Polymer adsorption and colloid stability

Polymers will readily adsorb onto the surface of particles or droplets and are commonly used to control the stability and rheology of particulate dispersions and emulsions [9-12]. 

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Ringenbach, E., Chauveteau, G., and Pefferkom, E.. Effect of soluble aluminum ions on polyelectrolyte-alumina interaction. Kinetics of polymer adsorption and colloid stabilization. Colloids Surf. A, 99, 161, 1995. 

Meredith JC, Johnston KP. Theory of polymer adsorption and colloid stabilization in supercritical fluids. 2. Copolymer and end-grafted stabilizers. Macromolecules 1998 31, 5518-5528. 

Tadros, T.F. (1982) Polymer adsorption and colloid stability, in The Effect of Polymers on Dispersion Properties (ed. T.F. Tadros), Academic Press, London. Thompson, W. (Lord Kelvin) (1871)... 

Consider the complexity involved in modeling steric stabilization with a diblock copolymer. The reservoir bulk solution of copolymer is usually dilute (<1 wt % polymer) and the copolymer and solvent equilibrate between the bulk and surface regions. However, as solvent quality is decreased to the LCST phase boundary, the bulk solution will also separate into polymer-rich and polymer-lean phases. In addition, many diblock copolymers form self-assembled aggregates such as micelles and lamellae, if the concentration is above the critical micelle concentration. Thus, stabilizer can partition among up to four phases as solvent quality or polymer concentration is changed. The unique density dependence of supercritical fluids adds another dimension to the complex phase behavior possible. In the theoretical studies discussed below, surfactant adsorption energy, solubility, and concentration are chosen carefully to avoid micelle formation or bulk phase separation, in order to focus primarily on adsorption and colloid stability. 

Adsorption in Colloid and Surface Science - A Universal Concept 175 Polymer adsorption and steric stabilization... 

Figure 7.6 Polymer adsorption and steric stabilization of colloid systems. Adapted from Wesselingb et al. (2007), with permission from John Wiley Sons, Ltd...

Among the various branches in colloid and interface science, polymer adsorption and its effect on the colloid stability is one of the most crucial problems. Polymer molecules are increasingly used as stabilizers in many industrial preparations, where stability is needed at a high dispersed phase volume fraction, at a high electrolyte concentration, as well as under extreme temperature and flow velocity conditions. 

There are very important phenomena originated when a polymer is on one interface or close to one interface. Such phenomena include adsorption, adhesion, monolayer formation, coating and colloidal stabilization. In the majority of circumstances a polymer adsorbed onto colloidal particles will increase the stability of a dispersion [8], The essential feature of polymer or steric stabilization is... 

The use of natural and synthetic polymers to stabilize aqueous colloidal dispersions is technologically important, with much research in this area being focused on adsorption and steric stabilization [286-291]. Steric stabilization is discussed further in the next section. 

Protective agents can act in several ways. They can increase double layer repulsion if they have ionizable groups. The adsorbed layers can lower the effective Hamaker constant. An adsorbed film may necessitate desorption before particles can approach closely enough for van der Waals forces to cause attraction, or approaching particles may simply cause adsorbed molecules to become restricted in their freedom of motion (volume restriction). The use of natural and synthetic polymers to stabilize aqueous colloidal dispersions is technologically important, with research in this area being focused on adsorption and steric stabilization [75-80]. 

Many uses of polymers are concerned with the properties of polymers at interfaces. Chapter 2 presents a summary of theories of polymer adsorption and discusses the properties and state of polymers at interfaces and methods for determining the details of their structure, conformations, and so on. The basic theory of colloid-interaction forces in terms of DL VO theory is presented, together with a discussion of the different basic stabilization mechanisms of colloids. 

G. J. Fleer, Polymer Adsorption and Effect in Colloidal Stability, H. Veenman and Zonen, N.V., Wageningen. 1971. 

Fleer, G. J., and Lyklema, J. 1976. Polymer adsorption and its effect on the stability of hydrophobic colloids. El. Kinetics of the flocculation of silver iodide sols. t.Coll.lnt Sd. 55 228-238. 

Fleer, G.J. and J. Lyklema. 1974. Polymer adsorption and its effect on stability of hydrophobic colloids. 2. Flocculation process as studied with silver iodide polyvinyl alcohol system. Journal of Colloid and Interface Science 46 (1) 1-12. 

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

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... 

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. 

Other applications. Displacement must also have its impact on colloidal stability. The relation between the adsorption of polymers on colloidal particles and the resultant steric stability... 

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... 

Polymer Adsorption at the Lower Critical Solution Temperature and Its Effect on Colloid Stability... 

Adsorption behavior and the effect on colloid stability of water soluble polymers with a lower critical solution temperature(LCST) have been studied using polystyrene latices plus hydroxy propyl cellulose(HPC). Saturated adsorption(As) of HPC depended significantly on the adsorption temperature and the As obtained at the LCST was 1.5 times as large as the value at room temperature. The high As value obtained at the LCST remained for a long time at room temperature, and the dense adsorption layer formed on the latex particles showed strong protective action against salt and temperature. Furthermore, the dense adsorption layer of HPC on silica particles was very effective in the encapsulation process with polystyrene via emulsion polymerization in which the HPC-coated silica particles were used as seed. 

In this study, adsorption behavior of water soluble polymers and their effect on colloid stability have been studied using polystyrene latices plus cellulose derivatives. As the aqueous solution of hydroxy propyl cellulose(HPC) has a lower critical solution temperature(LCST), near 50 °C(6 ), an increased adsorption and strong protection can be expected by treating the latices with HPC at the LCST. 

In the micellar region the trend to decreasing colloid stability is arrested and a partial improvement, in line with the enhanced level of polymer adsorption, is noted until the conditions for gross phase separation are reached. Only the intermediate block copolymer BC 42 shows indications of discontinuities in behavior at the solvent composition for micelle formation. The results presented here do not show the sharp transition from stability to instability found experimentally (4,8,17) by Napper and generally expected on theoretical grounds. However, there are important differences in experimental methodology that must be emphasised. 

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