Colloids charge stabilization

Behrens S H, Borkovec M and Schurtenberger P 1998 Aggregation in charge-stabilized colloidal suspensions revisited Langmuir 1951-4... 

Meijer, E. J. Azhar, F. El, Novel procedure to determine coexistence lines by computer simulation, application to hard-core Yukawa model for charge-stabilized colloids, J. Chem. Phys. 1997,106, 4678-4683... 

Temperature Sensitivity. Samples of Au-acetone colloid were subjected to boiling and freezing. Upon returning to room temperature the colloids remained stable and no flocculation had occurred. These results indicate that steric stabilization33,43) (solvation) is a very important mechanism. Charge-stabilized colloids generally flocculate when subjected to such extremes of temperature.(56)... 

In DLVO theory, the secondary minimum can only be created by the van der Waals force, which is essentially independent of the salt concentration across the concentration range 0.001 M < c < 0.1 M. This force has to be balanced with a force that decays exponentially as a function of k, which means that it decays by a factor exp(-10) across this range. The unhappy consequence of this prediction is that the position of the secondary minimum, and therefore the interlayer d value, varies very rapidly as a function of k, in contradiction to the experimental results. A further unhappy consequence of this balance is that it always produces a primary minimum much deeper than the secondary minimum. The full, standard DLVO thermodynamic potential energy curve, which also includes a very-short-range Bom repulsion, is shown in Figure 1.13 [23], It is therefore a definite prediction of DLVO theory that charge-stabilized colloids can only be kinetically, as opposed to thermodynamically, stable. The theory does not mean anything at all if we cannot identify the crystalline... 

Crocker JC, Grier DC. Interactions and dynamics in charge-stabilized colloids. Materials Research Society Bulletin 1998 23 24-31. 

Weiss JA, Larsen AE, Grier DG. Interactions, dynamics, and elasticity in charge-stabilized colloidal crystals. J Chem Phys 1998 109 8659-8666. 

As a practical application of the relationship in Equation (10.28), one may characterize the stability of a charge-stabilized colloidal system by its critical coagulation concentration (ccc), the concentration of electrolyte necessary to bring the system into the regime of rapid coagulation. The process involves the extrapolation of the curve of In IT versus In Co to In IT = 0, which gives In (ccc). However, what is the practical use of the ccc and what does it mean in theoretical terms ... 

E. Overbeck, C. Sinn, M. Watzlawek, Enhanced structural crmelations accelerate dillusion in charge-stabilized colloidal suspensions. Phys. Rev. E 60(2), 1936-1939 (1999). doi 10.1103/ PhysRevE.60.1936... 

A.K. Arora, B.V.R. Tata (eds.). Phase Transitions in Charge Stabilized Colloids (VCH Publishers, New York, 1996)... 

The Gibbs-Duhem integration method excels in calculations of solid-fluid coexistence [48,49], for which other methods described in this chapter are not applicable. An extension of the method that assumes that the initial free energy difference between the two phases is known in advance, rather than requiring it to be zero, has been proposed by Meijer and El Azhar [51]. The procedure has been used in [51] to determine the coexistence lines of a hard-core Yukawa model for charge-stabilized colloids. 

Steric stabilization of a colloidal dispersion is achieved by attaching long-chain molecules to colloidal particles (Fig. 3.6). Then when colloidal particles approach one another (for example due to Brownian motion), the limited interpenetration of the polymer chains leads to an effective repnlsion which stabilizes the dispersion against flocculation. Steric stabilization has several advantages compared to charge stabilization. First, the interparticle repulsion does not depend on electrolyte concentration, in contrast to charge-stabilized colloids where the electric double-layer thickness is very sensitive to ionic strength. Second, steric stabilization is effective in both... 

Latex dispersions have attracted a great deal of interest as model colloid systems in addition to their industrial relevance in paints and adhesives. A latex dispersion is a colloidal sol formed by polymeric particles. They are easy to prepare by emulsion polymerization, and the result is a nearly monodisperse suspension of colloidal spheres. These particles usually comprise poly(methyl methacrylate) or poly(styrene) (Table 2.1). They can be modified in a controlled manner to produce charge-stabilized colloids or by grafting polymer chains on to the particles to create a sterically stabilized dispersion. Charge-stabiHzed latex particles obviously interact through Coulombic forces. However, sterically stabilized systems can effectively behave as hard spheres (Section 1.2). Despite its simpHcity, the hard sphere model is found to work surprisingly well for sterically stabilized latexes. 

R. van Roij, M. Dijkstra, and J.-P. Hansen, Phys. Rev. E, 59,2010 (1999). Phase Diagram of Charge-Stabilized Colloidal Suspensions Van der Waals Instability without Attractive Forces. 

Subsequently, we take Pe, ko, and r as independent variables, and calcnlate the phase behavior in the three-dimensional space spanned by them. This choice is made for the sake of simplicity. In experimental charge-stabilized colloidal suspensions, all these variables depend on each other. Experimental parameters can be mapped on our phase diagrams by estimating the effective screening length Ka and contact value pe. Note that, in our phase diagrams, two phases in coexistence have equal pressure, chemical potential, xa, and pe, but different q. 

Sengupta S and Sood AK. 1991. Theory of liquid-bcc-fcc coexistence in charge-stabilized colloidal systems. Physical Review A 44 1233-1236. 

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