Interactions between water—stable hydrophobic Langmuir—Blodgett monolayers on mica

A Langmuir-Blodgett technique was used for depositing monolayers of dimethyldioctadecylammonium ions on molecularly smooth muscovite mica surfaces. Direct measurements of the interaction between such surfaces were performed with the surface force apparatus of Israelachvili. A long—range attractive force considerably stronger than the expected van der Waals force was observed. Studies on the salt dependence of this force indicate that it does not have an electrostatic origin. Instead the present results support the view that perturbations of the dynamic association of water molecules outside a hydrophobic surface are propagated several nanometers.