Aspartic Acid-derived Wear-preventing and Friction-reducing Agents for Ionic Liquids

The first additives that improve the tribological properties of ionic liquids were designed. They were evaluated by a ball-on-flat type tribo-test under reciprocating motion. Tetraalkylammonium and tetraalkylphosphonium salts of N-protected aspartic acid was dissolved in l-alkyl-3-methylimidzolium bis(tri-fluoromethylsulfonyl)imide. They prevented wear remarkably and reduced friction considerably. The salt of N-protected glutamic acid prevented wear but did not reduce friction under the conditions we have evaluated. A new model of boundary film composed of liquid clathrate structure is proposed herein.