Aqueous lubrication of polymers: Influence of surface modification

We have investigated the influence of surface modification of an elastomer, poly(dimethylsiloxane) (PDMS), on its aqueous lubrication properties. A dramatic reduction in frictional forces has been observed upon hydrophilization by oxygen-plasma treatment or by surface coating with amphiphilic co-polymers, when PDMS was slid against PDMS in an aqueous environment. This effect is attributed to the removal of the strong hydrophobic interaction between PDMS surfaces in water, thereby enabling the isoviscous-elastic lubrication (or soft EHL) mechanism to predominate. This study demonstrates the significance of surface modification in allowing effective soft EHL of an elastomer.