as a branched topological node for crosslinking with flexible glyceryl ether. This design enables rational topology engineering via precisely tailoring the flexible chain length, which not only establishes a rigidity-flexibility balanced network rich in interaction sites but also attains favorable free-volume modulation to promote efficient energy dissipation, thereby optimizing both bulk and interface properties. Therefore, the optimal BSFA3 exhibits a tensile strength of 22.37 MPa alongside an elongation at break of 217.2% and a toughness of 23.27 MJ•m^-3 -an order-of-magnitude enhancement in both ductility and toughness compared to conventional epoxy adhesives, while preserving ultrahigh adhesion strength of 23.74MPa. This material also demonstrates excellent tolerance against ultralow temperature and various harsh wet (acid/base/solvent) environments, supporting multipurpose uses. Mechanistic studies reveal the crucial role of flexible chain length toward balanced adhesion and toughness. This approach can be expanded to other branched components for strongyet-tough adhesives.