In this study, a polymer gelator containing urea groups and dynamic disulfide bonds was prepared using the method of free radical aggregation. When added to base oil, it formed a tight and dynamic supramolecular network structure through the synergistic effect of dynamic covalent and non-covalent, exhibiting excellent mechanical adaptability while improving the heat resistance of lubricating oil. The tribological behavior of the prepared gel lubricants was comprehensively evaluated. The results revealed that the gel lubricants outperformed the base oil, exhibiting markedly lower friction coefficients (COFs), reduced wear rates, delivering exceptional extreme pressure resistance, and maintaining functionality in challenging and severe operating environments. Specifically, the gel lubricants delivered a 30% reduction in COF, 89% decrease in wear volume, and a maximum load-bearing capacity of 1500 N. Moreover, the gel lubricant enhanced the viscoelasticity of the base oil, promoting the formation of both an adsorbed film and a tribochemical protective film at the friction interface, which resulted in good tribological performance under fully lubricated conditions. The gel lubricant delivers exceptional tribological functionality while playing a pivotal role in eliminating environmental hazards caused by creep-induced oil leakage.

Perfluoropolyether (PFPE) oils pose challenges in terms of their compatibility with nanoparticle lubrication additives because of their unique molecular structure, limiting their lubrication performance enhancement. To address this issue, we propose the development of nanoparticle composite supramolecular gel lubricants, aiming to maintain the dispersion stability of molybdenum disulfide (MoS₂) nanoparticles within PFPE lubricants. This was achieved by harnessing the self-assembled three-dimensional (3D) network structure of supramolecular gels to entrap MoS₂ nanoparticles. The MoS₂ nanoparticles tended to cluster and settle in PFPE oils. However, the MoS₂-composite PFPE supramolecular gel lubricant (gel@MoS₂) exhibited exceptional dispersion stability over an extended period. MoS₂ nanoparticles used as additives in PFPE-based supramolecular gel lubricants not only enhanced the mechanical strength but also retained outstanding thixotropic properties. Additionally, nanoparticles improved the extreme pressure performance, anti-friction capabilities, and anti-wear properties of PFPE-based supramolecular gel lubricants under a high load of 300 N. Furthermore, the lubrication mechanism of the gel@MoS₂ composites was elucidated using focused ion beam-transmission electron microscopy and X-ray photoelectron spectroscopy. During the friction process, the 3D networks of the supramolecular gels, held together by weak interaction forces such as hydrogen bonds, halogen bonds, and van der Waals forces, were disrupted under continuous shear forces. Consequently, some of the MoS₂ nanoparticles and gelators migrated to the steel surface, forming a protective lubricating film. This research holds significant importance in prolonging the lifespan of equipment in critical sectors such as aerospace and aviation, where high-end lubrication is essential.

Supramolecular gelators can confine lubricating oils into gels and anchor them to the substrates, reducing friction and wear in mechanical engineering. However, excessive gel network confinement traps lubricants within gel clusters, hindering lubricant release, whereas the insufficient confinement is detrimental to a stable lubricating film formation in lubricant–gel–substrate anchoring system, both increasing friction and wear. Current strategies based on gelator polar groups design, simultaneously enhancing or weakening the confinement effect, are impractical for balancing this contradiction. To address this, we developed a carboxyl-based strong anchoring gelator and tailored the gel’s self-assembled network structure by adjusting alkyl chain effect, thereby effectively balancing the network confinement, inhibiting lubricant cluster formation, and reducing energy dissipation. Under friction, this design enables stronger lubricant anchoring at the substrate, forming a dual-confinement protective film that in-situ reduces the coefficient of friction (72%) and wear volume (94%). Compared with reported systems and commercial products, our gelator exhibited the highest friction-reducing and anti-wear performance. This research opens new perspectives in designing supramolecular lubricant confinement networks for achieving high-performance lubrication systems.

Developing functional additive resistant to space atomic oxygen (AO) irradiation through simple molecular design and chemical synthesis to enhance the lubricating performance of multialkylated cyclopentanes (MACs) oil is a significant challenge. Herein, sulfur-containing polyhedral oligomere silsesquioxane (POSS) were synthesize via a click-chemistry reaction of octavinyl polyhedral oligomeric with alkyl sulfide. The reduce-friction (RF), anti-wear (AW) properties and anti-AO irradiation of POSS-S-R as MACs base oil additives in atmospheric and simulated space environments were systematically investigated for the first time. Results demonstrate that POSS-S-R not only possesses outstanding anti-AO irradiation capacity but also effectively improves the RF and AW of MACs in atmospheric or simulated space surroundings. This improvement is due to the excellent anti-AO irradiation properties of the POSS structure itself and the high load-carrying ability of silicon-containing and sulfur-containing compounds generated by tribo-chemical reactions, which effectively separates the direct contact of the friction interface. We believe that this synthesized POSS-S-R is a promising additive for space lubricants.

