25-30 August 2019
Henry Ford Building
Europe/Berlin timezone

Velocity auto-correlation spectra of water-glycerol binary fluid

Not scheduled
4h
Harnack House and Henry Ford Building

Harnack House and Henry Ford Building

Board: 305
Poster Posters

Speaker

Prof. Ales Mohoric (University of Ljubljana, Institute Josef Stefan)

Description

The molecular dynamics of water in mixtures with 5−66 vol% of glycerol was studied by measuring the spectrum of the velocity auto-correlation (VAS) in the frequency range from 50 Hz to 10 kHz with the NMR method of modulated gradient spin echo (MGSE). The ability of the method to follow the time evolution of VAS reveals the heterogeneity of molecular dynamics in water and its mixtures with low glycerol content attributed to the diffusion in the vortexes of hydrodynamic fluctuations. By increasing the glycerol content, the spectrum exhibits a low-frequency peak that can be attributed to water clustered around a glycerol molecule. By taking into account the generalized Stokes-Einstein formula the form of VAS exposes the shear-thickening viscosity of mixtures, a possible mechanism behind the spontaneous folding of disordered poly-peptides into biologically active protein molecules. Results show that a low glycerol concentration only partially disrupts the hydrogen network of water and its molecular dynamics, but a higher glycerol completely changes the structure and dynamics in mixtures. In glycerol concentrations equal or higher than 10 vol% a new form of VAS develops, which confirms the existence of hydro-clusters formed around hydrophilic glycerol molecules. This strongly influences the dynamics of surrounding water molecules. Viscosity of such mixture inhibits the rapid movement of water molecules and thus protects the macro-molecule against collisions that would prevent the formation of its own structure.

Primary authors

Prof. Ales Mohoric (University of Ljubljana, Institute Josef Stefan) Janez Stepisnik (University of Ljubljana, Institute Josef Stefan) Carlos Mattea (Ilmenau University of Technology) Siegfried Stapf (Ilmenau University of Technology)

Presentation Materials

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