SURFACE-LAYERS OVERLAP AND EFFECTIVE ADHESION IN REVERSE MICELLES - ADISCUSSION FROM THE ADHESIVE SPHERES MIXTURE MODEL

Structural data on reverse micelles from the literature are analyzed f rom the adhesive spheres mixture model in the Percus-Yevick approximat ion. The solvent is modeled by a fluid of pseudoadhesive spheres with same compressibility and coordination number as a square well fluid. T he attractive part of the direct intermicellar potential is taken prop ortional to the overlap volume of interpenetrating surface layers. The micelle-solvent coupling is characterized by a square or triangular w ell and a constraint on the packing fractions. A very good correlation is then found between the micelles stickiness parameters computed fro m the actual potentials via the equality of second virial coefficients and those determined from a fit to experiment. The change in effectiv e adhesion observed with micelles of different surface composition and in the same solvent can then be associated to the change in the direc t intermicellar interaction at nearly unchanged solvent-micelle intera ctions. The interpretation of the role of tho overlap volume resulting from this multicomponent approach is contrasted with that based on ap proximate calculations of the potential of mean force. (C) 1997 Americ an Institute of Physics.