MEASUREMENTS OF THE ELASTIC PROPERTIES OF SURFACTANT AND LIPID MONOLAYERS

The surface forces apparatus technique was used to study the elastic properties of amphiphilic monolayers and bilayers on solid surfaces of mica. Both single-chained and double-chained surfactants (or lipids) were used, and two techniques were used in their preparation: controlled Langmuir-Blodgett deposition and spontaneous self-assembly (adsorption from solution). Our aim was to measure the thickness and compressibility properties of these films and to study how different methods of preparation (e.g., surfactant density) affect these properties. The compressibilities of adsorbed monolayers are in the range (0.5-2) x 10(8) N/m2, which is about an order of magnitude higher than those of the bulk materials, but are similar to the values of free lipid bilayer membranes in aqueous solutions.