Résumé
Conductivity of water in oil microemulsions as well as reverse micelles of anionic surfactants depends on cations as charge transporters. We first use the versatile molecular system toluene/diethylhexylphosphate HxNa1-xDEHP/water to investigate the domains in the phase prism in which four molecular mechanisms of conductivity are identified. The reduced molar conductivity varies over six orders of magnitude. In the regime of "reverse micelles" where all water in the organic phase is bound as the first layer of hydration of head-groups, the dismutation mechanism, discovered by HF Eicke, dominates. In the w/o microemulsion regime, we identify three more conductivity regimes occurring in different regions of the phase diagram. Beyond the dynamic and static percolation, we also identify a more elusive regime: this curvature << frustration >> regime is characterized by a decrease in molar conductivity observed upon the addition of water. This anti-percolation regime is due to curved film packing frustration producing an increase of tortuosity. The HDEHP/toluene/water system is the first molecular system for which all four conductivity regimes can be observed at room temperature in different regions of the phase diagram. We also identify the last three conductivity regimes in a microemulsion based on AOT. The single-phase inversion channel, studied as a function of temperature, is limited by Winsor II and Winsor I phase separation. In this domain, the three regimes that can be found are dynamic percolation, anti-percolation as well as static percolation. Therefore, we propose that all four different mechanisms can always be found in ternary w/o microemulsions containing cations as charge carriers.