Dynamic Fluid‐Like Graphene with Ultralow Frictional Molecular Bearing

• Published in: Advanced materials (Weinheim) Vol. 31; no. 43; pp. e1903195 - n/a
• Main Authors: Jeon, Intak, Park, Gee Hoon, Wang, Pan, Li, Ju, Hunter, Ian W., Swager, Timothy M.
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.10.2019
• Subjects: Aerospace industry; Chemical properties; Coefficient of friction; coefficient of friction of 0.01; Diamonds; fluid‐like graphene; Graphene; Lubricity; Materials science; molecular bearings; Organic chemistry; Rigidity; Sliding; Stainless steels; Steel structures; Substrates; Thin films; triptycene; ultralow friction; Wetting; ultralow friction; triptycene; coefficient of friction of 0.01; fluid-like graphene; molecular bearings
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.201903195

Fluid‐like sliding graphenes but with solid‐like out‐of‐plane compressive rigidity offer unique opportunities for achieving unusual physical and chemical properties for next‐generation interfacial technologies. Of particular interest in the present study are graphenes with specific chemical functionalization that can predictably promote adhesion and wetting to substrate and ultralow frictional sliding structures. Lubricity between stainless steel (SS) and diamond‐like carbon (DLC) is experimentally demonstrated with densely functionalized graphenes displaying dynamic intersheet bonds that mechanically transform into stable tribolayers. The macroscopic lubricity evolves through the formation of a thin film of an interconnected graphene matrix that provides a coefficient of friction (COF) of 0.01. Mechanical sliding generates complex folded graphene structures wherein equilibrated covalent chemical linkages impart rigidity and stability to the films examined in macroscopic friction tests. This new approach to frictional reduction has broad implications for manufacturing, transportation, and aerospace. Fluid‐like graphene shows macroscopic lubricity reaching a coefficient of friction of 0.01. The rigid 3D molecular interlocking groups (molecular bearing: triaminotriptycene, additive) create nanostructures by bonding (stabilizer: Meisenheimer complexation) to the 3,5‐dinitrophenyl‐functionalized graphene. Mechanical shearing converts these graphene composites into highly stable surface‐bound tribolayers with a coefficient of friction (COF) of ≈0.01.