A Macro and Nanoconfined Tribological Study of Linear and Branched Molecules

Elucidating the lubricity of a liquid under nanoconfinement conditions and associating it with the resulting macroscopic properties are important in the design of high-performance lubricants. One of interesting elements of regulating lubrication is branched structures as potential lubricants because the most popular base lubricant, poly(α-olefin) (PAO), possesses a branched structure. However, lubricants with such specific structures have never been systematically investigated. Thus, using macro friction measurements and resonance shear measurements, we investigated the macro and nanoconfined lubricities of branched potential lubricants, isostearic acid and isostearic acid T, and compared their properties with those of a typical branched lubricant (PAO) and a linear model lubricant (hexadecane) to elucidate the differences resulting from their different structures. It was found that the viscosity parameter ( b s ) at the smallest thickness, that called the hard wall thickness (normal load = 22.7 mN), of the confined liquid between surfaces increased in the order of isostearic acid