Boundary Lubrication Mechanisms for High-Performance Friction Modifiers.

We recently reported a new molecular heterocyclic friction modifier (FM) that exhibits excellent friction and wear reduction in the boundary lubrication regime. This paper explores the mechanisms by which friction reduction occurs with heterocyclic alkyl-cyclen FM molecules. We find that these chelating molecules adsorb onto (oxidized) steel surfaces far more tenaciously than conventional FMs such as simple alkylamines. Molecular dynamics simulations argue that the surface coverage of our heterocyclic FM molecules remains close to 100% even at 200 °C. This thermal stability allows the FMs to firmly anchor to the surface, allowing the hydrocarbon chains of the molecules to interact and trap base oil lubricant molecules. This results in thicker boundary film thickness compared with conventional FMs, as shown by optical interferometry measurements.