Toughening epoxy resins: Recent advances in network architectures and rheological behavior

Epoxy resins are extensively employed in aerospace, electronic encapsulation, and high‐performance composites owing to their exceptional mechanical strength, chemical resistance, and interfacial adhesion. However, the high crosslink density of cured networks inherently imparts brittleness, limiting their service performance under impact loading and extreme environments. To achieve a synergistic enhancement of strength and toughness, recent efforts have focused on engineering multiscale toughening networks and leveraging rheological techniques to elucidate their structural evolution. In this review, we systematically examine epoxy resin toughening strategies by categorizing network architectures into heterogeneous systems (including rubbers, thermoplastics, core–shell polymers, and nanofillers) and homogeneous systems (hyperbranched polymers and bio-based materials), detailing their toughening mechanisms and fabrication approaches. We further discuss particle dispersion control methods and their influence on interfacial interactions and macroscopic mechanical behavior. Through both linear and nonlinear rheological characterization, we reveal the viscoelastic response and network development processes during curing. Synergistic toughening mechanisms such as interpenetrating dual networks and phase-separated morphologies are analyzed to highlight their intrinsic structure–property correlations. Finally, we identify current challenges in dispersion stability, sustainable synthesis, and structure–property modeling, and we outline prospective directions including multiscale in situ characterization and machine-learning-assisted formulation design. This comprehensive review aims to provide theoretical foundations and practical insights for the rational design and application of high-performance, eco-friendly, multifunctional epoxy resin systems.