Stability of colloids

The repulsion between two double layers is important in determining the stability of colloidal particles against coagulation and in setting the thickness of a soap film (see Section VI-5B). The situation for two planar surfaces, separated by a distance 2d, is illustrated in Fig. V-4, where two versus x curves are shown along with the actual potential. 

J. L. Moilliet, B. Collie, and W. Black, Surface Activity, E. F. N. Spon, London, 1961. D. H. Napper, Polymeric Stabilization of Colloidal Dispersions, Academic, New York,... 

Mapper D H 1983 Polymeric Stabilization of Colloidal Dispersions (London Academic)... 

Stabilization of Colloidal Dispersions by Polymer Adsorption, Tatsuo Sato and Richard Ruch... 

D. H. Napper, Polymeric Stabilization of Colloidal Dispersion, Academic Press, New York (1983). 

Napper DH (1983) Polymeric stabilization of colloidal dispersions. Academic, New York... 

FIGURE 8.45 The stability of colloids is illustrated by this violet liquid, which is a colloid of metallic gold that has survived since it was prepared by Michael Faraday in 1857... 

The process of adsorption of polyelectrolytes on solid surfaces has been intensively studied because of its importance in technology, including steric stabilization of colloid particles [3,4]. This process has attracted increasing attention because of the recently developed, sophisticated use of polyelectrolyte adsorption alternate layer-by-layer adsorption [7] and stabilization of surfactant monolayers at the air-water interface [26], Surface forces measurement has been performed to study the adsorption process of a negatively charged polymer, poly(styrene sulfonate) (PSS), on a cationic monolayer of fluorocarbon ammonium amphiphilic 1 (Fig. 7) [27],... 

T Sato, R Ruch. Stabilization of Colloidal Dispersions by Polymer Adsorption (Surfactant Science Series, No. 9). New York Marcel Dekker, 1980, pp 65-119. 

The stability of colloids can also be dramatically altered by inclusion of polymeric materials. If the polymer interacts favourably with the particle surfaces, i.e. it adsorbs, then both an increase and a reduction in stability is possible, via modification of the electrostatic interaction of the polymer is charged or a reduction in the van der Waals attraction. 

At short interparticle distances, the van der Walls forces show that two metallic particles will be mutually attracted. In the absence of repulsive forces opposed to the van der Walls forces the colloidal metal particles will aggregate. Consequently, the use of a protective agent able to induce a repulsive force opposed to the van der Walls forces is necessary to provide stable nanoparticles in solution. The general stabihzation mechanisms of colloidal materials have been described in Derjaguin-Landau-Verway-Overbeck (DLVO) theory. [40,41] Stabilization of colloids is usually discussed... 

Emulsions and Emulsion Technology (in three parts), edited by Kenneth J. Lissant Anionic Surfactants (in two parts), edited by Warner M. Linfieid see Volume 56) Anionic Surfactants Chemical Analysis, edited by John Cross Stabilization of Colloidal Dispersions by Polymer Adsorption, Tatsuo Sato and Richard Ruch... 

Zeichner, G. R., and Schowalter, W. R., Use of trajectory analysis to study stability of colloidal dispersions in flow fields. AIChE J. 23, 243-254 (1977). 

Finally, we have designed and synthesized a series of block copolymer surfactants for C02 applications. It was anticipated that these materials would self-assemble in a C02 continuous phase to form micelles with a C02-phobic core and a C02-philic corona. For example, fluorocarbon-hydrocarbon block copolymers of PFOA and PS were synthesized utilizing controlled free radical methods [104]. Small angle neutron scattering studies have demonstrated that block copolymers of this type do indeed self-assemble in solution to form multimolecular micelles [117]. Figure 5 depicts a schematic representation of the micelles formed by these amphiphilic diblock copolymers in C02. Another block copolymer which has proven useful in the stabilization of colloidal particles is the siloxane based stabilizer PS-fr-PDMS [118,119]. Chemical... 

Adsorption of polyelectrolyte on interfaces is concerned with various applications such as flocculation and steric-stabilization of colloidal particles in an aqueous phase, oil recovery, and soil conditioning. In these cases, both the adsorbance of polyelectrolytes and the conformation of the adsorbed polymer, which is connected with the thickness of the adsorbed layer, are very important. 

Polymer adsorption is important in the flocculation and stabilization of colloidal sols and has been reviewed by Vincent et al. (1) and Tadros (2). Polyvinyl alcohol (PVA) has been used in these studies because of its practical application in textiles, adhesives, and coatings. The adsorption of PVA has been studied on silver iodide by Fleer (3) and Koopal (4), and on polystyrene (PS) latex particles by Garvey (5). The adsorption isotherms reported by these workers extend up to 600 ppm PVA. The adsorption at... 

In recent years much attention has been paid to the stability of colloids in the presence of free, nonadsorbing polymers. It is generally found that at relatively low polymer concentrations... 

In studying the stability of colloidal dispersions it is of considerable advantage if the particles concerned are monodisperse and spherical. For aqueous, charge-stabilised systems polymer latices have proved invaluable in this regard. With non-aqueous systems, steric stabilisation is usually required. In this case it... 

Sato, T. Ruch, R., Stabilization of Colloidal Dispersion by Polymer Adsorption, Marcel Dekker, Inc., NY, 1980. 

Heurtault B, Saulnier P, Pech B, et al. Physico-chemical stability of colloidal lipid particles. Biomaterials 2003 24(23) 4283. 

The stability of colloidal systems is subject to the state of their configuration, very roughly comparable to a bucket that is stable when standing up but if tilted beyond a certain angle, topples and comes to rest on its side (Figure 7.1). 

The stability of colloid suspensions is an important criteria in the manufacture of a large number of industrial products where these are the basic building blocks (food colloids, pollution control, emulsions, wastewater treatment). 

---