We study the thermodynamic behavior of nonpolar liquid mixtures in thevicinity of curved charged objects, such as electrodes or charged colloids. Forsmall enough charge on the object, or equivalently, small potential, thedielectrophoretic force leads to enrichment of the more polar liquid close thecolloid. However, there is a critical value of charge (or potential), abovewhich a phase-separation transition occurs, and the interface between high- andlow-dielectric constant components becomes sharp. Analytical and numericalcomposition profile are given, and the equilibrium front location as a functionof charge or voltage is found. We further employ a simple Cahn-Hilliard typeequation to study the dynamics of phase-separation in spatially nonuniformelectric fields. We find an exponential relaxation of the composition frontlocation, with a characteristic time depending on the charge, mixturecomposition and ambient temperature.
展开▼
