α-Lipoate Functionalized Triblock Copolymers Enable In Situ Exfoliation of Molybdenum(IV) Disulfide into Nanosheets in Base Oils for Enhanced Friction and Wear Reduction

Although the nanosheet of molybdenum(IV) disulfide (MoS2) has been widely recognized as a high-performance green nanoadditive for friction reduction and wear resistance, its low isolated yield and poor colloidal stability in lubricating base oils have become bottlenecks for practical tribological applications. In this work, we report the synthesis of α-lipoate functionalized triblock copolymers and their utilization in directly dispersing bulky MoS2 as a form of oleogels. The resulting polymer-inorganic composite oleogels are characterized by microscopic imaging, small-angle X-ray scattering, and rheology, demonstrating that the bulky MoS2 is exfoliated in situ into nanosheets driven by multiple Mo-S coordinating bonds. Notably, this process does not require preexfoliation or separate synthesis of MoS2 nanosheets. The polymer-nanosheet networks exhibit long-term dispersible and colloidal stability in base oils and excellent lubricating properties. Furthermore, the degree of MoS2 exfoliation increases with the degree of polymerization of the α-lipoate-containing blocks, resulting in enhanced lubricating performance of composite oleogels. The improved lubricity is attributed to a thicker protective tribofilm enriched with MoS2 nanosheets formed on the rubbing surface. More importantly, the direct use of bulk MoS2 as a lubricant additive with the assistance of α-lipoate-containing triblock copolymers establishes a facile strategy for the design of highly efficient green lubricants.