Construction of supramolecular oil gels via an acid–amide bicomponent gelator for enhanced mechanical lubrication

Abstract

An acid–amide bicomponent gelator, composed of 3,3′-dithiodipropionic acid and octadecylamine in a 1 : 2 molar ratio, was developed to construct supramolecular oil gels in base oils. The gelation mechanism involves the spontaneous self-assembly of gelator molecules into a well-defined 3D lamellar network, driven by van der Waals interactions and electrostatic forces. The representative poly(ethylene glycol) (PEG200) gel exhibited exceptional properties, including reversible heat and shear thixotropic behaviors, as well as high thermal stability, making it a promising candidate for semi-solid lubricants. Tribological evaluations revealed that the PEG200 gel (containing 6 wt% gelator) significantly outperformed the base oil, achieving remarkable reductions in friction (37.96–57.92%) and wear (43.71–59.06%) under demanding conditions such as high load, elevated temperature, and prolonged duration. Moreover, the addition of 6 wt% gelator enhanced the load-carrying capacity of neat base oil from 300 N to at least 600 N. The superior tribological performance of the PEG200 gel was attributed to the formation of a complex boundary lubrication film on the friction interface, consisting of a physical adsorption layer and a robust tribofilm. This dual-layer structure effectively minimizes the friction and wear, highlighting the potential of supramolecular gel lubricants for advanced mechanical lubrication applications.