Surface polarization effects in confined polyelectrolyte solutions

Abstract

Understanding nanoscale interactions at the interface between two media with different dielectric constants is crucial for controlling many environmental and biological processes, and for improving the efficiency of energy storage devices. In this contributed paper, we show that polarization effects due to such dielectric mismatch remarkably influence the double-layer structure of a polyelectrolyte solution confined between two charged surfaces. Surprisingly, the electrostatic potential across the adsorbed polyelectrolyte double layer at the confining surface is found to decrease with increasing surface charge density, indicative of a negative differential capacitance. Furthermore, in the presence of polarization effects, the electrostatic energy stored in the double-layer structure is enhanced with an increase in the charge amplification, which is the absorption of ions on a like-charged surface. We also find that all of the important double-layer properties, such as charge amplification, energy storage, and differential capacitance, strongly depend on the polyelectrolyte backbone flexibility and the solvent quality. These interesting behaviors are attributed to the interplay between the conformational entropy of the confined polyelectrolytes, the Coulombic interaction between the charged species, and the repulsion from the surfaces with lower dielectric constant.

Image-charge effects on ion adsorption near aqueous interfaces

“…We hope this work stimulates such development which fully accounts for both molecular and surface polarization effects as well as ICI for both the ions and the solvents. An anticipated extension of our work is to study polyelectrolyte adsorption near dielectric interfaces, where simulations using implicit solvation model has shown the importance of the surface polarization effect (84). Also warranted are new simulation studies accounting for the ICI on graphene oxide membranes under electrostatic potential, which has received great attention as desalination membrane (85,86).…”

Structures of cationic and anionic polyelectrolytes in aqueous solutions: the sign effect

“…4,6 Specifically, the long-range electrostatic correlations between the charged monomers and released counterions largely determine the physicochemical natures of the polyelectrolyte solutions. 11–16 Moreover, the dipolar solvent molecules can solvate the ionic species through charge–dipole interactions. This effect is termed “ion solvation”, which was firstly proposed by Debye a century ago and has been extensively studied in the past few decades.…”

Unexpected Inverse Correlations and Cooperativity in Ion-pair Phase Transfer

“…Surface sensitive experimental techniques like vibrational sumfrequency generation (VSFG) 11,12 and X-ray diffraction 13 can provide an ensemble average depiction of molecular orientation and species distributions, however these do not characterize dynamic phenomena. [14][15][16] The instantaneous water/oil interface is oen interpreted in terms of capillary waves that derive from thermal uctuations and interfacial anisotropy, 13,17 yet on top of this rough and dynamically evolving surface other architectures have been predicted that are modulated by the presence of surfactants. These include protrusions that extend from the aqueous to organic phase, "islands" of surfactant bilayers, and budding micellar-like structures.…”