Adsorption of fluorinated ethers and alcohols on graphite

As part of a research program to determine the nature of the interactions o f perfluoropolyalkyl ether lubricants with the surfaces of magnetic data st orage media, we have studied the desorption of several model compounds from the surface of graphite. In this instance we have been modeling the chemic al functionality of the lubricant Fomblin Zdol by using perfluorodiethyl et her ((CF3CF2)(2)O) to represent the ether linkages of its backbone and 2,2, 2-trifluoroethanol (CF3CH2OH) to represent its hydroxyl end groups. The des orption kinetics of these compounds from the basal plane of graphite have b een compared with those of their hydrocarbon analogues (CH3CH2)(2)O and CH3 CH2OH. More importantly, the desorption of these compounds from graphite ha s been compared with prior measurements of their desorption from numerous t ypes of amorphous carbon films. The desorption from graphite occurs with ze ro-order kinetics and well-defined desorption energies. The results of thes e measurements indicate that the broad distributions of desorption energies observed on amorphous carbon films are due to heterogeneity of the carbon films rather than lateral interactions between adsorbed species. The nature of the interactions of the ethers and alcohols with the graphite surface i s consistent with previously proposed models for the interactions of fluori nated ethers and fluorinated alcohols with amorphous carbon films.