Highly improved mechanical and thermal properties of bismaleimide via a novel thermoplastic isoindolinone polyether sulfone

To improve the mechanical and thermal properties of thermosetting bismaleimide resins, a novel thermoplastic isoindolinone-based polyether sulfone (PES-In) resin was synthesized as a toughening agent for the N , N ′-(4,4′-methylenediphenyl)bismaleimide/2,2′-diallylbisphenol A (BDM/DABPA) system. The incorporation of this toughening agent not only enhanced the material's overall toughness but also significantly improved its thermal performance. The effects of PES-In's viscosity and dosage on toughening efficiency were systematically studied, leading to the identification of optimal conditions. Specifically, 7.5 phr PES-In with a viscosity of 0.4 dL/g resulted in a remarkable increase in the impact strength of the PES-In/BDM/DABPA system to 37.20 kJ/m 2 , representing a 497% improvement over the base BDM (6.23 kJ/m 2 ). Thermal properties, as assessed by dynamic thermomechanical analysis and thermogravimetric analysis, also showed significant enhancements, with T d5% and T g reaching 425 and 267°C, respectively, and the storage modulus rising from 2.0 to 2.5 GPa. Scanning electron microscope analysis revealed a typical “sea-island” toughening structure with multiple crack deflections on the impact fracture surface. The introduction of PES-In thus broadens the application potential of bismaleimide in higher-temperature-resistant structural materials. Highlights Novel isoindolinone-based polyether sulfone (PES-In) was synthesized. Toughness of bismaleimide networks by PES-In was significantly improved. Thermal performance of the PES-In/ BDM N /DABPA system was improved. Relative toughening mechanism was clearly elucidated.