Multiscale dissipation enhances fatigue resistance of rubber nanocomposites with dynamic covalent bonds

Rubber nanocomposites are used in high-volume applications such as tires and dampers. Many of these applications require low fatigue damage to ensure structural durability and a high fatigue threshold to resist fatigue crack growth under cyclic deformation. However, particle reinforcements are known to increase the mechanical properties, but the fatigue damage is not suppressed, and the fatigue threshold remains difficult to improve. Traditional particle-reinforced composites are limited by the challenge between static mechanical properties, fatigue damage and fatigue threshold. To overcome this challenge, here, we propose an anti-fatigue strategy by integrating dynamic covalent bonds and thiol-modified nanoparticles into the rubber. The synergistic effect of dynamic covalent bonds within the matrix, at the matrix-particle interface and between particles enables energy dissipation across multiple scales. This multiscale dissipation not only suppresses fatigue damage, but also enhances the fatigue threshold and mechanical properties. We demonstrate that this rubber nanocomposite achieves a fatigue threshold of 727 J m^-2, representing a 341% increase over that of traditional materials, while also exhibiting enhanced mechanical properties. It shows a stress decay of only 6% and the damage resistance is improved by 42%. Our findings provide deep insights into the anti-fatigue designs for recyclable nanocomposites. This strategy offers a pathway for developing durable, sustainable, and high-strength composites and is expected to extend the life of existing structures.