IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Magnetic Recording Topical Conference Wednesday Sessions
       Session MR+MI+AS+SE-WeM

Paper MR+MI+AS+SE-WeM9
Kinetics and Energetics of the Desorption of Polyether Lubricants

Wednesday, October 31, 2001, 11:00 am, Room 110

Session: Magnetic Recording: Tribology & Integration
Presenter: K.R. Paserba, Carnegie Mellon University
Authors: K.R. Paserba, Carnegie Mellon University
N. Prashanth, Carnegie Mellon University
A.J. Gellman, Carnegie Mellon University
Correspondent: Click to Email
Desorption or evaporation is one of the mechanisms for loss of perfluoropolyalkylether (PFPE) lubricants from the surfaces of data storage media. One approach to minimizing PFPE loss by desorption is the use of lubricants with increasing molecular weight or increasing average chain length. In order to understand the effects of chain length on the lubricant evaporation kinetics we have studied the desorption kinetics of monolayer films of oligomeric ethers with varying chain length adsorbed on the surface of graphite. This study has used monodispersed samples of oligomeric ethyleneglycol dimethylethers, CH3O(CH2CH2O)mCH3, and oligomeric ethyleneglycols, HO(CH2CH2O)mH, as models for the perfluoropolyalkylether lubricants Fomblin Z and Fomblin Zdol. Their adsorption and desorption from the surface of graphite has been measured as a function of chain length, M = 3m+3, or molecular weight by using thermally programmed desorption methods in ultra-high vacuum. The results of these measurements show the surprising result that the desorption energies, @DELTA@E@sub des@, are non-linear in the chain length. What is most interesting is that the desorption energies can be expressed by the power law expression @DELTA@E@sub des@ = a + b M@gamma@ with @gamma@ ~ 0.5. A model has been proposed for the desorption mechanism of such oligomeric lubricants from surfaces which can quantitatively reproduce the dependence of the desorption energies on chain length. The origin of the non-linearity is the conformational isomerism of the oligomers as they desorb from the surface. We will discuss the implications of these results on the desorption of oligomeric PFPE lubricants from the surfaces of magnetic data storage media.