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Condensed Matter Seminars

ics Condensed Matter
Thursday, April 20, 2000
4:00 PM
Physics Building, Room 204
Note special time.
Note special room.
Prof. Shenting Cui [Host: R. E. Johnson]
Dept. of Chemical Engineering at Univ. of Tenn. and Chemical Technology Div. at Oak Ridge Lab.
"Soft Matter in a Tight Spot: The Structural Transition and the Molecular Origin"
Phenomena occurring on nanometer scale are attracting increasing scientific interest due to the expected advances in nanotechnology. This talk will describe recent studies on the fluid behavior occurring at a few nanometers when one of the dimensions, the spacing between two solid surfaces, is reduced to a few molecular diameters. Such conditions are encountered in the operation of the computer magnetic disks, preparation of nano-structured materials, colloidal dispersions, and automobile lubrication, etc. When a fluid is confined within spacing comparable to the molecular dimension, interfacial interactions become predominant and this can dramatically alter the structural, thermodynamic and rheological properties of the fluid film. Experiments have found that solid-like behaviors develop for fluids confined between molecularly smooth mica surfaces. This is manifested by the ability of the film to sustain a finite stress, a phenomenon typically associated with solids, and orders of magnitude increase in viscosity. The microscopic mechanism for the phenomenon is still not well understood theoretically. We describe a comprehensive molecular simulation study that demonstrates the solid-like behavior for alkane films narrowly confined in molecularly smooth strong-adsorbing surfaces at ambient temperature and pressure. The results of the study correlate a broad range of experimental observations and point to a mechanism different from that has been previously suggested.

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