Hyperbranched Topology-Modulated Epoxy Structural Adhesives with Superior Bonding Strength and Reliability in Harsh Environments

The increasing demand for structural adhesives in harsh environments has exposed the limitations of traditional epoxy resins, particularly their brittleness and poor environmental tolerance. Herein, a hyperbranched structure regulation strategy is proposed to develop epoxy resin adhesives with high strength and excellent environmental stability. Two triazine-based hyperbranched amine curing agents with different branching degrees, namely low-branched MA and highly branched MHBP6, were designed and synthesized, followed by cross-linking with glycerol triglycidyl ether (GTE) to construct cross-linked epoxy networks with distinct topological characteristics. The superior performance is attributed to the hyperbranched topology, which promotes the formation of a homogeneous cross-linked network and increases the accessibility of polar functional groups, thereby synergistically enhancing cohesive strength and interfacial interactions. The resulting epoxy resin (MHBP6-GTE45%) exhibits excellent mechanical performance, achieving a lap shear strength of up to 26.11 MPa on stainless steel substrates. Furthermore, the adhesive demonstrates remarkable durability, maintaining strength retention above 72% under acidic and alkaline environments (pH = 3–11), high humidity (75% RH for 30 days), seawater immersion, and ultralow temperature (−196 °C). Therefore, by regulating the hyperbranched architecture, this study provides an effective strategy for developing high-performance and highly stable adhesives.