We study the thermodynamic behavior of nonpolar liquid mixtures in the vicinity of curved charged objects, such as electrodes or charged colloids. There is a critical value of charge (or potential), above which a phase-separation transition occurs, and the interface between high- and low-dielectric constant components becomes sharp. Analytical and numerical composition profiles are given, and the equilibrium front location as a function of charge or voltage is found. We further employ a simple Cahn-Hilliard type equation to study the dynamics of phase separation in spatially nonuniform electric fields. We find an exponential temporal relaxation of the demixing front location. We give the dependence of the steady-state location and characteristic time on the charge, mixture composition and ambient temperature.
Bibliographical noteFunding Information:
We thank L. Leibler and F. Tournilhac for help in developing the ideas presented in this work, and D. Andelman for numerous useful comments. This research was supported by the Israel Science Foundation (ISF) Grant No. 284/05, and by the German Israeli Foundation (GIF) Grant No. 2144-1636.10/2006.