Hierarchical MoS2-Oleogel in Porous Polyimides: A Self-Adaptive Confined Lubrication Strategy for Ultralow Friction and Wear

Self-lubricating porous polyimides (PPI) are widely used in aerospace, microelectronics and other fields because of their excellent properties. The porous structure of PPI can present drawbacks, such as reduced surface strength, elastic collapse and diminished wear resistance, making the exploration of strategies to minimize surface wear of PPI essential for extending its service life and enhancing material stability. In this work, a novel self-lubricating porous polyimide (PPI-gel-TAM) with outstanding tribological properties is synthesized, exhibiting high oil-bearing capacity and superior retention stability. PPI-gel-TAM attains macro-superlubricity, exhibiting a coefficient of friction (COF) of ≈0.007. The wear rate of the PPI decreased significantly from 3.52 × 10 −5 to 2.81 × 10 −8 mm 3 ·N −1 ·m −1 after the incorporation of tannic acid-functionalized MoS 2 nanosheets (TA-MoS 2 ). The attainment of superlubricity is enabled by a self-adaptive confined lubrication strategy, which integrates the synergistic effects of four mechanisms: oil supply from the porous structure, the shear-thinning properties of lubricants, the interaction between functionalized MoS 2 and oil molecules, and the formation of a protective tribofilm. This study presents a novel and effective strategy for self-lubricating porous polymers to maintain both superior oil content and retention capabilities, while also exhibiting exceptional tribological properties.