ABSTRACT
It is expected that the electrostatic interaction is diminished by an addition of inorganic small ions. Curve 10 in Fig. 5 is the adsorption isotherm of the equimolar mixture of SDeS and DeTAB at 298.15 K. It evidently sits very low in the r region compared to curve 4 at the same temperature. This clearly shows that the inorganic ions shields the respective opposite charges and then reduces the electrostatic interaction between cationic and anionic surfactant ions. As mentioned above, the maximum adsorption of the DDAB system was about 7.1 f.!mol of double long chain, i.e., 14.2 f.!mol of single long chain, per square meter and thus the multilayer formation was suggested. However, the maximum adsorption of the DeT ADeS system is about 6 f.!mol of single long chain per square meter and then the adsorbed film is a normal monolayer.
