title: Dynamics of water-alcohol mixtures: insights from nuclear magnetic resonance, broadband dielectric spectroscopy, and triplet solvation dynamics.
abstract: We combine (2)H nuclear magnetic resonance (NMR), broadband dielectric spectroscopy (BDS), and triplet solvation dynamics (TSD) to investigate molecular dynamics in glass-forming mixtures of water and propylene glycol in very broad time and temperature ranges. All methods yield consistent results for the α process of the studied mixtures, which hardly depends on the composition and shows Vogel-Fulcher temperature dependence as well as Cole-Davidson spectral shape. The good agreement between BDS and TDS data reveals that preferential solvation of dye molecules in microheterogeneous mixtures does not play an important role. Below the glass transition temperature T(g), NMR and BDS studies reveal that the β process of the mixtures shows correlation times, which depend on the water concentration, but exhibit a common temperature dependence, obeying an Arrhenius law with an activation energy of E(a) = 0.54 eV, as previously reported for mixtures of water with various molecular species. Detailed comparison of NMR and BDS correlation functions for the β process unravels that the former decay faster and more stretched than the latter. Moreover, the present NMR data imply that propylene glycol participates in the β process and, hence, it is not a pure water process, and that the mechanism for molecular dynamics underlying the β process differs in mixtures of water with small and large molecules.
authors.affiliation: Institut für Festkörperphysik, Technische Universität Darmstadt, Hochschulstraße 6, 64289 Darmstadt, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Sauer
authors.affiliation: Institut für Festkörperphysik, Technische Universität Darmstadt, Hochschulstraße 6, 64289 Darmstadt, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Schuster
authors.affiliation: Institut für Festkörperphysik, Technische Universität Darmstadt, Hochschulstraße 6, 64289 Darmstadt, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Rosenstihl
authors.affiliation: Institut für Festkörperphysik, Technische Universität Darmstadt, Hochschulstraße 6, 64289 Darmstadt, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Schneider
authors.affiliation: Institut für Angewandte Physik, Technische Universität Darmstadt, Schlossgartenstraße 7, 64289 Darmstadt, Germany.
authors.forename: V
authors.initials: V
authors.lastname: Talluto
authors.affiliation: Institut für Angewandte Physik, Technische Universität Darmstadt, Schlossgartenstraße 7, 64289 Darmstadt, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Walther
authors.affiliation: Institut für Festkörperphysik, Technische Universität Darmstadt, Hochschulstraße 6, 64289 Darmstadt, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Blochowicz
authors.affiliation: Institut für Festkörperphysik, Technische Universität Darmstadt, Hochschulstraße 6, 64289 Darmstadt, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Stühn
authors.affiliation: Institut für Festkörperphysik, Technische Universität Darmstadt, Hochschulstraße 6, 64289 Darmstadt, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Vogel
mesh_terms: D000438:Alcohols / Q000737:chemistry*; D058266:Dielectric Spectroscopy; D009682:Magnetic Resonance Spectroscopy; D012995:Solubility; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
chemical_list: D000438:Alcohols; D014867:Water