Temperature-Dependent Phase Behavior, Particle Size, and Conductivity of Middle-Phase Microemulsions Stabilized by Ethoxylated Nonionic Surfactants

The present paper deals with the influence of salinity and temperature on the phase behavior and conductivity of middle-phase microemulsions stabilized by ethoxylated nonionic surfactants. Optimal salinity of microemulsion increases with increases in temperature. Middle phase microemulsion shows stability for temperatures up to 330 K, and then the relative phase volume of middle phase decreases slightly. Particle size distribution of the rnicroemulsion formulations with different ethoxylated nonionic surfactants have been studied by dynamic light scattering. Percolation behavior of the middle-phase microemulsion systems have been studied as a function of mass fraction of water for different nonionic surfactants at 0.02 mass fractions of NaCl concentration by electrical conductivity measurement. The temperature effect on the electrical conductivity of middle-phase microemulsions is also studied. With an increase in temperature, the conductivity increases and the activation energy of the system also increases with an increase in ethylene oxide number of the nonionic surfactants.