SURFACE LIGHT-SCATTERING STUDIES OF DIPALMITOYLPHOSPHATIDYLCHOLINE MONOLAYERS AT THE AIR WATER AND HEPTANE WATER INTERFACES

Spread films of dipalmitoylphosphatidylcholine (DPPC) at the air/0. 01 M NaCl (A/W) and heptane/0. 01 M NaCl (O/W) interfaces were studied at 25 degree C by the technique of surface quasi-elastic light scattering (SLS) from interfacial capillary waves and the static Wilhelmy plate method. The dynamic surface longitudinal elasticity and the viscosity were determined by analyzing the SLS spectra at A/ W. The dynamic elasticity was found to be different from the static elasticity in both the vapor/liquid-expanded and liquid-expanded/ liquid-condensed biphasic regions. Thedynamic and static longitudinal elasticities were similar in the liquid-expanded region. This study is motivated by an interest in the tendency of phospholipids to spontaneously self-assemble in water to form bilayered structures siilar to biological membranes.