Charge transport in percolated water-in-oil microemulsions

Charge transport studies in percolated water-in-oil microemulsions near the percolation limit have been carried out. We have investigated in particula r CmE5/water/oil systems where either sodium chloride or the surface-active electrolyte AOT were added as carrier electrolytes. We find a markedly dif ferent behavior regarding these electrolytes, which is interpreted quantita tively by the different chemical environment of C12E5 imbedding the AOT mol ecules. Charge transport may be visualized to occur in both systems through droplet/droplet contacts in the interconnected network of chains of nanodr oplets. In the systems containing NaCl as carrier electrolyte, the conducti vity is found to be proportional to the NaCl concentration, as expected for strong electrolytes. The systems containing AOT as carrier electrolyte, on the other hand, show a strongly nonlinear dependence on concentration. A q uantitative consideration of dissociation and association equilibria of AOT yields a dissociation constant of 6 x 10(-4), which conforms to typical we ak electrolytes such as, e.g., formic acid.