Deryaguin, Landau, Verwey, Overbeek

When speculating about the colloidal stability of a monomer droplet dispersion in water, one could use the Deryaguin-Landau-Verwey-Overbeek theory, also known as DLVO theory, to analyze the stability of the system. This has been done in Fig. 10a, where we show the effect of different surface potentials upon the rate of coagulation, fi, defined in the case of two droplets of the same size as ... 

The physical stability of a colloidal system is determined by the balance between the repulsive and attractive forces which is described quantitatively by the Deryaguin-Landau-Verwey-Overbeek (DLVO) theory. The electrostatic repulsive force is dependent on the degree of double-layer overlap and the attractive force is provided by the van der Waals interaction the magnitude of both are a function of the separation between the particles. It has long been realized that the zeta potential is a good indicator of the magnitude of the repulsive interaction between colloidal particles. Measurement of zeta potential has therefore been commonly used to assess the stability of colloidal systems. 

Deryaguin-Landau-Verwey-Overbeek (DLVO) Theory... 

The combination of G i and G results in the well-known theory of stability of colloids, that is the Deryaguin-Landau-Verwey-Overbeek (DLVO) theory [8-11],... 

Combination of Ga and G at various h results in the energy-distance curve is illustrated in Figure 11.34, which forms the basis of the Deryaguin-Landau-Verwey-Overbeek theory colloid stability (DLVO theory) [38]. 

This presentation forms the basis of the theory of colloid stability due to Deryaguin-Landau-Verwey-Overbeek (DLVO theory) [10]. The Gj-h curve shows two minima and one maximum A shallow minimum (of the order of few kT) units at large separations, which may result in weak and reversible flocculation. A deep primary minimum (several lOOkT units) is seen at short separations - this results in strong flocculation (coagulation). An energy maximum, G ax, at intermediate distances prevents flocculation into the primary minimum. 

The most widely used theory of the stability of electrostatically stabilized spherical colloids was developed by Deryaguin, Landau, Verwey, and Overbeek (DLVO), based on the Poisson-Boltzmann equation, the model of the diffuse electrical double layer (Gouy-Chapman theory), and the van der Waals attraction [60,61]. One of the key features of this theory is the effective range of the electrical potential around the particles, as shown in Figure 25.7. Charges at the latex particles surface can be either covalently bound or adsorbed, while ionic initiator end groups and ionic comonomers serve as the main sources of covalently attached permanent charges. 

The combination of van der Waals attraction and double layer repulsion results in the well-known theory of colloid stability due to Deryaguin, Landau, Verwey and Overbeek (DLVO theory) [6, 7]. 

The DLVO theory, a quantitative theory of colloid fastness based on electrostatic forces, was developed simultaneously by Deryaguin and Landau [75] and Verwey and Overbeek [76], These authors view the adsorptive layer as a charge carrier, caused by adsorption of ions, which establishes the same charge on all particles. The resulting Coulombic repulsion between these equally charged particles thus stabilizes the dispersion. This theory lends itself somewhat less to non-aqueous systems. 

Deryaguin, B. V. Landau, L. Acta Physicochim. UPSS 1941,14, 633. Verwey, E. J. Overbeek, J. Th. G. Theory of stability oflyophobic colloids-, Elsevier Amsterdam, 1948. 

When charged colloidal particles in a dispersion approach each other such that the double layers begin to overlap (when particle separation becomes less than twice the double layer extension), then repulsion will occur. The individual double layers can no longer develop unrestrictedly, as the limited space does not allow complete potential decay [10, 11]. The potential v j2 half-way between the plates is no longer zero (as would be the case for isolated particles at 00). For two spherical particles of radius R and surface potential and condition x i <3 (where k is the reciprocal Debye length), the expression for the electrical double layer repulsive interaction is given by Deryaguin and Landau [10] and Verwey and Overbeek [11],... 

---