Influence of ionic structure on tribological properties of poly(dimethylsiloxane-alkylene oxide) graft copolymers

Lubricants based on ionic liquid (IL) modified poly(dimethylsiloxane-alkylene oxide) graft co-polymers (GC) were synthesised by condensation of hydroxyalkyl groups linked to GC chains and to IL moieties. The tribological performances of neat and IL-modified co-polymers were investigated in reciprocating steel-steel and in rotating steel-PTFE contacts at 30 and 100 °C. A clear dependence of friction and wear on temperature was observed for both neat and IL-modified co-polymers. Generally, friction decreased at higher temperature, especially pronounced for neat co-polymers. Neat as well as IL-modified co-polymers tend to increase wear at elevated temperature. At 30 °C, the IL-modified co-polymers exhibited significantly improved anti-wear properties when compared to neat co-polymers with bis(trifluoromethylsulfonyl)amide anion being the crucial moiety involved in tribochemical reactions.