Exploring frictional performance of diamond nanothread reinforced polymer composites from the atomistic simulation and density functional theory

Diamond nanothread (DNT), which has been recently found to outperform other conventional carbon-based nanomaterials, is a promising reinforcer for polymer composites. Here, we find that DNT can significantly improve the frictional resistance of polymethyl methacrylate (PMMA) composites via atomistic simulations and density functional theory (DFT) calculations. Results show that the friction coefficient of PMMA composite is reduced by 25.98% with the incorporation of DNT due to the excellent interfacial interactions including vdW interaction and mechanical interlocking. These lead to reduced cohesive energy at the Fe-PMMA interface and lower polymer mobility. The improvement of frictional resistance is more significant by nitrogen-doped DNT (by 43.72%) due to the rougher landscape of molecular electronic potential and larger binding energy, resulting in better interfacial interactions. Besides, it is found that the improvement of frictional resistance by DNT is less significant at elevated temperatures. The degrading mechanisms are attributed to the generation of free volume at the DNT-PMMA interface, which decreases the interfacial shear strength and weakens the interfacial interactions. These findings could make advances towards the understanding of physical mechanisms governing the frictional properties of polymer composites, and provides useful guidance for the design of advanced polymer composites with good service life.