Supramolecular gelator functionalized liquid metal nanodroplets as lubricant additive for friction reduction and anti-wear

Supramolecular gelator functionalized liquid metal (Gelator@GLM) exhibited excellent tribological properties due to the synergistic effect of GLM nanodroplets and the gel generating protective film. [Display omitted] •Supramolecular gelator functionalized liquid metal nanodroplets were prepared by self-assembly and radical polymerization.•The Gelator@GLM nanodroplets displayed effective anti-wear and friction reduction properties as lubricant additives.•The lubrication performance is attributed to the synergistic effect of GLM nanodroplets and the gel generating protective film. In this work, dopamine n-butenylamide (DBA) modified GLM nanodroplets were prepared via directional ultrasound of bulk liquid metal in ethanol aqueous solution as well as DBA self-assembly, followed by grafting with urea-based gelators via radical polymerization to obtain GLM-based supramolecular gelators (Gelator@GLM). The grafting gelators can impart their good compatibility between the GLM nanodroplets and the base oil, so that the Gelator@GLM nanodroplets can be dispersed in the base oil uniformly and stably for more than 3 weeks. Meanwhile, the tribological properties of Gelator@GLM nanodroplets was significantly enhanced, with a reduction of coefficient of friction (COF) and the wear volume of 41.18% and 92.13%, respectively, when compared with the base oil. Furthermore, Gelator@GLM additives exhibited stable lubrication performance even under variable temperature and frequency conditions. The synergistic effect of GLM nanodroplets and the gels generating a physical adsorption film and a chemically protective film (containing iron and chromium oxides, nitrides and carbides) can be credited with the improved tribological performance.