Correlation Between Maximum Water/Electrolyte Solubilizat1on and Conductivity Percolation in Aot Reversed Micelles

Water/electrolyte solubilization measurements have been performed in order to investigate the conditions in which AOT reversed micelles in decane (or dodecane) can coexist with an external water-phase (the so-called Winsor II systems). The efficacy of different monovalent (Na+, K+) and divalent (Ca2+, Ba2+) salts have been compared putting a special emphasis on the case of the tetramethylammonium lon (TMA+), which is known to have only weak interactions with charged sites. Whatever the cation, the maxima for water/electrolyte solubilization correlates very well with a dramatic change of conductivity. An explanation based on the possible existence of a critical value of the Debye screening length is proposed to account for the fact that a minor change in salt concentration around these maxima can drastically change the surfactant film behavior.