Derjaguin, Landau, Verwey and

BA Matthews, CT Rhodes. Use of the Derjaguin, Landau, Verwey and Overbeek theory to interpret pharmaceutical suspension stability. J Pharm Sci 59 521-525, 1970. 

The pair potential of colloidal particles, i.e. the potential energy of interaction between a pair of colloidal particles as a function of separation distance, is calculated from the linear superposition of the individual energy curves. When this was done using the attractive potential calculated from London dispersion forces, Fa, and electrostatic repulsion, Ve, the theory was called the DLVO Theory (from Derjaguin, Landau, Verwey and Overbeek). Here we will use the term to include other potentials, such as those arising from depletion interactions, Kd, and steric repulsion, Vs, and so we may write the total potential energy of interaction as... 

Roughly 60 years ago Derjaguin, Landau, Verwey, and Overbeek developed a theory to explain the aggregation of aqueous dispersions quantitatively [66,157,158], This theory is called DLVO theory. In DLVO theory, coagulation of dispersed particles is explained by the interplay between two forces the attractive van der Waals force and the repulsive electrostatic double-layer force. These forces are sometimes referred to as DLVO forces. Van der Waals forces promote coagulation while the double layer-force stabilizes dispersions. Taking into account both components we can approximate the energy per unit area between two infinitely extended solids which are separated by a gap x ... 

The DLVO-theory is named after Derjaguin, Landau, Verwey and Overbeek and predicts the stability of colloidal suspensions by calculating the sum of two interparticle forces, namely the Van der Waals force (usually attraction) and the electrostatic force (usually repulsion) [19],... 

The fundamental understanding of electrostatic interactions in aqueous media is still incomplete, particularly when the interacting surfaces are highly charged or the electrolyte in solution is not symmetric. However, since the pioneering work of Derjaguin, Landau, Verwey and Overbeek [1,2] some... 

The name, DLYO, originates from the first letter in the surname of the four authors (Derjaguin, Landau, Verwey and Overbeek) from two different groups, which originally published these ideas. The theory is based on the competition between two contributions, a repulsive electric double layer and an attractive van der Waals force [4,5]. The interaction in the electric double layer was originally obtained from mean field calculations via the Poisson-Boltzmann equation [Eq. (4)]. However, the interaction can also be determined by MC simulations (Sec. II. B) and by approximate integral equations like HNC (Sec. II. C). This chapter will focus on the first two possibilities. 

Application of DLVO Theory. Some of the concepts and expressions of Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory of colloid stabihty have been described in Chapter 1, or can be found in many different textbooks 4, 5). The application of DLVO theory to oil-in-water colloids with special reference to the stability of bitumen-in-water emulsions will be discussed here. 

For more than half of century the classical theories by Debye and Hiickel as well as by Derjaguin, Landau, Verwey and Owerbeek (DLVO) have been at the basis of theoretical physical chemistry and chemical engineering. The substantial progress in material science during last few decades as well as the advent of new instrumentation and computational techniques made it apparent that in many cases the classical theories break down. New types of interactions (e.g. hydrodynamic, entropic) have been discovered and a number of questions have arisen from theoretical and experimental studies. Many of these questions still do not have definite answers. 

Apparently, mechanisms of low-salinity waterflooding are related to the DLVO theory, which is named after Derjaguin, Landau, Verwey, and Overbeek. The theory describes the force between charged surfaces interacting through a liquid medium. It combines the effects of the van der Waals attraction and the electrostatic repulsion due to the so-called double layer of counter ions. 

Proteins adsorbed at an oil-water interface may stabilize the oil droplets by the Derjaguin, Landau, Verwey, and Overbeek (DLVO) interactions and/or the steric stabilization mechanism. The proteins may possess or be capable of adopting extended structures, which protrude into a solution for a considerable distance from the interface. This extended hydrated layer may form the basis for steric stabilization of the emulsion. Interactions between the adsorbed protein layers can involve a reduction in conhgurational entropy as molecular chains overlap (Darling and Birkett, 1987). In addition, hydration of adsorbed hydrophilic components can lead to an enthalpic repulsion when two particles are in close proximity. This tends to force the oil droplets apart (Darling and Birkett, 1987). 

