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We look at the wetting of a pure fluid in contact with a charged flat surface. In the bulk, the fluid is a classical van der Waals fluid containing dissociated ions. The presence of wall and ions leads to strong dielectrophoretic and electrophoretic forces that increase the fluid's density at the wall. We calculate the fluid's profiles analytically and numerically and obtain the energy integrals. The critical surface potential for prewetting is obtained. In the phase diagrams, the line of first-order transition meets a second-order transition line at a critical point whose temperature can be higher or lower than the bulk critical temperature. The results are relevant to droplet nucleation around charged particles in the atmosphere and could possibly explain deviations from expected nucleation rates.

We deduce the mixing-demixing phase diagram for binary liquid mixtures in an electric field for various electrode geometries and arbitrary constitutive relation for the dielectric constant. By focusing on the behavior of the liquid-liquid interface, we produce simple analytic expressions for the dependence of the interface location on experimental parameters. We also show that the phase diagram contains regions where liquid separation cannot occur under any applied field. The analytic expression for the boundary "electrostatic binodal" line reveals that the regions' size and shape depend strongly on the dielectric relation between the liquids. Moreover, we predict the existence of an "electrostatic spinodal" line that identifies conditions where the liquids are in a metastable state. We finally construct the phase diagram for closed systems by mapping solutions onto those of an open system via an effective liquid composition. For closed systems at a fixed temperature and mixture composition, liquid separation occurs in a finite "window" of surface potential (or charge density). Higher potentials or charge densities counterintuitively destroy the interface, leading to liquid mixing. These results give valuable guides for experiments by providing easily testable predictions for how liquids behave in nonuniform electric fields.

We investigate the structure and phase behavior of the Stockmayer fluid in the presence of nonuniform electric fields using molecular simulation. We find that an initially homogeneous vapor phase undergoes a local phase separation in a nonuniform field due to the combined effect of the field gradient and the fluid vapor-liquid equilibrium. This results in a high-density fluid condensing in the strong field region. The system polarization exhibits a strong field dependence due to the fluid condensation.

We point out that a spatially varying electric field can be used to cancel the effect of gravity in liquid mixtures by coupling to the different components' permittivities. Cancellation occurs if the system under consideration is small enough. For a simple "wedge" electrode geometry we show that the required system size and voltage are practical, and easily realizable in the laboratory. Thus this setup might be a simple alternative to other options such as the space shuttle, drop-tower, or magnetic levitation experiments.

We argue that the presence of dissociated ions in block copolymers under electric fields can induce strong morphological changes and even lead to phase transitions. We investigate, in particular, diblock copolymers in the body centered cubic (bcc) phase. In pure dielectric materials (no free charges), a dielectric breakdown is expected to occur for large enough electric fields, preempting any structural phase transition. On the other hand, dissociated ions are predicted to induce a phase transition to a hexagonal array of cylinders, at fields of about 10 V/microm or even lower. The strength of this mechanism can be tuned by controlling the amount of free ions present.