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article i nfo Experiments with foam films from solutions of 1 mM SDS+100 mM electrolyte (LiCl, NaCl and CsCl) were carried out by a thin-film-pressure balance. The measured dependences of disjoining pressure versus film thickness exhibit a steep increase when the thickness of the film's water core becomes smaller than 3.7 nm. This behavior can be interpreted as a manifestation of the hydration force. We unsuccessfully tried to interpret the data with different available theoretical models. Eventually, we found that a relatively simple model of "reduced screening" can fit the data. Such reduced screening of the electric field could exist only in a narrow range of film thicknesses, which practically coincides with the region where the hydration repulsion is acting. This model and its experimental verification are described in the article. |
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