Surface Modification of MoS₂ Nanosheets as Effective Lubricant Additives for Reducing Friction and Wear in Poly-α-olefin

Herein, MoS₂ nanosheets (MoS₂) densely modified with n-octadecyl mercaptan (NOM) are used as effective friction-reducing and antiwear additives. A facile and green strategy is employed to prepare the organic-inorganic hybrid nanosheets (MoS₂-NOM) by mussel-inspired chemistry combining with the Michael addition reaction. When MoS₂-NOM nanosheets are added in poly-α-olefin (PAO) 10, they form a homogeneous and stable dispersion compared to the unmodified MoS₂. Tribological measurements show that the dispersion of PAO 10 containing 1 wt % MoS₂-NOM displays dramatic reductions in the friction coefficient (∼53%) and wear volume (∼92%). The exceptional tribological behaviors of MoS₂-NOM are ascribed to the formation of a boundary protection film during tribochemical reactions. Further investigations display that the addition of 1 wt % MoS₂-NOM can efficiently improve the maximum load-carrying capacity and the high-temperature lubricating property of PAO 10 base oil, which is likely due to the formation of n-octadecyl thioether on the surface of MoS₂ after the modification of MoS₂-polydopamine (PDA) with NOM via Michael addition.