Electrostatic effects in films stabilised by non-ionic surfactants

The disjoining pressure Π of films of aqueous octyl-β-glucoside (β-C8G1) solutions with and without salt was measured as a function of the film thickness by means of a thin film pressure balance. The analysis of the experiments confirms the presence of an electrostatic double layer which dominates the long-range interactions as found in previous experiments with other non-ionic surfactants in the presence of added salt. In the absence of salt, we find a local ion concentration much higher than that of the residual ionic impurities present in the bulk solution.

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