title: Clustering dynamics in water/methanol mixtures: a nuclear magnetic resonance study at 205 k<T<295 k.
abstract: Proton nuclear magnetic resonance (1H NMR) experiments have been performed to measure the spin-lattice, T1, and spin-spin, T2, relaxation times of the three functional groups in water/methanol mixtures at different methanol molar fractions (XMeOH=0, 0.04, 0.1, 0.24, 0.5, 1) as a function of temperature in the range 205 K<T<295 K. The measured relaxation times in the mixtures, at all the methanol molar fractions, are faster than those of pure water and methanol because of strong interactions, resulting in a complex hydrogen bonding dynamics that determines their thermodynamic properties. In particular, we observe how the interplay between hydrophobicity and hydrophilicity changes with temperature and influences the peculiar thermal behavior of the NMR relaxation times of the solution. The obtained results are interpreted in terms of the existence of stable water-methanol clusters at high temperature whereas, upon cooling to low temperature, clusters of single species are present in the mixture.
authors.affiliation: Dipartimento di Fisica and CNISM, Università di Messina, Messina, Italy. ccorsaro@unime.it
authors.forename: Carmelo
authors.initials: C
authors.lastname: Corsaro
authors.forename: Jeroen
authors.initials: J
authors.lastname: Spooren
authors.forename: Caterina
authors.initials: C
authors.lastname: Branca
authors.forename: Nancy
authors.initials: N
authors.lastname: Leone
authors.forename: Matteo
authors.initials: M
authors.lastname: Broccio
authors.forename: Chansoo
authors.initials: C
authors.lastname: Kim
authors.forename: Sow-Hsin
authors.initials: SH
authors.lastname: Chen
authors.forename: H Eugene
authors.initials: HE
authors.lastname: Stanley
authors.forename: Francesco
authors.initials: F
authors.lastname: Mallamace
mesh_terms: D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D009682:Magnetic Resonance Spectroscopy; D000432:Methanol / Q000737:chemistry*; D013696:Temperature; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
chemical_list: D014867:Water; D000432:Methanol