Effect of alkyl functionalization on charging of colloidal silica in apolar media

Mobility of black pigments for electrophoretic display depending on the characteristics of carbon sphere

“…In this study, the effect of SPAN 80, a type of Sorb, on the changes in the electrophoretic mobility of polymer covered carbon spheres was examined in tetrachloroethylene as a non-polar solvent. The increasing surface charge of silica particle with SPAN species regardless of surface acidity has already be described by Poovarodom S. et al, and it is ascribed to the acidic nature of SPAN species [32]. Similar to the results in silica particles, the zeta potential of the polymerized carbon sphere was increased, regardless of the properties of the as-synthesized particles.…”

Surfactants with colloids: Adsorption or absorption?

“…Different surfactants have been used to disperse silica nanoparticles, depending on the nature of the solvent and the particle surface chemistry [15]. Several groups have recently studied charges of silica nanoparticles dispersed in alkanes in the presence of AOT [37][38][39][40][41], but only very small concentrations of silica can be dispersed due to the lack of Coulombic attraction between AOT anions and the negatively charged silica surfaces. Alumina nanoparticles can also be charged in alkanes in the presence of AOT [40].…”

Controlling colloid charge in nonpolar liquids with surfactants

“…These other studies do not examine such a wide range of concentrations, although they both reach a maximum concentration of 10 mM where, as can be seen in Figure 5, charge reversal should have occurred. 47,73 Silica surfaces treated with, for example, cyano, amine, or hydroxyl surfaces have been observed to be charged, although the sign of the charge depends on the surfactant and the surface functionalization. Cyano-treated silica with AOT surfactant has been observed to be negatively charged, 124 as has amino-treated silica in the presence of either PIBS or Span surfactants.…”

“…61 For studies which examine the concentration dependence over a wide range, five or six orders of magnitude to include samples both with and without inverse micelles present, the value of ζ or µ is found to increase to a maximum, around 1 mM, when it either plateaus (in the case of ζ ) or begins to decrease (in the case of µ). 47,67,120,123 There have been fewer studies into charging hydrophobic surfaces with surfactants other than AOT, and the results do not agree as clearly. Span 85 surfactant was found to induce a positive charge on PMMA in hexane using PALS, except for low concentrations and high applied fields where the sign reverses.…”

“…34,47 There are conflicting results for the charging behavior of Zr(Oct) 2 . It has been found to charge particles both negatively 47 and positively. 66,77 Given that these studies are on three different hydrophobic surfaces (PMMA, hydrophobically-modified silica, and carbon black),…”