Towards self-lubricated nanocoatings

The microtribological performance of molecularly thick (<10 nm) thermoplastic elastomeric films grafted to a silicon surface was enhanced by adding a minute amount of paraffinic oil, which was adsorbed from vapor phase and held by the rubber matrix. We studied the kinetics of polymer swelling in oil and the formation of polymer gels. We observed that a vast majority of adsorbed oil evaporated from the ultrathin polymer coating leaving a minute amount of oil trapped within the rubber phase. This resulted in a dramatic enhancement of the microtribological performance of the grafted polymer gel layers. These polymer gel layers exhibited a very steady friction response and a small value of the coefficient of friction as well as greater wear-resistance as compared to the initial polymer coating. The performance of polymer gel coatings was much better than the performance of a classic ‘boundary lubricant’ for silicon surfaces, an alkylsilane self-assembled monolayer. The approach proposed demonstrated a new efficient route towards enhanced tribological performance of ultrathin polymer coatings.