Berlin 2012 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 36: Wetting, Micro and nanofluidics I

CPP 36.6: Talk

Thursday, March 29, 2012, 16:30–16:45, C 264

Dielectric Capillary Rise in Mesoporous Vycor-Glass — •Beatrice Hallouet, Erika Robert, Patrick Huber, and Rolf Pelster — FR 7.2 Experimentalphysik, Universität des Saarlandes, Campus E26, 66123 Saarbrücken

We present a new method to follow the capillary rise of liquids in mesoporous samples by means of dielectric spectroscopy. The mesoporous material is Vycor®, a 3D network with a mean pore radius of about 4 nm and a porosity of about 30 %. The liquids are 1-alcohols (hexanol up to undecanol) which are carbons-chains molecules with one polar group. By measuring the time dependence of the permittivity, we are able to show that the capillary rise follows the so-called Lucas-Washburn law h(t)=c_h √t, where c_h depends on fluid parameters (viscosity, surface tension) and matrix parameters ( porosity, radius ...). The combination of dielectric and gravimetric measurements allows us to evaluate quantities like the initial porosity or the hydrodynamic radius. We discuss the influence of humidity, i.e. of adsorbed water layers on the pore walls. The flow of all alcohols seems to be characterized by the same hydrodynamic radius but the contact angle may vary as a function of the chain length.