Tunable tribological properties in water-based lubrication of water-soluble fullerene derivatives via varying terminal groups

In this paper, three kinds of water-soluble fullerene derivatives were synthesized via electrophilic addition reaction and cycloaddition reaction, respectively. The chemical composition characterizations of these derivatives indicated the successful preparation of C-60(OH) (x) , C-60(C(COOH)(2)) (x) and C-60(OH) (x) (NHCH2COOH)y fullerene derivatives. The aggregation and morphology characterizations showed that the three kinds of derivatives had an ideal spherical aggregating structures and excellent dispersibility in water, especially C-60(OH) (x) and C-60(C(COOH)(2)) (x) . The lubrication performance of the fullerene derivatives acted as lubricant additives were investigated at different concentrations in the range of 0-1 wt%. The results indicated that the addition of polyhydroxyl and carboxylic derivatives could improve the lubrication properties, which led to the reduction of wear to about 40% at most. It is attributed that the optimized substitutions of fullerene molecules may be of benefit to their distribution properties and lubricating behaviors in water based lubrication.