Luigi Ambrosone

Analysis of velocity cross-correlation and preferential solvation for the system N-methylpyrrolidone–water at 20 °C

Viscosity, density, diffusion and self-diffusion data have been collected on the system N-methylpyrrolidone–water at 20 °C over the entire composition range. From density and vapour pressure data, affinities, Gαβ(α,β= 1, 2), were computed and compared with the velocity cross-correlation coefficients, fαβ. Good agreement was found between the interpretation of dynamic, fαβ, and thermodynamic, Gαβ, data. Both data are in favour of preferential solute–solvent interactions leading to short-lived hydration aggregates.

Empirical correlations between thermodynamic and spectroscopic properties of aqueous solutions of alkan-m,n-diols. Excess enthalpies and spin–lattice relaxation times at 298.15 K

Enthalpies of dilution in water and nuclear relaxation times at 298.15 K have been determined for binary aqueous solutions containing alkan-α,ω-diols and for ternary aqueous solutions containing the probe molecule hexane-1,2- or hexane-1,6-diol and one of the members of the homologous series of alkane-1,2-diols and of alkane-α,ω-diols, up to heptane-1,7-diol. The results were interpreted through the model of preferential orientation, i.e. the ‘side-on’ model, already proposed to explain the interactions in solution between various positional isomers of hydroxylated substances. For binary solutions, a correlation is presented between the relaxation times and the enthalpic self-interaction coefficients.

Dynamic properties of aqueous solutions of ethylene glycol oligomers as measured by the pulsed gradient spin-echo NMR technique at 25[deg ]C

Self-diffusion coefficients for binary systems containing water and an oligomer of ethylene glycol [HO–(CH2CH2–O)nH, n=1–5], have been measured at 25°C in the whole concentration range by the pulsed gradient spin-echo NMR technique. Upon adding oligomer to pure water, both the oligomer and water self-diffusion coefficients decrease until a certain composition is reached, after which they remain approximately constant. This evidence is interpreted in terms of molecular interactions, especially hydrogen-bond formation. A relation between mutual and self-diffusion coefficients for these systems is found and commented upon.

A self-diffusion study of poly(ethylene-oxide) alkyl alcohols

The self-diffusion coefficients of HDO and some surfactants in aqueous mixtures at different concentrations, below the critical micelle concentration, have been determined by means of the NMR, spin-echo pulsed field gradient method. The surfactant solutes chosen were ethylene glycol-pentyl alcohol (diethylene glycolpentylalcohol, ethylene glycol-hexyalcohol, diethylene glycol-hexyl alcohol, triethylene glycol-hexyl alcohol, tetraethylene glycol-hexyl alcohol, pentaethylene glycol-hexyl alcohol). The interactions in solution are studied by analyzing the solute self-diffusion coefficients extrapolated to infinite dilution. These values are compared with those of 1-alkanols. The slope of the self diffusion coefficientsvs. the solute concentration are correlated with the microscopic friction coefficients. A model for interpreting the experimental data is suggested.

Density and viscosity studies of poly(ethylene-oxide) alkyl alcohols

AbstractDensity and viscosity of binary systems water-nonionic surfactants poly(ethylen-oxide) alkyl alcohols type, [CnH2n+1(OCH2CH2)mOH, CnEm], have been studied. The partial molar volumes in the dilute solution range and the viscosity B-coefficients were calculated. The nonionic surfactants partial molar volumes were compared with those of ethylene glycol and poly(ethylenglycol) (PEG). The comparison shows that the ethoxy unit volume,

Volumetric properties of aqueous solutions of ethylene glycol oligomers at 25 °C

\bar V^O

Free diffusion data in some polymer-solvent systems at 20°C

(OCH2CH2), seems to be independent of the particular system. The consequences of this are discussed. A model for interpreting the experimental B values has been proposed. The model treats the macroscopic viscosity as the superimposition of different local effects. The following surfactants have been considered: C5E1, C5E2, C6E1, C6E2, C6E3, C6E4.

Thermodynamic and Dynamic Properties of Micellar Aggregates of Nonionic Surfactants with Short Hydrophobic Tails

Abstract Through the fluorimetric determination of the critical micellar concentration of dodecylpentaoxyethyleneglycol ether and sodium dodecylsulfate, we have investigated the interaction of the zwitterionic tryptophan and its uncharged analogue N-acetyl- l -tryptophanamide with micelles in terms of binding constants. This could be useful to monitor protein interaction with different membrane-like environments using the intrinsic tryptophan fluorescence. The weakest interaction took place between tryptophan and sodium dodecylsulfate, while the strongest one occurred between N-acetyl- l -tryptophanamide and dodecylpentaoxyethyleneglycol ether. This suggests that micelle head groups control the interaction, but the polar moiety bringing the fluorophore also seems to play a role. The unexpected lack of interaction between tryptophan and dodecylpentaoxyethyleneglycol ether is also discussed.