Tailoring Densified Dual Networks via Synergistic Asynchronous Cross-Linking for High-Performance and Heat-Resistant Thermosetting Composites

Abstract

Despite excellent processability and mechanical properties, the inferior heat resistance of epoxy resins limits their advanced aerospace applications. To overcome the processing bottlenecks, phase separation, and structural-kinetic constraints inherent in conventional modifications, this study extends the thermomechanical limits of epoxies via a single-molecule heterofunctional design. Specifically, a low-viscosity monomer, 5-ethynyl-1,3-phenylene diglycidyl ether (E-Ph-DGE), was developed. Upon curing with 4,4’-diaminodiphenylmethane (DDM), the orchestration of reaction kinetics enables the synergistic asynchronous cross-linking of its functional units, constructing a continuous and densified dual network featuring bimodal nanomechanical domains. This unique topology significantly enhances both thermomechanical and interfacial properties. Compared to the commercial diglycidyl ether of bisphenol A (DGEBA) system, the E-Ph-DGE_DDM neat resin and its carbon fiber composite exhibit superior compressive strengths of 301.6 MPa (126% increase) and 1216 MPa (48% increase), respectively. The system achieves a glass transition temperature (Tg) of 293 °C, maintaining high creep resistance and interfacial adhesion to aluminum alloys (63% retention) and carbon fibers (75% retention) at 200 °C. Additionally, it demonstrates intrinsic low flammability. This strategy robustly resolves the processability-thermomechanical trade-off in thermosetting composites.