Layers steric

In the present paper, calculations are carried out to explain the restabilization followed sometimes by destabilization, as the electrolyte concentration increases, observed by Stenkamp et al. In these calculations, double-layer, steric, and depletion interactions are taken into account. The steric interaction at various electrolyte concentrations is calculated using the scaling theory. The surface density of the polymer chain was evaluated by using the Sechenov equation for the polymer solubility as a function of electrolyte concentration. 

When the radius of the spherical colloidal particles a is much larger than the shortest distance between the surfaces of two colloidal particles, the free energy between two identical spherical particles, due to double-layer, steric, and depletion interactions, can be calculated using the Derjaguin approximation 2... 

Interaction between Particles Containing Adsorbed Nonionic and Polymeric Sur ctant Layers (Steric Stabilisation)... 

As most nanoemulsions are prepared using nonionic and/or polymeric surfactants, it is necessary to consider the interaction forces between droplets containing adsorbed layers (steric stabilisation). As this was described in detail in Chapter 10, only a summary will be given here [15, 16]. 

The interactions between particles that are important in determining a are made up of Lon-don-van der Waals attractive forces (VJ electrical double layer forces (Vp which can be attractive or repulsive in nature bridging forces (Vp, which are always attractive and steric forces (Vj), which arise from the overlap of adsorbed layers. Steric forces can be repulsive or attractive depending on the solubility properties of the adsorbed layer. 

Overlap of electric double layer Steric interaction of adsorbed polymer Bridge force Hydration force Depletion... 

INTERACTION BETWEEN PARTICLES (DROPLETS) CONTAINING ADSORBED POLYMER LAYERS (STERIC STABILIZATION)... 

A thorough analysis [16, 17, 18, 25] of the hydrodynamic volumic fraction ( h) dependence of the viscosity ri) of mono-layer and double-layer sterically stabilized magnetic fluids of high colloidal stability evidenced that this is best described by the theoretical formula obtained by Chow [27] ... 

The surfactant double-layer steric stabilization procedure was used with good results for a large number of polar carrier liquids, in particular to obtain high-magnetization (up to approximately 950 G) samples on a pentanol carrier, as well as medium-magnetization (up to approximately 300 G) water-based magnetic fluids. 

This follows the same principles discussed above, namely electrostatic repulsion produced by overlap of the double layers, steric repulsion due to the presence of strongly adsorbed surfactants or polymers, or a combination of both. 

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