Improvement in the tribological properties of imidazolium‐derived ionic liquids by additive technology

Molecular design of wear-preventing and friction-reducing additives for ionic liquids is described. The tribological properties of carboxylic acid-derived additives were evaluated by a ball-on-flat type tribotest under reciprocating motion. Tetraalkylammonium and tetraalkylphosphonium salts of N-benzyl-protected aspartic acid were dissolved in 1-alkyl-3-methylimidazolium-derived ionic liquids. They prevented wear remarkably and reduced friction fairly. Influences of alkyl group in imidazolium molecule on additive response were observed. In tetraalkylammonium-derived ionic liquids, the additive reduced wear but did not reduce friction under these conditions. The salt of N-acetyl-protected glutamic acid prevented wear, but did not reduce friction. Copyright © 2008 John Wiley & Sons, Ltd.