Interactive forces on Aerosol-OT/n-hexane/water/urea reversed micelles by small angle x-ray scattering

The influence of urea on Aerosol-OT (AOT)/n-hexane/water reversed micelles (RMs) at molar concentration ratio [water]/[AOT]=10 is investigated by mean s of small angle x-ray scattering. The data are analyzed within the framewo rk of repulsion and attractive interaction potentials through the sticky ha rd-sphere model. In the absence of urea the simple hard sphere (excluded vo lume) model applies up to RM volume fraction phi of 0.32. In the presence o f 5M urea, the x-ray curves evidence a big influence of the attractive forc es in the system for phi=0.06, in good agreement with previous light scatte ring results, without disturbing the RM structure (shape and size). When ph i exceeds this value, a percolation phenomenon is observed by ionic conduct ance measurements. In addition, the data show an interplay between attracti ve and repulsive RM interactions at higher phi values, with preservation of the discrete RM structure, without the formation of a "long-lived" biconti nuous phase. (C) 1999 American Institute of Physics.