Abstract Nicholas D. Spencer

Lubricating with polymer brushes in water and oil

Nature lubricates with water, but water is not, in itself, a good lubricant.  Natural lubricating systems, such as mucus, are only slippery by virtue of the glycoproteins that adsorb on the surfaces to be lubricated, maintaining a layer of water in close proximity to the surface, even in the presence of shear and moderate normal forces. This behavior can be mimicked by means of adsorbed polymer layers, and in particular polymer brushes, which form spontaneously when polymers are surface anchored at high grafting density in the presence of a good solvent. This approach has been used in our laboratory, the polymer chains being either attached pre-formed or grown out of the surface. The approach is not only highly effective in water, but it also works, with different polymers, in oil-based systems, imparting very low friction at low speed, where hydrodynamic lubrication mechanisms are no longer in operation. The synthesis and characterization of polymer brushes will be described, as well as their tribological properties in both oil and water.