Salt Effects in Free Nonionic Films

The thickness has been measured of macroscopic aqueous films, stabilized by nonionic surfactants consisting of a hydrophobic part and a poly(ethy1ene oxide) moiety. Special attention has been paid to the influence of electrolytes. In the fiis, the surfactants behave like coiled polymers. Addition of electrolytes increases the rate of drainage. As a function of the electrolyte concentration, the equilibrium thickness passes through a maximum. These maxima are similar to those for the Huggins constant for the corresponding micelles