DLVO theory definition

Surface forces Colloidal forces DLVO theory Definition... 

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... 

The experimentally observed fact that a definite surfactant concentration is needed to overcome the barrier nmax of disjoining pressure deserves attention [323,332], This is one of the main conditions in the CBF/NBF transition which is not considered by the DLVO-theory (see Section 3.4.3). 

Consider now coalescence taking into account the molecular and electrostatic forces. Of the greatest interest is dependence of stability factor F on parameters k, //, Sa, Sr, t, y, a, and definition of the criterion for transition from slow to fast coagulation. In Section 11.5 the condition of transition from slow to fast coagulation was considered within the framework of DLVO theory of identical colloid particles without taking into account hydrodynamic interaction... 

At separation distances of less than about 30 A, solvation forees and other effects of molecular structure sometimes eause large deviations from the predictions of DLVO theory. At very small separation distances, for instanee, oscillatory forces are sometimes observed that are evidently associated with the ease of paeking molecules between the two surfaees (Christenson et al., 1982 Israelach-vili, 1991 Ninham, 1980). At certain definite separation distanees, molecular... 

The derivative -dAa h)/dh = is the force per unit cross-sectional area, also known as Derjaguin s disjoining pressure [4,5], Within the context of this definition, both Ao(/t) and W(fi) are positive in the case of a repulsion and negative in the case of an attraction. Molecular attraction forces prevail at long distances, while repulsive forces prevail at very short distances (the so-called Born repulsion). The principal theory that describes the interactions in a thin film is the well-known Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, which focuses on the analysis of the competitive contribution of molecular (dispersion) attractive forces and electrostatic repulsion to the interaction between surfaces separated by a liquid film. 

All these observations and results verify the validity of the DLVO theory, considering especially that the theoretical and experimental definitions of... 

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. 

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