Investigation On Conductivity Behavior Of AOT Reverse Microemulsion

Microemulsion that consist of surfactants, cosurfactant, oil and water at a certain percentage is a thermodynamic stable system with the particle radius of 10~200nm. Its interfacial tension is very low. Alkanol is often used directly as a solvent or reaction medium, thus it was important to study the behavior of the surfactant in the alcohol oil. The conductivity behaviors of water-in-toluene-alkanol (heptanol,decanol) reverse microemulsions stabilized by AOT with and without the additives (sodium chloride, sodium salicylate and sodium cholate) were investigated by the conductance measurements. The effect of temperature on the conductance were also studied. This paper also studied the effect of different alkanol and nonionic surfactant (Brij-56, TX-100, Tween80, Spans) on conductance behavior of water /AOT/IPM/alkanol systems, and the droplets size were measured through dynamic light scattering (DLS). The results are as follows:1. The percolation phenomenon was apparently resisted by toluene in the water/AOT/decanol system, while no effect in the water/AOT/heptanol system. The different effects of additives on the conductivity behavior were observed and discussed. The conductance of water/AOT/heptanol/toulene system had a hardly change in the present of sodium chloride and sodium salicylate, and it decreased with the increase of sodium cholate concentration. The conductance of water/AOT/decanol/toulene system increased with the increase of sodium cholate and sodium salicylate concentration, and it changed a little with the concentration of sodium chloride. No percolation threshold induced by temperature was detected either in the absence or in the presence of additives in the 5~40°C.2. There were different effect of alcohol (ethanol, propanol, butanol, pentanol) on the conductane of water/AOT/IPM/alkanol systems. The results showed that the presence of alcohol significantly increased the conductivity. The ethanol, propanol and butanol assisted the percolation, whereas no percolation phenomenon was observed in water /AOT/IPM/pentanol system. The influence of additives (NaCl, NaSal and NaC) on the conductivity of water /AOT/IPM/butanol system were different. 3. Nonionic surfactant (Brij-56, TX-100 and Tween80) decreased the percolation threshold of water /AOT/IPM/butanol system, namely assisting percolation; while the conductivity decreased with the increasing concentration of Spans surfactant, and little impact was found on the percolation.4. The droplets size of the water/AOT/IPM, water/AO/IPM/propanol(butanol) and water/AOT/IPM/Brij-56(TX-100)/butanol system were measured through dynamic lights cattering (DLS). The results showed that the droplets size became large with the increase of water content, and diffusion coefficient decrease. The droplet size became much smaller with the increasing the alcohol concentration. Compared to AOT reverse microemulsion, the addition of Brij-56(TX-100) made droplet size larger and diffusion coefficient smaller at percolation occurs.