Triple Hybrid Polymeric Networks With Super‐High Adhesion at Ultralow Temperatures Enabled by Hierarchical Reinforcement Strategy

Strong and tough structural adhesives with durable adhesion and tolerance under ultralow‐temperature conditions are urgently needed for aerospace, polar exploration, and cryogenic engineering. Nevertheless, conventional adhesives rarely meet these demands. Herein, a novel strategy based on the construction of hierarchical reinforcement polymeric networks is proposed for developing strong and tough epoxy–siloxane–polyurea triple hybrid adhesives suitable for ultralow‐temperature environments. The strategy involves a reaction between dual‐reactive epoxy–oligosiloxane (EOSi) and amine‐terminated polyurea (APU) to form a highly crosslinked organic–inorganic hybrid network with residual reactive silanol groups and dense self‐compensating hydrogen bonds. Regulating the degree of condensation (DOC) of EOSi and the chain length of APU synergistically enhances the strength and toughness of the adhesives and achieves a balance between their cohesion and interfacial adhesion. The typical sample E 56 A 54 shows good mechanical properties (tensile strength of 28.2 MPa and toughness of 19.0 MJ·m −3 ) and adhesion properties. It also exhibits high adhesion strength to various substrates (up to 18.1 MPa on stainless steel). Notably, E 56 A 54 demonstrates durable adhesion performance after 30 days at ultralow temperatures (−196°C), achieving super‐high adhesion strength (30.5 MPa). This study provides a new effective strategy for developing strong and tough adhesives suitable for ultralow‐temperature environments.