From Molecular Design to Vacuum-Assisted Resin Transfer Molding: Homopolymerization-Inhibited Bismaleimides for High-Temperature Applications

The application of high-temperature bismaleimide resins in structural composites is inherently limited by the trade-off between thermal performance and processability. Here, we report a targeted molecular design strategy to overcome this operational bottleneck. By introducing bulky ortho-ethyl substituents into a monomeric architecture, premature homopolymerization was selectively suppressed up to 300 °C while maintaining the rigidity of the aromatic backbone. The resulting resin system provides an optimized processing profile for vacuum-assisted resin transfer molding (VARTM), characterized by low melt viscosity (<400 mPa·s) across a 120–140 °C range and isothermal stability exceeding 8 h. The fabricated carbon fiber reinforced polymer (CFRP) exhibits a high glass transition temperature (up to 277 °C) and retains 92.5% of its room-temperature flexural modulus at 250 °C (49 GPa). This strategy serves as a technological basis for the autoclave-free manufacturing of heat-resistant structural materials.