Fully atomistic molecular dynamics simulation of chemically modified natural rubber with hydrogen-bonding network

The incorporation of sacrificial hydrogen bonds is critical for the development of rubber materials with exceptional properties. However, the molecular-level mechanism by which sacrificial hydrogen bonds affect material properties is still poorly understood, significantly hindering the advancement of high-performance rubber materials. In this study, we employ fully atomistic molecular dynamics simulations to elucidate the impact of hydrogen bonds on structure, mechanical properties and linear viscoelasticity. Increasing the modified repeating unit ratio α leads to a rise in hydrogen bond content, particularly inter-chain hydrogen bonds, and the modified groups cluster due to hydrogen bonds. This hydrogen bond crosslinking network constrains the movement of the molecular chains, increasing the glass transition temperature. Surprisingly, the mechanical properties show an initial increase followed by a decrease as α increases, and the system with α=6% exhibits the optimal mechanical properties. This trend is due to the regulation of mechanical properties by the non-bond energy increment and bond orientation, with the system with α=6% exhibiting the maximum non-bonded energy increment and bond orientation. Increasing the self-healing temperature and time improves self-healing efficiency, essentially governed by the diffusion of molecular chains. The system with higher α exhibits a higher stress relaxation modulus and more extended stress relaxation plateau, attributable to a more complex hydrogen bond crosslinking network. Additionally, higher α values result in higher energy storage modulus, loss modulus, and complex viscosity but can effectively reduce the loss factor. Therefore, adjusting α can achieve a material with robust mechanical properties and low mechanical losses. Overall, we successfully establish the relationship between structure and properties and guide the designing and synthesizing of rubber materials with even better properties.