Interaction of hydrophobic ions with amphiphile monolayers at the air-water interface .1. Monolayers of stearylamine and dioctadecyldimethylammonium

The interaction of monolayers of stearylamine (SAM) and dioctadecyldimethylammonium (DODA) at the air-water interface with hydrophobic ions in the water phase was investigated by using the techniques of two-dimensional pressure isotherms and the surface electrostatic potential. In both cases the interaction with tetraphenylborate anions results in the formation of mixed monolayers whose properties sharply differ from those of the original monolayers. The effect of subphase composition on the formation of mixed monolayers has been studied. A qualitative description of the interaction under study has been given. A model including the phase inhomogeneity of the mixed monolayer and the formation of multilayer structures from the areas of the ''surface salt'' has been suggested. The strong effect of hydrophobic ions on the monolayers is not only due to Coulomb interaction; their hydrophobic properties also play an important role.