Abstract
Abstract The intrinsic brittleness of bismaleimide (BMI) resins has long restricted their wider application in aerospace and automotive industries. Herein, a novel BMI-urea resin network that integrates flexible urea linkages into the rigid BMI matrix is developed. The obtained BMI-urea polymer combines elasticity with high strength. Molecular dynamics simulations and AI-assisted predictions revealed that Michael addition dominates over BMI self-polymerization, enabling rational design of hybrid networks. The nanoscale phase-separated morphology endowed BMI-urea with ductility and toughness while preserving strength and thermal stability. Fracture analysis revealed the enhancement of mechanical properties via rigid BMI segments providing reinforcement while flexible urea segments dissipating energy and suppressing crack propagation. The developed BMI-urea exhibited (i) tensile strength as high as 55 MPa, a 120% improvement over diamine-urea; (ii) impact strength as high as 208 kJ/m2, a 30% improvement over BMI; (iii) up to a 60-fold increase in elongation at break; and (iv) preserved thermal stability above 290 °C. Swelling resistance tests in three different media showed a dependence of solvent uptake on soft segment content and microphase separation. The current study introduces, for the first time, an elastic BMI-urea resin that combines toughness, strength, and thermal resistance, paving the way for advanced applications in aerospace composites and structural adhesives.