Alkyl-cyclens as effective sulfur- and phosphorus-free friction modifiers for boundary lubrication

Modern automotive engines will require new lubricant additives capable of handling higher power densities and temperatures. In this role, effective lubricant friction modifiers (FMs) must reduce friction and wear, while enhancing fuel efficiency and not poisoning catalytic converters. Here we report a new molecular FM design employing multidentate ring structures having multiple amine binding groups, each functionalized with a lubricious straight-chain hydrocarbon, to enhance FM surface adsorption strength and lubricant film durability in the critical boundary lubrication (BL) regime. As an example, a 1.0 wt% loading of the new thermally stable, sulfur- and phosphorus-free FM, 1,4,7,10-tetradodecyl-1,4,7,10-tetraazacyclo-dodecane, in a typical additive-free lubricating base oil exhibits strongly enhanced surface adsorption and friction reduction on steel surfaces versus commercially available non-cyclic FMs and a fully formulated commercial 5W30 motor oil. Specifically, at this wt% additive loading in the Group III base oil, the measured friction and wear are reduced by up to 70 % and 95 %, respectively, from the references established by using the base oil only in the BL regime over a wide temperature range.