Colloidal interactions repulsive steric forces

Five types of forces between colloidal particles may be identified (i) repulsive forces, from the overlap of electrical double-layers (ii) dispersion forces, from long-range van der Waals attraction between molecules in neighbouring particles (iii) steric forces, from interaction of macromolecules adsorbed at the particle surface (iv) structural and Brownian forces, from interaction with solvent molecules of the dispersion medium and (v) hydrodynamic forces. 

To distinguish between colloid stability/instability and physical stability one must consider the state of the suspension on standing as schematically illustrated in Fig. 3.39. These states are determined by (i) magnitude and balance of the various interaction forces, electrostatic repulsion, steric repulsion and van der Waals attraction (ii) particle size and shape distribution (iii) density difference between... 

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... 

Colloidal suspensions are often stabilized by the adsorption of polymers that are expected to exert additional configurational-steric repulsive forces. The additional, potentially significant van der Waals interactions between polymer coatings... 

In the theory developed by Derjaguin and Landau (24) and Verwey and Overbeek (25.) the stability of colloidal dispersions is treated in terms of the energy changes which take place when particles approach one another. The theory involves estimations of the energy of attraction (London-van der Walls forces) and the energy of repulsion (overlapping of electric double layers) in terms of inter-oarticle distance. But in addition to electrostatic interaction, steric repulsion has also to be considered. 

The other two forces depicted in Figure 1 are called colloid-chemical forces. London-van der Waals forces (FLvdw) are present between all solids they are usually attractive and are fairly well characterized theoretically and experimentally for several systems. The remaining force arrow in Figure 1, Fchem, represents a collection of chemical forces that may be repulsive or attractive. These chemical forces may arise from electrostatic, steric, and other interactions between particles in water. They are described primarily in the colloid chemical literature. Our ability to express these forces quantitatively and accurately may be written as Fgray = Fdrag > FLVDW > Fchem. 

The main interaction forces acting on colloidal systems are van der Waals attractive forces, and electrostatic and steric repulsive forces [1]. We shall introduce... 

Since the beginning of colloids science, however it is also known that the agglomeration of colloids and dispersed particles can be prevented or controlled by stabilization [8]. The attractive interactions between the colloidal particles, caused by van-der-Waals forces, need to be compensated by repulsive interactions. The latter can be based either on electrostatic repulsion due to same-sign surface charges (electrostatic stabilization), or on repulsion via a polymer shell formed through adsorption of polymers to the particle surface (steric stabilization, in presence of polyelectrolytes termed electrosteric stabilization due to additional charged-induced repulsion) [9, 10]. The stabilization by control of the interaction forces between colloidal particles has been in the focus of extensive research efforts. Already... 

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