COLL 113 |
| Greg D. Haugstad, Characterization Facility, Institute of Technology, University of Minnesota, 12 Shepherd Labs, 100 Union St. SE, Minneapolis, MN 55455, Ronald H. Schmidt, University of Lund, Lund, Sweden, Jon A. Hammerschmidt, Eastman Kodak, Rochester, NY, Craig Dykstra, 3M Company, St. Paul, MN, Susheng Tan, Department of Chemistry, Oklahoma State University, Stillwater, OK 74078, and Wayne L. Gladfelter, Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, MN 55455. |
| The application of cantilever-based, nanoprobe read/write devices for polymeric media, as well as thin-film polymer lubricants in confined geometries, will benefit from further understandings of the fundamentals of probe-polymer interactions. We have investigated these interactions on several polymeric systems and with several modes of scanning probe microscopy. Here we discuss findings on polydimethylsiloxane (PDMS), polymethyl methacrylate (PMMA) and polystyrene (PS) films. On PDMS films, with bulk viscosities spanning several orders of magnitude, we find a solid-like to liquid-like transition at film thicknesses of approximately three times the radius of gyration. This is manifest as an increase in sliding friction by two orders of magnitude, and concomitant outward wicking of polymer during probe retraction, above the transition thickness. On PMMA, the dissipative molecular motions excited near the surface, manifest as a friction force, have activation energies on the order of beta processes (as determined by Arrhenius analysis) and further imply surface-enhanced mobility. In contrast, segmental and whole-chain motions in PS near the glass transition during scan-induced patterning have activation energies on the order of alpha processes, but imply no enhancement of mobility. Shear-modulation Fourier analysis on PS at room temperature further reveals a molecular weight dependence in the linearity of nanoprobe-polymer interactions (stiction and plastic processes), including transitional behavior near the critical entanglement molecular weight. |
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Friction, Lubrication, and Adhesion in Micro- and Nano-Scale Devices
8:30 AM-12:00 PM, Monday, March 29, 2004 Marriott -- Orange County 5, Oral
Division of Colloid and Surface Chemistry |