Dramatic enhancement of wear stability in oil-enriched polymer gel nanolayers

We report results on microtribological studies of chemically grafted, nanoscale polymer layers with enhanced wear stability. A 8–10 nm thick polymer gel layer composed of an elastomer was chemically grafted to a solid substrate and saturated with paraffinic molecules with different lengths of alkyl chains (15–24 carbon atoms, molecular weight M=212–338). We studied the polymer layer ability to adsorb and held these paraffinic oils and considered to what extent the evaporation rate can be controlled by initial saturation and slower diffusion of longer alkyl chains. A microtribometer and a friction force microscope were used to accumulate the frictional characteristics and to study wear stability of the polymer layers. We observed that the presence of shorter chain paraffinic oil (C15H32 and C18H38) resulted in a lower value of the friction coefficient and higher wear resistance as compared to a dry polymer layer and a polymer gel layer with longer-chain paraffinic oil (C20H42 and C24H50). The approach of trapping mobile lubricants within a compliant nanoscale surface layer could lead to exceptionally robust molecular lubrication coatings for complex surface topography with developed nanosized features.