USE OF PENDENT DROP TECHNIQUE AS A FILM BALANCE AT LIQUID-LIQUID INTERFACES

The pendent drop technique has been extended to investigate insoluble monolayers of the phospholipid dipalmitoylphosphatidylcholine at the w ater/n-dodecane interface. The change of the drop size enables one to compress and expand the surfactant film. The dynamic interfacial tensi on of the film obtained by using axisymmetric drop shape analysis (ADS A) as a function of surface area provides thermodynamic data of the mo nolayer. The isotherm obtained with ADSA shows the same type of dynami c behaviour as measured with the classic Langmuir-Blodgett trough tech nique, Dynamic behaviour of insoluble monolayers, such as monofilm rel axation can be studied by ADSA more readily than by the common Langmui r film balances because of the uniform temperature of the entire syste m and uniform interfacial pressure and concentration along the drop su rface.