ABSTRACT
The bonding kinetics for 10 A Z-Tetraol films on the amorphous nitrogenated carbon surface (CNx) is investigated as a function of the Z-Tetraol molecular polarity. Z-Tetraol nominally contains 2 hydroxyl groups per chain end. The molecular polarity of Z-Tetraol is varied by the addition of a "bis-adduct" component of Z-Tetraol. This material contains 3 instead of 2 hydroxyl groups per chain end. The bonding kinetics and changes in the surface energy as a function of time in thin film mixtures is investigated under ambient conditions. The initial bonded fraction scales with the bis-adduct concentration and can be increased by as much as 50%. The asymptotic bonded fraction exhibits a more modest increase of approximately 10%.
ABSTRACT
The thermodynamic stability of boundary lubricant films based upon mixtures of liquid perfluoropolyethers (PFPEs) is reported. Mixtures of A20H-2000 with Zdols 2000, 2500, and 4000 and Zdol-TX 2200 on amorphous carbon nitride films are investigated. An optical surface analyzer is used to image the autophobic dewetting of the mixture PFPE films. The critical dewetting thickness coincides with the monolayer thickness of the adsorbed mixture PFPE films as determined by the changes in the surface energy as a function of lubricant film thickness. The critical dewetting thickness varies linearly with mixture concentration.
ABSTRACT
The thermodynamic stability of thin films of the perfluoropolyether (PFPE) Z-Tetraol, as a function of molecular weight, on amorphous nitrogenated carbon, CNx, is investigated. An optical surface analyzer is used to image the autophobic dewetting of the Z-Tetraol films. Film dewetting results when the PFPE film thickness applied to the CNx surface exceeds a critical value. This critical dewetting thickness is identified as the monolayer thickness of the adsorbed PFPE film via measurements of the changes in the surface energy as a function of lubricant film thickness. The observed dewetting coincides with the film thickness at which the disjoining pressure goes to zero. The critical dewetting thickness is dependent on the PFPE molecular weight.
