Dresden 2011 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 35: Poster: Micro- and Nanofluidics
CPP 35.3: Poster
Mittwoch, 16. März 2011, 17:00–19:00, P2
Molecular Orientational Order Phenomena in Boundary Layers observed in Nanopore Flows — •Simon Gruener1, Dominik Gerstner1, Yannick D. Kervran2, and Patrick Huber1 — 1Experimental Physics, Saarland University, Saarbruecken, Germany — 2Université de Rennes 1, Rennes, France
We present measurements on the spontaneous as well as the externally induced invasion of liquids into silica monoliths (porous Vycor) permeated by a tortuous pore network with radii on the scale of a few nanometers only. The dynamics are recorded upon varying the complexity of the liquid’s building blocks (mostly chain-like hydrocarbons). For the homologous series of non-polar alkanes we find boundary layers (i.e. immobile layers at the silica pore walls) composed of flat lying molecules with the thickness of one molecular diameter. However, switching to the series of polar 1-alcohols we detect a rearrangement of the molecular order in favor of pinned molecules being oriented perpendicular to the pore walls. This finding demonstrates the tendency to pair the polar hydroxyl groups of both the alcohol and the silica pore walls in order to minimize the system’s overall energy. The thickness of the boundary layer suggests a slanting of the molecules possibly due to the viscous drag exerted by the liquid flow in the pore center. This work has been supported within the DFG priority program 1164, Nano- & Microfluidics (Grant No. Hu 850/2).