Dresden 2017 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 15: Solid-Liquid Interfaces: Structure, Spectroscopy II

O 15.4: Vortrag

Montag, 20. März 2017, 15:45–16:00, WIL B321

In-situ tracking of the dynamic structure evolution in nanometer confined liquids by combining X-Ray Reflectivity and white light interferometry in a surface forces apparatus — •Sadhanaa Buvaneswaran1, Henning Weiss2, Hsiu-Wei Cheng1, Claudia Merola1, Julian Mars2, Markus Mezger2, and Markus Valtiner11Max-Planck-Institut fur Eisenforchung GmbH — 2Max-Planck-Institut fur Polymerforchung

Nanometer confined liquids between solids exhibit molecular ordering and find importance in friction and energy conversion. How this structuring reacts to external triggers such as sliding of surfaces against each other, or changing applied stresses is notoriously hard to measure in experiment. Here, we experimentally obtain the structural information under precisely controlled liquid confinement with dynamically changing conditions. For this, we combine the Surface Force Apparatus which allows quantification of applied forces between two opposing surfaces based on optical interference and XRR that determines crystallographic structure on a molecular scale. A pore(mm2 area) with controlled height of only 100s of nm of a model liquid crystal 8CB could be realized. When no force is applied, X-Ray scattering (probed horizontal direction) showed a sharp peak at q=2nm-1 which agreed well with the calculated molecular length established in previous literature. In XRR (investigated vertical liquid layering) similar intensities at identical q indicated isotropic behavior. However, during dynamic straining, the scattering intensities were 180 degree out-of-phase to the reflectivity intensity pointing towards anisotropic behavior.

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