Molecular orientation of PFPE lubricant films and its quantification

The molecular orientation of piperonyl functional end groups (planar) of PFPE lubricants on carbon overcoat is investigated using FTIR (Fourier Transform Infrared). A molecular orientation index (MOI) is defined for the molecular orientation with respect to the disk surface. The MOI is found to be three times higher when all the planar end groups are perpendicular to the disk surface than for random orientation (MOI=1). The MOI strongly depends on process conditions for lubricant films thinner than similar to 5 nm. The wear durability of the lubricant films with the planar end groups preferably perpendicular to the carbon surface with MOI similar to 1.5 is found to be a few times better than those preferably parallel to the carbon surface with MOI < 1.