ABSTRACT
An alkylated fullerene which bears three eicosyl chains (3,4,5-C20C60, 1) was synthesized via [3 + 2] cycloaddition. At 25°C where the aliphatic chains are in the crystalline state, 1 exhibits a moderately improved solubility in paraffin oil compared to pristine C60. At 80°C which is well-above the chain melting temperature (Tc), a significant solubility increase was observed. Upon cooling to 25°C, suspension containing plate-like aggregates composed of lamellar subunits form, which can be stable for several days. Applications of 1 as a lubricant additive in paraffin oil (PO) for steel/steel contacts both below and above Tc have been investigated in detail. It was found that the addition of 1.0 wt% 1 to PO can reduce the friction coefficient by ∼24% at 25°C. Moderate reduction of the friction coefficient at 90°C was also observed. Analysis on the worn surfaces revealed a pronounced antiwear property of 1 by reducing the areas of the worn surfaces and smoothing the scuffing. Our results show that alkylated fullerenes can be potentially used as a new generation of lubricant additives. Finally, the lubrication mechanisms of 1 at different temperatures were discussed.
Acknowledgments
This work was financially supported by the Hundred Talents Program of Chinese Academy of Sciences (Y20245YBR1) and National Natural Science Foundation of China (no. 21402215, no. 61474124).