Diving into surfaces: the role of surfactants in oil in water emulsions
Event details
| Date | 21.05.2010 |
| Hour | 09:00 |
| Speaker | Sylvie Roke, Max-Planck Institute for Metals Research |
| Location | |
| Category | Conferences - Seminars |
Sum frequency scattering (SFS) spectroscopy offer a unique way of obtaining molecular information (chemical composition, molecular orientation, order and chirality) of the interfaces of micro- and nanoscopic particles in a solution or in a solid matrix. We present vibrational SFS measurements on 80 nm SDS-stabilized hexadecane oil droplets in water, which essentially provide a vibrational spectrum of the oil, the surfactant and the water phase that are present in the mono-molecular thick layer that is the interface. We find that the SDS surfactant does not mix with the oil phase, in contrast to planar oil/water interfaces. The interfacial density of adsorbed SDS is more than one order of magnitude lower than that at a corresponding planar interface. From our data we can derive a maximum decrease in interfacial tension, which turns out to be an order of magnitude lower than on a corresponding planar interface (5 mN/m, instead of 42 mN/m). These first molecular and surface specific measurements paint a picture of surfactant action that is radically different from the commonly accepted role of surfactants and call for a revision of our understanding of soft matter interfaces.
Practical information
- General public
- Free