The polyionic liquid poly-PEGMA-r-METAC (PPM) with quaternary ammonium has been synthesized and evaluated as additive in aqueous lubricating fluids. The rheological behavior of aqueous lubricating fluids with PPM has been characterized to confirm PPM’s function as a viscosity modifier. The tribological behavior of aqueous lubricating fluids with PPM has been investigated on SRV-V and MTM testing machines. It was found that PPM has excellent viscosity-increasing, lubricating, and anti-wear properties as an additive for aqueous, which can be attributed to the ability of PPM to form the protective film and boundary tribofilm generated from complex tribochemical reaction on rubbing surface. The obtained PPM with dual functions of anti-corrosion additives and viscosity index improver can play an important role in diverse lubrication regimes.

A new type of lubricating material (BTA-P₄₄₄₄-Lig) was synthesized by combining lignin with tetrabutylphosphorus and benzotriazole. The tribological properties, corrosion resistance, and anti-oxidation properties of BTA-P₄₄₄₄-Lig as a lubricant were investigated. The lubricating material exhibits excellent friction reduction and wear resistance, as well as good thermal stability and excellent oxidation resistance. Mechanistic analysis reveals that the active elements N and P in the lubricating material react with the metal substrate, and the reaction film effectively blocks direct contact between the friction pairs, affording excellent friction reduction and wear resistance. At the same time, the phenolic hydroxyl group in lignin reacts with oxygen free radicals to form a resonance-stable semi-quinone free radical, which interrupts the chain reaction and affords good anti-oxidant activity.

In this study, the direct intercalation of gemini ionic liquids (ILs) with different alkyl chains into the bentonite (BT) interlayer as a high-performance lubricating additive for base oil 500SN was investigated. The purpose of modifying BT with an IL is to improve the dispersion stability and lubricity of BT in lubricating oil. The dispersibility and tribological properties of IL–BT as oil-based additives for 500SN depend on the increase in interlamellar space in BT and improve as the chain length is increased. More importantly, the IL–BT nanomaterial outperforms individual BT in improving wear resistance, owing to its sheet layers were deformed and sprawled in furrows along the metal surface, thereby resulting in low surface adhesion. Because of its excellent lubrication performance, IL-modified BT is a potential candidate for the main component of drilling fluid. It can be used as a lubricating additive in oil drilling and oil well construction to reduce equipment damage and ensure the normal operation of equipments.

A series of new halogen-free dicationic ionic liquids (ILs) with different alkyl chain lengths were prepared, and the relationship between the alkyl chain length, physicochemical and tribological properties of ILs, and their role as neat lubricant for steel-steel friction pairs, was investigated. Evaluation of stability during hydrolysis and copper strip corrosion test results show that synthetic ILs are stable and not corrosive to metal contacts, due to the halogen-free anions. The friction and wear test results indicate that ILs with long alkyl chains have excellent friction-reducing and anti-wear properties, especially at high temperatures. Based on the surface three-dimensional (3D) profiles, electrical contact resistance, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and the X-ray photoelectron spectrometry (XPS) analysis of the worn surfaces of steel discs, we can conclude that the efficiency of ILs is due to the formation of high quality tribofilms that consist of both tribochemical reaction and ordered absorption films.

In this study, the gelling ability and lubrication performance of N-octadecyl-D-gluconamides (NOG) in liquid paraffin (LP), pentaerythritol oleate (PE-OA), and polyethylene glycol (PEG) oils were systemically investigated. The NOG, which could gelate the investigated oils, was successfully synthesized by a one-step method. The prepared gel lubricants were completely thermoreversible and exhibited improved thermal stability, according to the thermogravimetry analysis (TGA) reports. Rheological tests confirmed that the NOG gelator could effectively regulate the rheological behavior of the base oils. Tribological evaluation suggested that NOG, as an additive in the three types of base oils, could remarkably reduce the friction and wear in steel contacts. A plausible mechanism for the improved performances was proposed based on the mechanical strength of the gels and the formation of the boundary-lubricating film on the worn surface. The results indicated that NOG is a potential gelator for preparing gel lubricants with excellent tribological properties and environment-friendly characteristics.