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Fundamentals of Polymer Solutions
Published in E. D. Goddard, K. P. Ananthapadmanabhan, Interactions of Surfactants with Polymers and Proteins, 2018
Charge, both on the polymer and on the surface, is obviously a key determinant of polyelectrolyte adsorption. For surfaces and polymers bearing the same sign of charge, adsorption is inhibited and can be accomplished only if there is another driving force to adsorb (for example, hydrophobic portions of the polymer and surface which can associate). For opposite charges on the polymer and surface, in salt-free water, the adsorption is very strong and the polyelectrolyte would be expected to have an equilibrium configuration where there is an optimal match between polyion and surface charges. This would lead to a chain which lies essentially flat on the surface. The surface density of chains would be close to σ/Ne, where σ is the charge of the bare surface. The kinetics by which this flattening might occur could be very long since, in this case, the individual segment binding is strong; consequently, surface rearrangements could be slow.
Polymer Adsorption at Oxide Surface
Published in Kunio Esumi, Polymer Interfaces and Emulsions, 2020
Polyelectrolyte adsorption depends strongly on electrostatic parameters such as the surface charge and the polymer charge, which can depend on both the pH and the ionic strength [30-32], Figure 6 shows the effect of the addition of salt on the adsorption of quaternized poly(vinylpyridine) (PVP+) at pH 8 onto TiO2 as a function of the concentration of several cations [33]. The addition of monovalent cations causes an increase in the adsorbed amount until a maximum is found around I = 0.2 mol/kg. At still higher /, the adsorption decreases steeply to zero. No influence of the type of monovalent ion is observed. With the addition of MgCl2, only a decrease in the adsorbed amount is observed. Because the principal interactions are electrostatic, a net electrostatic repulsion arises when overcompensation of the surface charge occurs. The addition of salt screens this replusion, which tends to increase the adsorbed amount. The electrostatic attraction between polymer and surface, however, is also weakened, because the cations compete with the polymer for the negative surface sites. As a result, the adsorbed amount is decreased. On the other hand, the amount of PVP+ adsorbed on SiO2 increases monotonically with ionic strength, suggesting that the adsorption of PVP+ results from both electrostatic and nonelectrostatic interactions. The reversibility of the adsorption of polyelectrolytes on oxides has also been investigated by changing experimental conditions [34]. It is found that polyelectrolyte adsorption on oxides is only partially reversible, because of the strong electrostatic interaction with the surface. This interaction is weakened, and thereby the reversibility enhanced by addition of salt.
Predicting the antagonistic effect between albite-anorthite synergy and anhydrite on chemical enhanced oil recovery: effect of inorganic ions and scaling
Published in Journal of Dispersion Science and Technology, 2020
Eric O. Ansah, Ronald Nguele, Yuchi Sugai, Kyuro Sasaki
In the latter case, the silica surface becomes hydrophobic and uncharged when the polyelectrolyte adsorbs first, hence, reducing the driving force of the surfactant adsorption unto the rock surface. Also, since the polyelectrolyte adsorption is not homogeneous, the surfactant can still be adsorbed on the silica making it hydrophilic to favor oil production.[12] Adsorption of polyelectrolytes on oppositely charged solids depends strongly on the electrostatic interaction, so the nature and concentration of the salt in solution and the pH of the solution may affect polyelectrolyte adsorption.[13,14]