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Langmuir 1992,8, 328-333
Effect of Substrate on Shearing Properties of Ultrathin Polymer Films S. J. Him,+A. M. Homola,*J G. Hadziioannou,§ and C. W. Frank? Department of Chemical Engineering, Stanford University, Palo Alto, California 94305, IBM Research Division, Almaden Research Center, 650 Harry Road, San Jose, California 95120, and Chemistry Department, University of Groningen, Groningen, The Netherlands Received November 26, 1990. I n Final Form: August 6, 1991 We have investigated the frictional behavior of molecularly smooth solid surfaces lubricated with a linear perfluoropolyether. The substrates used were mica and thin films (10 nm) of zirconia and alumina sputtered onto mica. The surface topography was determined by atomic force microscopy,and the relative surface energies were estimated from contact angle measurements. Sliding experiments were performed with a modified surface forces apparatus under both dry and humid conditions. In a dry environment, an ultrathin (
