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SUMMARY:Diving into surfaces: the role of surfactants in oil in water emul
 sions
DTSTART:20100521T090000
DTSTAMP:20260916T043955Z
UID:1181967ba39dbc3e18b141ad2d625286e77a711c9a0b75d02260c35f
CATEGORIES:Conferences - Seminars
DESCRIPTION:Sylvie Roke\, Max-Planck Institute for Metals Research\nSum fr
 equency scattering (SFS) spectroscopy offer a unique way of obtaining mole
 cular information (chemical composition\, molecular orientation\, order an
 d chirality) of the interfaces of micro- and nanoscopic particles in a sol
 ution or in a solid matrix. We present vibrational SFS measurements on 80 
 nm SDS-stabilized hexadecane oil droplets in water\, which essentially pro
 vide a vibrational spectrum of the oil\, the surfactant and the water phas
 e 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 con
 trast 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 inter
 facial 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 fir
 st molecular and surface specific measurements paint a picture of surfacta
 nt action that is radically different from the commonly accepted role of s
 urfactants and call for a revision of our understanding of soft matter int
 erfaces. 
LOCATION:BM 5202 https://plan.epfl.ch/?room==BM%205202
STATUS:CONFIRMED
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