Eur. Phys. J. E (2003) 12: 1-4
https://doi.org/10.1140/epjed/e2003-01-001-9

De-mixing dynamics of a binary liquid system in a controlled-pore glass

¹ Technische Universität Berlin, Stranski-Laboratorium, Strasse des 17.Juni 112, 10623 Berlin, Germany
² Laboratoire Léon Brillouin, (CEA-CNRS) CEA-Saclay, 91191 Gif-sur-Yvette, France
³ GKSS Forschungszentrum GeNF, Max Planck Strasse, 21502 Geesthacht, Germany

^* e-mail: thomas.hellweg@tu-berlin.de

Received: 1 January 2003
Published online: 5 November 2003

Abstract

The temperature-induced microphase separation of the binary liquid system iso-butyric acid+heavy water (iBA + D₂O) in a mesoporous silica glass (CPG-10-75) of nominal pore width 7.5 nm was investigated by neutron spin-echo spectroscopy (NSE) and neutron small-angle scattering (SANS). Two mixtures of different composition were studied at different scattering angles at temperatures above and below the bulk phase transition temperature. The phase separation in the pore space is found to occur at a lower temperature than the bulk transition and extends over a significant temperature range. The effective diffusion coefficient derived from NSE at low scattering angles is found to decrease by one order of magnitude from 70 ^∘C to 20 ^∘C. This observation is attributed to the growing size of concentration fluctuations having a cut-off at ca. 8 nm, which corresponds to the mean pore size. The dynamics of the concentration fluctuations appears to be strongly influenced by the confinement in the pores, as it differs strongly from the bulk behaviour. These results are consistent with the preliminary results of the SANS study.