Innovative PCL–PES-PCL Triblock Copolymer Optimized Epoxy Resin with Enhanced Interface Compatibility and Fracture Toughness

The inherent brittleness of epoxy resin (EP) caused by its highly cross-linked structure severely limits its application in advanced fields such as aerospace. Here, we innovatively synthesized PCL–PES-PCL (PCEC) triblock copolymer by grafting polycaprolactone (PCL) onto both ends of polyether sulfone (PES) to enhance the toughness of EP. The fracture toughness and impact strength of the PCEC/EP castings reached 3.16 MPa·m1/2 and 3.83 kJ/m2, respectively, representing improvements of 209.80 and 224.58% compared to pure EP, mainly contributed by the excellent compatibility between PCL block and EP increased debonding energy. The unique island and bicontinuous phase structures formed by PCEC prolonged crack propagation path and dissipated fracture energy. Furthermore, the flexural and tensile strengths of the EP remain unaffected even with adjustments in PCEC content. Our research highlights the promising potential of EP for applications in aerospace industries.