title: Alkyl-Cyclens as Effective Sulfur- and Phosphorus-Free Friction Modifiers for Boundary Lubrication.
abstract: Modern automotive engines operate at higher power densities than ever before, driving a need for new lubricant additives capable of reducing friction and wear further than ever before while not poisoning the catalytic converter. Reported in this paper is a new class of molecular friction modifier (FM), represented by 1,4,7,10-tetradodecyl-1,4,7,10-tetraazacyclododecane (1a), designed to employ thermally stable, sulfur- and phosphorus-free alkyl-substituted nitrogen heterocycles with multiple nitrogen centers per molecule. The multiple nitrogen centers enable cooperative binding to a surface which provides strong surface adsorption and lubricant film durability in the boundary lubrication (BL) regime. A 1 wt % loading of the cyclen FM 1a in Group III base oil exhibits strong surface adsorption, leading to excellent reductions in friction (70%) and wear (95%) versus the pure Group III oil across a wide temperature range. The lubricant with the new FM additive also outperforms two commercially available noncyclic amine-based FMs and a fully formulated commercial 5W30 motor oil.
authors.affiliation: Department of Chemistry, ‡Department of Mechanical Engineering, and ∥Department of Materials Science and Engineering, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.
authors.forename: Michael
authors.initials: M
authors.lastname: Desanker
authors.affiliation: Department of Chemistry, ‡Department of Mechanical Engineering, and ∥Department of Materials Science and Engineering, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.
authors.forename: Xingliang
authors.initials: X
authors.lastname: He
authors.affiliation: Department of Chemistry, ‡Department of Mechanical Engineering, and ∥Department of Materials Science and Engineering, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.
authors.forename: Jie
authors.initials: J
authors.lastname: Lu
authors.affiliation: Department of Chemistry, ‡Department of Mechanical Engineering, and ∥Department of Materials Science and Engineering, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.
authors.forename: Pinzhi
authors.initials: P
authors.lastname: Liu
authors.affiliation: Department of Chemistry, ‡Department of Mechanical Engineering, and ∥Department of Materials Science and Engineering, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.
authors.forename: David B
authors.initials: DB
authors.lastname: Pickens
authors.affiliation: Department of Chemistry, ‡Department of Mechanical Engineering, and ∥Department of Materials Science and Engineering, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.
authors.forename: Massimiliano
authors.identifier: http://orcid.org/0000-0002-4443-165X
authors.initials: M
authors.lastname: Delferro
authors.affiliation: Department of Chemistry, ‡Department of Mechanical Engineering, and ∥Department of Materials Science and Engineering, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.
authors.forename: Tobin J
authors.identifier: http://orcid.org/0000-0001-8771-0141
authors.initials: TJ
authors.lastname: Marks
authors.affiliation: Department of Chemistry, ‡Department of Mechanical Engineering, and ∥Department of Materials Science and Engineering, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.
authors.forename: Yip-Wah
authors.initials: YW
authors.lastname: Chung
authors.affiliation: Department of Chemistry, ‡Department of Mechanical Engineering, and ∥Department of Materials Science and Engineering, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.
authors.forename: Q Jane
authors.initials: QJ
authors.lastname: Wang
keywords: boundary lubrication; friction modifier; heterocyclic; lubrication additive; wear