Preparation and Application of “Active‐Inert Chain Enveloping” Poly(Arylether Sulfone) Tougheners for Enhanced Compatibility With Epoxy Resin

ABSTRACT A novel active‐inert chain‐enveloping strategy was developed to enhance the toughness of epoxy resins by blending phenolphthalein‐based poly(arylether sulfone) (PPES) with carboxyl‐functionalized PPES (PPES‐C). The resulting composite toughening agent, PESP‐C, improves the properties of epoxy resins through chain entanglement and chemical crosslinking, forming a robust interfacial network. The flexible long‐chain segments of PPES‐C and the rigid PPES chains form a stable 3D network, enabling dynamic energy dissipation. Thermogravimetric and DSC analyses showed that T d5% > 370°C and T g = 135°C, indicating enhanced thermal stability and good compatibility. SEM confirmed the uniform dispersion of PESP‐C in the resin. With 10 wt% PESP‐C, the impact strength increased by 76.7%, reaching 23.5 kJ m −2 , and the fracture elongation increased by 81.0%, reaching 3.8, while the tensile strength remained high. Furthermore, free volume simulations and toughening mechanisms were studied, providing an optimized framework for efficient epoxy resin toughening.