Physicochemical studies on microemulsions .5. Additive effects on the performance of scaling equations and activation energy for percolation of conductance of water/AOT/heptane microemulsion

Both water-induced and temperature-induced percolation of water/AOT/heptane water-in-oil microemulsion have been studied in detail in the presence of a good number of additives alone and in combination. The additives have shown both assisting and resisting effects on the process. The hydroxy bile salts distinctly fall in the former category while tetraethyl ammonium iodide, benzene, toluene, napthalene, xylene, and cholesterol constitute the latter. The nonpercolating system water/AOT/xylene can be made percolating by the addition of 0.5 mol dm(-3) sodium cholate, The scaling laws for both kinds of percolation have been found to be obeyed but the equation parameters differ in magnitude from what theory predicts. The additives have a distinct contribution in this regard, The activation energy required for the percolation process has been determined; the values realized in different additive environments do not follow a general trend. (C) 1996 Academic Press, Inc.