Comparison between Interaction Forces at Air/Liquid and Solid/Liquid Interfaces in the Presence of Non-Ionic Surfactants

Interactions in thin liquid foam films and between solid/liquid surfaces coated with the non-ionic surfactant hexaoxyethylene dodecylether (C12E6) were investigated with a TFPB (thin film pressure balance) and the MASIF (Measurement and Analysis of Surface Interaction Forces) technique, respectively. For foam films the formation of common black films (CBF) and Newton black films (NBF) was observed depending on the surfactant concentration and the applied pressure. With increasing surfactant concentration and increasing pressure the CBF is destabilized, whereas a stabilization of the NBF is observed. In addition, MASIF measurements with two different hydrophobic surfaces were made. In one case silanated glass surfaces and in the other case thiolated gold surfaces were used. Differences and similarities of the interactions between these two surfaces are shown and discussed. Furthermore, the results of the MASIF measurements are compared with the ones of the thin film pressure balance measurements and the influence of the surfactant concentration on the interactions is discussed.