title: Hydrophobic Hydration in Water-tert-Butyl Alcohol Solutions by Extended Depolarized Light Scattering.
abstract: Molecular dynamics and structural properties of water-tert-butyl alcohol (TBA) mixtures are studied as a function of concentration by extended depolarized light scattering (EDLS) experiments. The wide frequency range, going from fraction to several thousand GHz, explored by EDLS allows distinguishing TBA rotational dynamics from structural relaxation of water and intermolecular vibrational and librational modes of the solution. Contributions to the water relaxation originating from two distinct populations, i.e. hydration and bulk water, are clearly identified. The dynamic retardation factor of hydration water with respect to the bulk, ξ ≈ 4, almost concentration independent, is one of the smallest found by EDLS among a variety of systems of different nature and complexity. This result, together with the small number of water molecules perturbed by the presence of TBA, supports the idea that hydrophobic simple molecules are less effective than hydrophilic and more complex molecules in perturbing the H-bond network of liquid water. At increasing TBA concentrations the average number of perturbed water molecules shows a pronounced decrease and the characteristic frequency of librational motions reduces significantly, both of which are results consistent with the occurrence of self-aggregation of TBA molecules.
authors.affiliation: †IOM-CNR c/o Dipartimento di Fisica e Geologia, Università di Perugia, Via Pascoli, I-06123 Perugia, Italy.|‡Dipartimento di Fisica e Geologia, Università di Perugia, Via Pascoli, I-06123 Perugia, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Comez
authors.affiliation: §Dipartimento di Chimica, Biologia e Biotecnologie, Università di Perugia, Via Elce di Sotto 8, I-06123 Perugia, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Paolantoni
authors.affiliation: ∥Department of Chemistry, The University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112-0850, United States.
authors.forename: L
authors.initials: L
authors.lastname: Lupi
authors.affiliation: §Dipartimento di Chimica, Biologia e Biotecnologie, Università di Perugia, Via Elce di Sotto 8, I-06123 Perugia, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Sassi
authors.affiliation: ‡Dipartimento di Fisica e Geologia, Università di Perugia, Via Pascoli, I-06123 Perugia, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Corezzi
authors.affiliation: §Dipartimento di Chimica, Biologia e Biotecnologie, Università di Perugia, Via Elce di Sotto 8, I-06123 Perugia, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Morresi
authors.affiliation: ‡Dipartimento di Fisica e Geologia, Università di Perugia, Via Pascoli, I-06123 Perugia, Italy.|⊥Centro di Eccellenza sui Materiali Innovativi Nanostrutturati (CEMIN), Università di Perugia, Via Elce di Sotto 8, I-06123 Perugia, Italy.
authors.forename: D
authors.initials: D
authors.lastname: Fioretto
mesh_terms: D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D008027:Light; D056004:Molecular Dynamics Simulation; D012399:Rotation; D012542:Scattering, Radiation; D012996:Solutions / Q000737:chemistry; D012997:Solvents / Q000737:chemistry; D013059:Spectrum Analysis, Raman; D014732:Vibration; D014867:Water / Q000737:chemistry*; D020002:tert-Butyl Alcohol / Q000737:chemistry*
chemical_list: D012996:Solutions; D012997:Solvents; D014867:Water; D020002:tert-Butyl Alcohol