Electric Fields: From Copolymer Orientation to Phase-Transitions and Chemical Reactions in
Dept. of Chemical Engineering, Ben Gurion University
Electric field can have a strong effect in many soft-matter systems, such as liquids, polymers,
colloids, etc. We first show that an electric field can orient mesophases of
block-copolymers. Based on a so-called "dielectric mechanism", proportional to the
permittivity difference squared, external field can also provoke an order-order or
order-disorder phase-transition. However, generally the influence on the critical
temperature is quite small, since composition fluctuations couple with electric field
fluctuations. In contrast, spatially nonuniform fields can have a dramatic effect on the phase
behavior because of the direct coupling between composition fluctuations and externally-imposed
field gradients. The new type of phase-transitions is demonstrated for block-copolymers and
liquid mixtures in nonuniform electric fields, with and without dissociated ions.
We illustrate several important applications of these transitions in electric-field-controlled
lubrication and controlled chemical reactions.