Regensburg 2016 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 51: Glasses (joint session CPP/DY, organized by DY)
CPP 51.5: Vortrag
Donnerstag, 10. März 2016, 10:45–11:00, H48
Influence of MCM-41 on the dynamical and phase behaviors of aqueous mixtures — •Matthias Sattig and Michael Vogel — Institut für Festkörperphysik, TU Darmstadt, Hochschulstraße 6, 64289 Darmstadt, Germany
The dynamics of aqueous mixtures in bulk and confinement is a topic of great interest. Two model systems, which exhibit rather different behavior upon varring water concentration are propylene glycol- and propylene glycol monomethyl ether-mixtures. This was attributed to the different ability of both alcohols to form hydrogen bonds in neat systems and in aqueous mixtures. The formation of H-bond networks can be altered by geometrical confinement, whose surface interacts with the guest molecules and provides spatially restriction. Here we provide temperature dependent deuteron-NMR data of heavy water in mixture with PG, PGME or di-PGME confined in mesoporous MCM-41 in a broad dynamic range. We examin the rotational autocorrelation using stimulated echo experiments and spin-lattice-relaxation. The latter exhibits a typical minimum in its relaxation time T1, below which several relaxation processes could be identified in the different mixtures, supporting the idea of a phase separation in confinement, that was proposed in QENS [1] and dielectric [2] investigations. We compare our results with the dynamics of water [3] and glycerol confined in the same material to discuss similarities and differences relating to the influence of confinement on the dynamics of neat and mixed systems. [1] Swenson et al., JCP, 141, 214501, 2014 [2] Elamin et al., PCCP, 17, 12978, 2015 [3] Sattig et al., JCPL, 5, 174 - 178 , 2014