Dresden 2011 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 38: Poster: Colloids and Complex Liquids
CPP 38.11: Poster
Wednesday, March 16, 2011, 17:00–19:00, P2
Water in Reverse Micelles Studied by Neutron Scattering — •Tinka Spehr1, Bernhard Frick2, Isabelle Grillo2, and Bernd Stühn1 — 1Institut für Festkörperphysik, TU Darmstadt — 2Institut Laue-Langevin, Grenoble, France
We performed neutron scattering studies on water-in-oil droplet microemulsions based on the anionic surfactant AOT to investigate the effect of micelle size on the dynamics of water. First we studied the structure and the self dynamics of the droplets as a function of temperature and composition. Using small-angle neutron scattering and elastic scans on neutron backscattering (BS) we characterized the microemulsion structure and its stability. We find that the droplets are stable down to temperatures where the contained water is deeply supercooled [1],[2]. Neutron-spin-echo was then used to determine the bending elasticity of the surfactant film and the diffusion coefficient of the entire droplets in the oil matrix [2]. Finally we focussed on the water dynamics inside droplets of two different sizes, ω = 3 (8) corresponding to R = 7 (12) Å, combining neutron time-of-flight and BS. The average mobility of the confined water is slowed down compared to bulk water. Inside bigger droplets we observed two dynamically separated water fractions - probably corresponding to bound shell water and bulk-like core water - whereas in smaller droplets all water appears to be closely bound [3]. Wide-angle X-ray scattering is used to monitor ice formation inside the droplets. [1] T. Spehr et al., Phys. Rev. E 79 (2009), 031404; [2] T. Spehr et al., J. Phys.: Condens. Matter 20 (2008), 104204; [3] T. Spehr, PhD Thesis, TU Darmstadt (2010)