Electrical Properties of Polyelectrolyte Layers Adsorbed on Colloidal Particles at Different Ionic Strength

Abstract

The investigation presents results on the low-frequency electrical polarization of β-FeOOH particles with adsorbed layers from sodium salts of poly(4-styrene sulfonate), poly(acrylic acid), and carboxymethyl cellulose, obtained by electric light scattering. The adsorption is realized in aqueous NaCl solutions of different concentration, and the suspensions of the coated particles are then rinsed to low conductivity. Several electro-optical parameters are sensitive to the conformation of the adsorbed polyelectrolyte layer. The particle electrical polarizability increases drastically with the concentration of NaCl (correlating with significant increase of the adsorbed amount of polyelectrolyte), while their electrophoretic mobility remains practically unchanged. Two time scales are involved in the stepwise relaxation of the electrical polarizability. The faster process is attributed to movement of ions in the polymer layer, restricted by the coiled conformation to smaller distances. The contribution of the Debye atmosphere outside the polymer layer remains almost unchanged, which correlates with the low sensitivity of the electrophoretic mobility to the increasing amount of adsorbed polyelectrolyte. Abrupt increase in a narrow interval of salt concentrations is observed both for the low-frequency component of the particle polarization and for the hydrodynamic layer thickness, indicating changes in the surface electric state, most probably due to swelling of the adsorbed polymer layer.

Complexation of Ferric Oxide Particles with Pectins of Ordered and Random Distribution of Charged Units

“…The small difference in effective charge density of both pectin samples seems to explain reasonably the similar electro-optical effects at low field strengths. We attribute the increase in the electro-optical effect from the less charged pectin to the movement of ions in the polymer matrix, restricted by the more coiled conformation of the adsorbed chains to smaller distances as compared with the pectin with random distribution of charged units . In agreement with this interpretation is the small increase in the relaxation frequency of the electro-optical effect from the particles coated with the less charged pectin (inset in Figure ).…”

Smart and green interfaces: From single bubbles/drops to industrial environmental and biomedical applications

“…Significant changes in the conformation and electrical properties of the adsorbed polyelectrolyte chains were demonstrated in dependence on ionic strength in the solutions of oppositely charged polyelectrolytes [1]. Effect of ionic strength and molecular weight on the stability of adsorbed polyelectrolyte bi-layers was also demonstrated for oxide particles in stabilized suspensions [2].…”

Effect of Organic Matter on the Flocculation of Colloidal Montmorillonite: A Modeling Approach

“…Also at higher salinity, polymer molecules may become more hydrophobic because of the further reduction in polarity (Kumar, 2000), which would diminish repulsive hydration (Israelachvili and Pashley, 1983). Meanwhile, at higher salinity, polymer molecules may be more readily adsorbed onto mineral surfaces (Milkova et al, 2010), potentially increasing the non-DLVO interactions that are lacking in bare montmorillonite systems (e.g., polymer bridging as well as steric forces attributable to polymer chains). It is difficult to fully deconvolute the effect of these various interaction energies on the sticking efficiency and floc-breakup potential.…”