STRUCTURAL FORCES IN THIN-FILMS MADE FROM POLYELECTROLYTE SOLUTIONS

We have studied thin liquid films made from semidilute polyelectrolyte solutions. The disjoining pressure (due to interaction between film s urfaces) has been measured as a function of the film thickness. Pie ob serve pressure oscillations, corresponding to film stratification. The oscillations become sharper as the polymer concentration c increases, and disappear when salt is added. The period of the oscillations scal es as c(-1/2). We propose that the observed stratification is related to the polymer network and the size of the steps to the mesh size xi.