Electrical double layer interactions

The situations would be totally different when the two surfaces are put in electrolyte solutions. This is because of formation of the electrical double layers due to the existence of ions in the gap between solid surfaces. The electrical double layers interact with each other, which gives rise to a repulsive pressure between the two planar surfaces as... 

Electrostatic and electrical double-layer interactions also create new opportunities in science and technology. We have already seen an example of this in a vignette in Chapter 1 on electrophoretic imaging devices, and another, on electrophotography, is described in the next... 

Ideally, lyophobic sols are stabilised entirely by electric double-layer interactions and, as such, present colloid stability at its simplest. 

Macromolecular solutions are stabilised by a combination of electric double layer interaction and solvation, and both of these stabilising... 

Lyophilic colloids can also be desolvated (and precipitated if the electric double layer interaction is sufficiently small) by the addition of non-electrolytes, such as acetone or alcohol to aqueous gelatin solution and petrol ether to a solution of rubber in benzene. 

Two classes of interactions are considered (i) London-van der Waals attractions and (ii) electrical double-layer interactions. The unretarded London-van der Waals potential Ad between a sphere and a plate is 5i 6... 

Figure 3. Particle-polymer brushed surface interaction profile, (a) particle-surface contact (b) dispersion interaction (c) electrical double layer interaction osmotic polymer-brush particle interaction.

The electrical double layer interaction is a key feature of a great many colloidal systems that are of technological significance. In the preparation and useful shelf-life of paints, and/or inks, or in the area of detergency where the properties of charged surface active compounds come into consideration the stabilizing influence of the edl interaction is important. Special mention... 

In this chapter, we give exact expressions and various approximate expressions for the force and potential energy of the electrical double-layer interaction between two parallel similar plates. Expressions for the double-layer interaction between two parallel plates are important not only for the interaction between plate-like particles but also for the interaction between two spheres or two cylinders, because the double-interaction between two spheres or two cylinders can be approximately calculated from the corresponding interaction between two parallel plates via Deijaguin s approximation, as shown in Chapter 12. We will discuss the case of two parallel dissimilar plates in Chapter 10. 

In this chapter, we give approximate analytic expressions for the force and potential energy of the electrical double-layer interaction two soft particles. As shown in Fig. 15.1, a spherical soft particle becomes a hard sphere without surface structures, while a soft particle tends to a spherical polyelectrolyte when the particle core is absent. Expressions for the interaction force and energy between two soft particles thus cover various limiting cases that include hard particle/hard particle interaction, soft particle/hard particle interaction, soft particle/porous particle interaction, and porous particle/porous particle interaction. 

A linear relationship exists between the ESA or CVP amplitude and the volume fraction of the suspended particles. At relatively high-volume fractions, hydrodynamic and electric double-layer interactions lead to a non-linear dependence of these two effects on volume fraction. Generally, non-linear behavior can be expected when the electric double-layer thickness is comparable to the interparticle spacing. In most aqueous systems, where the electric double layer is thin relative to the particle radius, the electro-acoustic signal will remain linear with respect to volume fraction up to 10% by volume. At volume-fractions that are even higher, particle-particle interactions lead to a reduction in the dynamic mobility. 

When the electrostatic stabilization of the emulsion is considered, the electrolytes (monovalent and divalent) added to the mixture are the major destabilizing species. The zeta potential of the emulsion particles is a function of the concentration and type of electrolytes present. Two types of emulsion particle-electrolyte (ions) interaction are proposed non-specific and specific adsorption.f H non-specific adsorption the ions are bound to the emulsion particle only by electrical double-layer interactions with the charged surface. As the electrolyte concentration is increased, the zeta potential asymptotes to zero. As the electrostatic repulsion decreases, a point can be found where the attractive van der Waals force is equal to the repulsive electrostatic force and flocculation of the emulsion occurs (Fig. 9A). This point is called the critical flocculation concentration (CFC). 

In concentrated suspensions many body interactions between the colloidal particles determine the effective colloid-colloid interaction. Beresford-Smith and Chan (1983) [37] showed that in that case the effective colloid-colloid interaction can nevertheless be described by an effective pair interaction energy to characterise the electrical double layer interaction. This pair interaction energy also has a screened Coulomb form just as in the classical DLVO theory but the Debye screening parameter k now depends on the intrinsic coxmterion concentration and the concentration of added electrolyte in the system. This makes the effective pair energy dependent on the volume fraction of the particles (see general discussion of the paper of Beresford-Smith and Chan [38]. 

B. Beresford-Smith and D. Chan, Electrical double layer interactions in concentrated systems. Faraday Discuss. Chem. Soc., 76 (1983) 65-75. 

Chan, D.Y.C. A simple algorithm for calculating electrical double layer interactions in asymmetric electrolytes. Poisson-Boltzmann theory. J. Colloid Interface Sci. 2002, 245 (2), 307-310 Devereeux, O.F. deBruyn, P.L. Interaction of Plane Parallel Double Layers, MIT Press Cambridge, 1963. 

Chan, B.K.C. Chan, D.Y.C. Electrical doublelayer interaction between spherical colloidal particles an exact solution. J. Colloid Interface Sci. 1983, 92 (1), 281-283 Palkar, S.A. Lenhoff, A.M. Energetic and entropic contributions to the interaction of unequal spherical double layers. J. Colloid Interface Sci. 1994, 165 (1), 177-194 Qian, Y. Bowen, W.R. Accuracy assessment of numerical solutions of the nonlinear Poisson-Boltzmann equation for charged colloidal particles. J. Colloid Interface Sci. 1998, 201 (1), 7-12 Carnie, S.L. Chan, D.Y.C. Stankovich, J. Computation of forces between spherical colloidal particles Nonlinear Poisson-Boltzmann theory. J. Colloid Interface Sci. 1994, 165 (1), 116-128 Stankovich, J. Carnie, S.L. Electrical double layer interaction between dissimilar spherical colloidal particles and between a sphere and a plate nonlinear Poisson-Boltzmann theory. Langmuir 1996,12 (6), 1453-61. 

Colloidal particles are subjected to a number of attractive and repulsive forces and the stability of dispersions depends on the interplay of these various forces. The van der Waals attractive forces between particles have their origin in the electron wave fluctuations and are usually effective at close ranges. Electrical double layer interactions stem from the presence of ionized species at the interface and are effective at distances proportional to the double layer thickness for the given... 

The structure factor, S(Q), is determined by the nature of the particle interaction potential [7] for noninteracting systems 5 (Q) = 1 (viz., for systems in the limit of very low concentration where electrical double-layer interactions are negligible). 

Electrical Double Layer Interaction and DLVO Theory... 

The free energy of interaction of two interacting bodies may be expressed as a sum of electrical double layer interaction energy (in general, repulsive) and the van der Waals attraction energy (in general, attractive) ... 

Electrical Double Layers Interaction, Fig. 1 Two parallel plates with constant surface potentials... 

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