FORMATION OF HIGHLY CONDENSED FERRIC STEARATE MONOLAYERS AT THE AIR-WATER-INTERFACE

Pressure-molecular area isotherms of a Langmuir monolayer of preformed ferric stearate on water have been studied at various temperatures, c ompression rates, and pH values. The isotherms indicate anomalously sm all areas per molecule for the ferric stearate monolayers. A probable model is put forward to explain the small molecular areas. This model retains the area per hydrocarbon chain to 18 Angstrom observed in othe r similar systems, with a head-to-tail ratio of 1:3, but assigns a dom inant role to hydrophobic forces in forming and stabilizing the monola yer. The X-ray reflectivity profile calculated from this model matches well with the measured data of deposited Langmuir-Blodgett film of fe rric stearate.