Structure and conductivity of AOT solutions in n‐hexadecane‐chloroform mixtures

Abstract

The structure and conductivity of AOT (sodium bis(2-ethylhexyl) sulfosuccinate) solutions (2.5 × 10 −4-2.5 × 10 −1 M) in n-hexadecane-chloroform mixture at the chloroform concentration from 50 to 100 vol% were studied. The diffusion ordered spectroscopy NMR study revealed that in the indicated range, the observed hydrodynamic diameter of micelles depends only on the AOT concentration and does not depend on the chloroform content. Molar fractions of free AOT molecules and those aggregated into micelles were calculated using the Lindman's law: at concentrations above 2.5 × 10 −1 М, the solutions contain mostly the micelles, whereas at concentrations below 2.5 × 10 −4 M, the solutions contain AOT molecules. The transition region contains both the AOT molecules and the micelles. Conductivity measurements were used to determine free charge carriers in the bulk of solutions and their contributions to conductivity.

Electrophoretic mobility and stability of SiO2 nanoparticles in the solutions of AOT in n‐hexadecane‐chloroform mixtures

“…Establishment of the nature of carriers and determination of the concentration of free charges in the solutions of AOT in n ‐hexadecane‐chloroform mixture, carried out in our previous work [19], allowed us to calculate the electrokinetic potential of SiO 2 from electrophoretic mobility and to estimate (within DLVO theory) the stability of dispersions and the possibility of the formation of electrostatically bound aggregates with oppositely charged silver and gold nanoparticles. The obtained results are qualitatively confirmed by experiments.…”

“…In this connection, initial recharge of the surface in the case of small AOT concentration may be explained by the overequivalent adsorption of AOTNa 2+ ions on the hydrophilic surface of SiO 2 . Then sorption does not change, and a decrease in the electrokinetic potential is due to a decrease in the diffuse part of the EDL as a result of an increase in the ionic strength of the solution with an increase in AOT concentration [19].…”

“…()–(). The numerical values for κ –1 parameter for all AOT solutions were obtained in our previous work [19].…”

“…In Ref. [19], we reported a detailed study of the structure and electrical conductivity of the solutions of AOT (2.5 × 10 –4 ÷2.5 × 10 –1 mol/L) in n ‐hexadecane–chloroform mixture within chloroform concentration range from 50 to 100 vol.%. By means of DOSY‐NMR (diffusion ordered spectroscopy nuclear magnetic resonance), we determined the carriers of free charge in bulk solutions (ionized molecules and micelles of AOT) and their contributions into electrical conductivity.…”