Two approaching emulsion droplets may be resisted by electrostatic forces. Electrostatic forces consist of Coulombic repulsion between two like charged objects and attractive van der Waals forces. These two forces are accounted for by the Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory. A third force. Born repulsion, occurs at very small separation distances when electron clouds overlap [1,6,20,21], In emulsion systems an electrical double-layer may form around the disperse phase droplets. While electrical double-layer repulsion is certainly important in o/w emulsions, it does not play a large role in the stabilization of w/o emulsions due to the low dielectric constant of oil [55,56],... 

On the hypothesis developed by Derjaguin, Landau, Verwey, and Overbeek (DLVO), a colloidal suspension becomes rapidly unstable if the maximum value of random thermal energy of the colloidal particles. This hypothesis forms the basis of the DLVO theory of colloidal stability. With the approximate expression for

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Chapter 7 discusses the use of AFM to investigate the adhesion of particles to polymer surfaces. Adhesion of particles on membrane surfaces is the main cause of fouhng. In the beginning of the chapter, a short note on DLVO (Derjaguin, Landau, Verwey, and Overbeek) theory (a theory of the stability of colloidal dispersions) has been given. However, few studies of adhesion in the membrane field by AFM have been reported. The pioneer work of Bowen s school has been described. 

The DLVO theory, named after its founders Derjaguin, Landau, Verwey, and Overbeek, provides a quantitative description of the stability of lyophobic colloids. 

DLVO theory Theory explaining the balance of attractive and repulsive forces between particles in suspension. This theory is often used to explain the stability of a deflocculated suspension or the lack thereof. Acronymed for the four men who discovered and modeled this interaction Derjaguin, Landau, Verwey, and Overbeek. 

Derjaguin, Landau, Verwey, and Overbeek) theory addresses the interaction between pairs of particles based on the net influence of the repulsive forces that derive from the electrostatic forces, and the attractive forces that derive from van der Waals forces (Elimelech et al., 1998). The electrostatic forces act over relatively long distances, and result from the charge resident on the surface of the particles. The attractive van der Waals forces result from dipole—dipole interactions and act only at short distances. Thus, two particles that approach each other on a trajectory at separation distance, s, experience a combination of attractive, Vvdw. and repulsive, Vgs forces ... 

DLVO Derjaguin, Landau, Verwey, and Overbeek theory... 

In the 1940s Derjaguin, Landau, Verwey and Overbeek (DLVO), developed the hypothesis that the total particle interaction could be determined by simply summing the contributions from the van der Waals interaction and the EDL interaction. In the meantime, the DLVO theory has been widely verified experimentally. Furthermore, it has been found that many other forces may be combined in the same way to determine the overall interparticle interaction. Examples of some net interparticle interaction forces are shown in Figure 5.9. 

Colloidal systems are often governed by van der Waals interactions. This class of dipole, induced dipole, and dispersion interactions causes a ubiquitous attractive potential between the particles and the container walls and between the particles themselves, which must be balanced to produce a stable colloid. Stabilization of the suspension can be achieved using functional surface groups on the particles. They can induce repulsive electrostatic and steric interactions, which counterbalance the attractive potential. A self-contained description of electrostatically stabilized colloids in polar solvents was first given in the classical DLVO theory by Derjaguin, Landau, Verwey and Overbeek [26, 30]. 

In fact, there are several other theories proposed to explain the mechanisms by which microbial adhesion on a surface can take place. These include, but may not be limited to, the Derjaguin Landau Verwey and Overback (DLVO) theory (which involves considering the effects of hydrophobicity and surface charge) and the theory of thermodynamics of attachment (which involves surface-free energy). These theories and their different aspects have been explained elsewhere [50] and we will not introduce those details here. 

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