The Contribution of Thin PFPE Lubricants to Slider-Disk Spacing. 2. Effect of Film Thickness and Lubricant End Groups

We have investigated the effect of film thickness of a perfluoropolyether lubricant, Zdol 4000, on slider-disk spacing, or clearance. The major conclusion of this work is that the Zdol lubricant impacts the slider-disk spacing. A decrease in the film thickness of Zdol 4000 by ∼10Å results in an increase in the effective slider-disk spacing by ∼1 nm. The effect of end groups on slider-disk spacing is also investigated using the Zdol-TX and Z-Tetraol perfluoropolyether lubricants. At similar molecular weights and film thicknesses, the end groups do not affect the slider-disk spacing by causing any additional interference. The slider-disk interference is therefore attributed to the attractive van der Waals interaction between the slider and the disk surface that causes the Zdol main chain to interact with the slider surface, giving rise to a friction force.