Berlin 2005 – scientific programme
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CPP: Chemische Physik und Polymerphysik
CPP 30: POSTER: Chemical physics
CPP 30.27: Poster
Tuesday, March 8, 2005, 16:30–18:30, Poster TU D
Phase behavior of confined asymmetric binary liquid mixtures: Theoretical analysis of experimental data — •Dirk Woywod, Gernot Rother, Sebastian Schemmel, Gerhard H. Findenegg, and Martin Schoen — Stranski-Laboratorium, TU Berlin, Sekr. TC 7,Straße des 17. Juni 124, 10623 Berlin
We investigate the phase behavior of an asymmetric binary liquid mixture between two planar homogenous substrates (slit pore). We employ a lattice-gas model and a mean-field approximation to obtain a closed expression for the grand potential.
This model is applied to study the phase behavior and microscopic
structure of a iso-butyric acid (iBA) + heavy water (D2O) liquid
mixture confined to mesoporous silica matrices (CPG-10).
Confinement-independent model parameters are adjusted to match the
experimental coexistence curve in the bulk. Since the pore liquid is
in equilibrium with an external reservoir we can also fix the
thermodynamic state in the model. By choosing appropriate values of
the pore width and the attraction strength between substrates and
water we analyze the impact of confinement on the phase diagram. Apart
from a depression of the liquid+liquid critical point we observe
surface-induced phase transitions as well as water adsorption by the
walls [1]. The theoretical predictions are supported by differential
refractometry data and small-angle
neutron scattering measurements.
[1] D. Woywod, S. Schemmel, G.H. Findenegg, and M. Schoen,
J. Chem. Phys., (sub. 2004)