Supramolecular Oleogel-Impregnated Macroporous Polyimide for High Capacity of Oil Storage and Recyclable Smart Lubrication

Developing smart lubrication materials to achieve recyclable and durable lubrication and excellent wear resistance under various running conditions has great significance in fields ranging from aerospace to advanced engineering machinery but has proven challenging. Herein, a supramolecular oleogel with reversible gel-to-liquid transition was impregnated into macroporous polyimide (MPPI-gel) to obtain a smart lubrication material, which exhibited recyclable smart lubrication with an enhanced oil content and oil retention. The self-assembly of the gelator in polyalphaolefin10 (PAO10) formed three-dimensional networks that encapsulated the PAO10 during the service process, and the MPPI-gel could exhibit a high oil retention (approximately 99%). The gel-to-liquid transition allows the lubricant to be extruded and transferred to the surface of the macroporous matrix (MPPI) under thermal-mechano-stimuli and vice versa. The extruded lubricant can be sucked back into the MPPI pores through the capillary force and recovered to the oleogel when removing the external stimuli. Due to the high oil content, high oil retention, and recyclable lubricant releasing/reabsorbing, MPPI-gel exhibited recyclable smart lubrication (at least 1852 cycles; each cycle lasted for 1 h), a stable coefficient of friction (∼0.06) under alternating conditions (the frequency varied from 1 to 20 Hz, and the load varied from 10 to 46 N), and long-term conditions (at least 10 days). Therefore, MPPI-gel holds the promise of realizing smart lubrication according to the external stimuli with both high oil storage and recyclable lubricant releasing/reabsorbing with the porous matrix.