Professor Ludwik Leibler Matière Molle et Chimie
Ecole Supérieure de Physique et Chimie Industrielles, Paris
"Electric Field Induced Phase Transitions"
The classic phenomenon of phase separation in liquid mixtures has been widely studied for decades and both its thermodynamic and dynamic aspects are very well understood. The effect of uniform electric fields on the liquid phase separation has also attracted considerable attention in the last 50 years. And yet, even the question of whether the field favours mixing or demixing is still a subject of debate. Theories, going back to Landau predict field induced phase separation whereas most experiments, going back to Debye seem to show that uniform electric fields favour mixing. Yet, even for mixtures with a large dielectric constant mismatch, the effect is detectable only very close to the transition temperature, at about few hundredths of degree or less. Here, we predict and demonstrate that electric field can induce phase separation in mixtures of simple liquids under practical conditions provided it is non-uniform. For a mixture of paraffin and silicone oil, for example, applying a voltage of 100 Volts across unevenly spaced electrodes about 50 microns apart produces demixing at temperatures 1K above Tt. The phase separation is reversible: when field gradients are turned off the mixture becomes homogeneous again. The geometry of the electrodes controls the length-scale at which demixing occurs. This effect is ideally suited for various nanotechnological applications since it benefits from field gradients near small conducting objects. It also could have interesting implications for forming and using nanostructured patterns in polymer based systems.
* Work done in collaboration with Yoav TSORI and François TOURNILHAC.
BRIEF ACADEMIC/EMPLOYMENT HISTORY:
Ph.D. Physics, Warsaw University 1976
Collège de France, Paris Post-doctoral Fellow with Professor de Gennes 1977-1978
Centre d'Etudes Nucléaires, SaclayJoliot-Curie Fellow 1978-1979
Centre de Recherches sur les Macromolécules, Strasbourg Chargé de Recherches au CNRS 1979-1982
University of California, San Diego
Visiting Scientist 1982-1983
Centre de Recherches sur les Macromolécules, Strasbourg
Chargé de Recherches au CNRS 1983-1984
Ecole Supérieure de Physique et Chimie Industrielles, Paris (ESPCI) Director of Research of CNRS (1st Class)
1991-1996, Director of Research of CNRS (2nd Class) 1985-1991, Chargé de Recherches au CNRS 1984-1985
Ecole Supérieure de Physique et Chimie Industrielles, Paris (ESPCI) Professor of Soft Matter and Chemistry 2001-present, Director of Research (1st Class) at CNRS 2001-present, Director, ATOFINA-CNRS-ESPCI
Joint Research Laboratory (UMR 167) 2001-present