The Hydration Repulsion between Charged Surfaces as an Interplay of Volume Exclusion and Dielectric Saturation Effects

Abstract

by Israelachvili et al. (2,3) and Pashley (4,5), who examined We demonstrate that the hydration repulsion between smooth the validity of DLVO theory at small film thicknesses in expericharged surfaces can be attributed to the interplay of two effects ments with films from aqueous electrolyte solutions confined which are not taken into account in the conventional DLVO the-between two mica surfaces. At electrolyte concentrations below ory. These are the finite size of the counterions and the variable 10 04 M (KNO 3 or KCl) they observed the typical DLVO dielectric permittivity across the electric double layers. We involve maximum. However, at electrolyte concentrations higher than The physical importance of the hydration force is that it the presence of electrolyte at ionic strengths above 1 m M. ᭧ 1996 stabilizes some dispersions preventing coagulation in the Academic Press, Inc.primary DLVO minimum. It is believed that the hydration Key Words: counterion adsorption; dielectric saturation; hydra-force is connected with the binding of strongly hydrated tion energy of ions; hydration repulsion; surface force apparatus; ions at the interface. This is probably the explanation of the volume exclusion effect for ions.

Force measurements with the atomic force microscope: Technique, interpretation and applications

“…Several effects are discussed in the literature [477][478][479]. Certainly the fact that one layer of water molecules is bound to the solid surfaces is important.…”

Adsorption and capillary condensation in porous media: Liquid retention and interfacial configurations in angular pores

“…Some controversy exists regarding the origin of this structural component; some attribute it to changes in the structure (density) of water adjacent to solid surfaces and deformation of hydrated shells, while others attribute this force to the presence of a layer with a lower dielectric constant near the surface [Paunov et al, 1996]. Regardless of its exact origin, this component is responsible for the so-called hydration repulsion which stabilizes dispersion and prevents coagulation of some colloidal particles, even at high electrolyte concentrations [Mitlin and Sharma, 1993] the Hamaker constant for the various interactions.…”

Direct observation of self-assembled chain-like water structures in a nanoscopic water meniscus

“…These phenomena include assembly and function of biomolecules, [1][2][3] wetting and interfacial interactions, [4][5][6] corrosion processes, 7,8 condensation and crystallization of water vapor on surfaces, 3,[8][9][10][11][12][13] and amorphous solid water in an interstellar medium. 14 It has long been postulated that water in confined spaces can have dramatically different physical properties from bulk water in extended spaces.…”

“…3 These hydration layers also influence the chemical and mechanical properties of hydrophilic or hydrophobic surfaces such as oxides (silica, alumina, mica, clay, nano tubes, and graphite). 6,[19][20][21][22][29][30][31][32][33][34] Water is also a pervasive environmental component whose interactions with surfaces are critical to system performance in a wide range of emerging nano and other chemical and biological technologies.…”

“…[37][38][39] Although the effective Kelvin radii in their SEM images are strongly positive, water bridges remained highly stable in an ambient environment. 38 Nanomechanical measurements have demonstrated that the viscosity of water confined between the tip and the surface in air are shown to be ~10 6 times larger than the viscosity of water in extended spaces or bulk water. [40][41][42] Nanoscale studies found that the evaporation rate of capillary water was significantly less than that of bulk water, especially at low relative humidity (RH) values.…”