Berlin 2015 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 61: Poster - Glasses

DY 61.3: Poster

Thursday, March 19, 2015, 16:00–18:00, Poster A

Effects of Confinement on the Dynamics of Aqueous Mixtures — •Matthias Sattig and Michael Vogel — Institut für Festkörperphysik, TU Darmstadt, Hochschulstraße 6, 64289 Darmstadt

The dynamical behavior of aqueous mixtures in bulk and in confinement is a topic of great interest. For example, a water concentration dependent behavior of the glass transition temperature was found in PG-water and in PGME-water mixtures, which is very different for the two cases [1]. This was attributed to different possibilities of both molecules to form H-bonds in the bulk and different mechanisms of H-bonding in the presence of additional water. The forming of H-bonds can be disturbed by introducing a geometrical confinement, whose surface interacts with the guest molecules and spatially restricts the bond network. We present rotational correlation times τ of both above mentioned mixtures in bulk and in mesoporous silica MCM-41 at several water concentrations, obtained from ²H-NMR. In the high temperature regime spin-lattice-relaxation experiments show similar results for both mixtures in bulk and in confinement. At lower temperatures they hint at the occurrence of a phase separation, assisting the interpretation from Elamin et al. [2]. They propose the idea of water clustering at the surface. Our results are compared with results from dielectric spectroscopy of the mixtures in bulk and confinement. Similarities with water confined in MCM-41 are discussed, where the observable relaxation at low temperatures was attributed to surface layer of water[3].

[1] Sjöström et al., PCCP, 12, 10452, 2010 [2]; Elamin et al., to be published; [3] Sattig et al., PCCP,16, 19229 , 2014