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Full-Text Articles in Physical Sciences and Mathematics
Double Layer In Ionic Liquids: Overscreening Versus Crowding, Martin Z. Bazant, Brian D. Storey, Alexei A. Kornyshev
Double Layer In Ionic Liquids: Overscreening Versus Crowding, Martin Z. Bazant, Brian D. Storey, Alexei A. Kornyshev
Brian Storey
We develop a simple Landau-Ginzburg-type continuum theory of solvent-free ionic liquids and use it to predict the structure of the electrical double layer. The model captures overscreening from short-range correlations, dominant at small voltages, and steric constraints of finite ion sizes, which prevail at large voltages. Increasing the voltage gradually suppresses overscreening in favor of the crowding of counterions in a condensed inner layer near the electrode. This prediction, the ion profiles, and the capacitance-voltage dependence are consistent with recent computer simulations and experiments on room-temperature ionic liquids, using a correlation length of order the ion size.
Tension-Induced Straightening Transition Of Self-Assembled Helical Ribbons, Yevgeniya V. Zastavker, Brice Smith, George B. Benedek
Tension-Induced Straightening Transition Of Self-Assembled Helical Ribbons, Yevgeniya V. Zastavker, Brice Smith, George B. Benedek
Yevgeniya V. Zastavker
Helical ribbons with pitch angles of either 11° or 54° self-assemble in a wide variety of quaternary surfactant-phospholipid/fatty acid-sterol-water systems. By elastically deforming these helices, we examined their response to uniaxial forces. Under sufficient tension, a low pitch helix reversibly separates into a straight domain with a pitch angle of 90° and a helical domain with a pitch angle of 16.5°. Using a newly developed continuum elastic free energy model, we have shown that this phenomenon can be understood as a first order mechanical phase transition.