Biomimetic Octopus‐Like Graphene‐Based Toughener for Simultaneous Enhancement of Mechanical and Thermal Properties in Epoxy Composites

ABSTRACT Epoxy resins are widely used but often limited by brittleness and poor thermal stability. In this work, a novel octopus‐like toughener (FGO‐E51) was developed via a two‐step covalent grafting strategy. Bis‐isocyanate‐terminated HTBN was first grafted onto graphene oxide (GO) to form FGO, and its remaining isocyanate group was then reacted with hydroxyl groups of E51 epoxy resin, yielding FGO‐E51, a hybrid architecture designed to bridge GO and the epoxy matrix through covalent bonding. FTIR confirmed the sequential formation of urethane linkages, validating the molecular bridge structure. FGO‐E51 exhibited excellent dispersion and significantly enhanced thermal and mechanical properties. Compared to neat epoxy, the composite with 0.5 phr GO (EP‐4) showed a 23.6°C increase in glass transition temperature. Tensile strength, impact strength, and elongation at break increased by 25.1%, 144.4%, and 139.0%, respectively. Microstructural analysis revealed crack deflection and energy dissipation, indicating efficient toughening. This work demonstrates a rational design of reactive hybrid tougheners for high‐performance epoxy composites.