Influence of Anionic Surfactants on the Electric Percolation of AOT/Isooctane/Water Microemulsions

Luis García-Río, Juan C. Mejuto, Moisés Pérez-Lorenzo, Antonio Rodríguez-Álvarez, and Pedro Rodríguez-Dafonte
Langmuir, 2005, 21, 6259–6264


A study was carried out concerning the influence of sodium alkyl sulfonates on the electric percolation of AOT/isooctane/water microemulsions ([AOT] = 0.5 M and W = [H2O]/[AOT] = 22.2). An important effect was observed with regard to the percolation temperature caused by the addition of small quantities of alkyl sulfonates (ρ = [alkyl sulfonate]/[AOT] = 0.01). The short chain alkyl sulfonates (C3−C5) cause an increase in the percolation temperature, which in turn is reduced as we increase the chain length of the additive until we obtain a percolation temperature which is lower than that which is observed in the absence of an additive (C6−C8). For hydrocarbon chains of a greater length we can observe a new increase in the percolation temperature (C10−C18). This behavior has been explained as a consequence of (i) the incorporation of the additives at the interphase of the microemulsion and (ii) the geometric parameters of the different surfactants added to the microemulsion.