Tough rubber composites with dynamic covalent bonds enhanced by multiscale reinforcement strategy

Vitrimer composites are composite networks with dynamic covalent bonds, opening new opportunities in scientific and industrial fields. However, vitrimer composites remain a conflict between dynamic performance and fracture resistance. Achieving both excellent dynamic performance and high fracture properties remains a formidable challenge, which limits their practical applications. Herein, we propose a multiscale reinforcement strategy to simultaneously enhance the dynamic performance and fracture properties of rubber composites by integrating dynamic covalent bonds and thiol-modified silica nanoparticles (denoted SH-silica; composites with χ wt% SH-silica are denoted SH χ%) into the rubber network. Dynamic covalent bonds along the polymer chains, at the matrix–silica dynamic interface, and between neighboring nanoparticles exhibit synergistic reinforcement across multiple length scales. The results show that the dynamic performance of the vitrimer composite reinforced with modified nanoparticles increased by 391 % compared with that of the composite with unmodified nanoparticles. Moreover, the intrinsic fracture toughness G c reached 1825 J m⁻ 2 (a 340 % increase over traditional rubber), while the fracture energy E f of notched specimens reached 1489 J m⁻ 2 (a 360 % increase over traditional rubber). This multiscale reinforcement can simultaneously enhance dynamic responsiveness, tensile properties and fracture resistance by adjusting the nanoparticle content, which is rarely achieved in traditional systems. The multiscale reinforcement strategy can be broadly applied to various rubber systems and establishes a design framework for developing the next generation of vitrimer composites.