Charge regulated surfaces

Shubin V, Linse P. Self-consistent field modeling of polyelectrolyte adsorption on charge-regulating surfaces. Macromolecules 1997 30 5944—5952. 

Charge regulated surfaces In reality, most surfaces display an intermediate behaviour between constant charge and constant potential. For example, silica (Si02) can develop surface charge by both site dissociation and ion adsorption ... 

Dan, N. 2002. Interactions between charge-regulating surface layers. Langmuir 18, no. 9 3524-3527. doi 10.1021/la011147m. 

S. H. Behrens and M. Borkovec, Phys. Rev. E, 60, 7040 (1999). Exact Poisson-Boltzmann Solution for the Interaction of Dissimilar Charge-Regulating Surfaces. 

It is possible to calculate Vr as a function of separation exactly using numerical techniques. The method of Chan et al. 145] may be used for this purpose. Interested readers are referred to Ref. 45 for further information about these calculations. It is also possible to calculate the interaction for the charge regulation case where knowledge of the surface density of acid groups and their dissociation constants is required. 

If the dissociation of the ionizable groups on the particle surface is not complete, or the configurational entropy Sc of adsorbed potential-determining ions depends on N, then neither of ij/o nor of cr remain constant during interaction. This type of double--layer interaction is called charge regulation model. In this model, we should use Eqs. (8.35) and (5.44) for the double-layer free energy [ 11-13]. 

Beyond this, the inclusion of the competition for surface sites of different competing species (e.g. H vs. Na" ") gives rise to the further problem of surface charge regulation [22, 27-30], with a concomitant appearance of a so-called "secondary hydration force". Surface localised dipole-dipole correlations give rise to a further force [31, 32], and much of what was confused falls into place. These developments represent a first conceptual step forward on the way to a more complete and necessary stage of... 

Zhmud, B.V. and Sonnefeld, J., Charge regulation at the surface of porous silica,... 

The electrostatic properties of particles can be described by two key parameters, the surface charge density and the kinetic surface potential. The surface charge density (a,) corresponds to the potential at the particle surface ( /o). This charge regulates the interaction of dissolved ions with the surface and the effective charge is dependent on the degree of adsorbed counterions to the surface. In this section we discuss the relative effect of simple ions (no deprotonation and no condensation of aquo ligands) on sol stability when the pH is varied. 

Shubin, V, Samoshina, Y, Menshikova, A. and Evseeva, T., Adsorption of cationic polyelectrolyte onto a model carboxylic latex and the influence of adsorbed polvcation on the charge regulation at the latex surface. Colloid Polym. Sci., 275(7), 655,1997. 

Which boundary condition is more realistic depends on the materials used. In addition, the electrolyte and the speed of the approach might have an influence. Prica and coworkers measured force curves between 2irconia, which showed a constant charge behavior [84]. Also the force between two surfaces coated with densely packed carboxylic groups followed constant charge conditions [94]. In other cases, constant potential conditions are more appropriate. Most cases, however, lay between the two extremes. Then often, a charge regulation model is applied [156]. 

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