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Particle contamination at the head–disk interface (HDI) is a major concern for the long-term reliability of hard disk drives. In the current study, it is shown that, surprisingly, soft and lubricious talc particles have a significant damaging effect on the friction performance of media lubricants, nanometer-thick perfluoropolyethers. Thermogravimetric analysis (TGA) and the adsorption studies indicate that two mechanisms, Lewis acid–catalyzed decomposition and surface adsorption, are responsible for the observed tribological degradation. The potential impacts of the findings here on the design of next-generation media lubricant have been discussed.

The process of adsorption or “self-assembly” of surfactant monolayers and bilayers from solution onto molecularly smooth mica surfaces was monitored as a function of time. The time evolution of the molecular and ionic composition and densities of the layers were measured using XPS (ESCA); ionic concentrations were measured using an ion selective electrode (ISE); the structure and solution interactions of the layers were measured using the surface forces apparatus (SFA) technique; and the wettability and adhesive properties of the layers were measured via contact angle measurements. It was found that the adsorption or self-assembly of a monolayer or bilayer from solution always occurs in two distinct stages: a fast initial nonequilibrium stage, followed by a much slower phase involving slow molecular and ionic rearrangements toward the final equilibrium state. In the case of cationic surfactants adsorbing onto the anionic surface of mica, XPS measurements show that most of the surfactant molecules initially adsorb as dipoles (i.e., carrying their negatively charged counterions with them) onto the mica surface, which also partially retains its (positively charged) counterion. Following this, the oppositely charged counterions unite to form an ion pair that proceeds to slowly diffuse out of the headgroup region through the hydrophobic layer into the bulk solution, leaving behind headgroups that are now bound to the surface much more strongly via Coulombic (ionic) bonds rather than dipolar bonds. The effects of counterions, pH, and surfactant concentration on the mechanisms and kinetics of self-assembly were studied. In some cases the time needed to attain equilibrium was many months—the rate limiting step being the diffusion of the hydrophilic headgroups, ions, and ion pairs through the hydrophobic layers. Both the final equilibrium state and the various dynamic processes of self-assembly (toward that state) are interdependent and determined by a need to satisfy local electroneutrality conditions and not only by hydrophobic and molecular-packing considerations. The relevance of our findings to other surfactant adsorption systems, including Langmuir—Blodgett deposition, and self-assembly mechanisms in general is discussed.

Infrared and fluorescence spectroscopic methods were used to study the kinetics and thermodynamics of the formation of self-assembled films of n- alkanoic acids by adsorption from solutions. The adsorption of stearic acid from hexadecane solutions onto glass and aluminum substrates was shown to lead to monolayer formation. A Langmuir-type transient adsorption model was shown to be applicable to these systems. The stationary fluorescence spectroscopy of a pyrene-labeled alkanoic acid probe was also used to determine the relative values of the kinetic constants of various fatty acids having different number of carbons in the chains. A linear increase of approximately 230 cal/mole in the negative free energy of adsorption with increasing chain length of the fatty acids was found. This attributed to the energetic contribution of the molecular organization of the aliphatic chains to the self-assembly process.