Berlin 2015 – scientific programme
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DY: Fachverband Dynamik und Statistische Physik
DY 68: Glasses and Glass Transition (joint session CPP/ DF/ DY)
DY 68.4: Talk
Friday, March 20, 2015, 10:15–10:30, C 243
Dynamics of the glass transition in confined glycerol under hard and soft confinement, investigated by 2H NMR — •Michael Lannert, Matthias Sattig, Thomas Blochowicz, and Michael Vogel — Hochschulstraße 6-8, 64289 Darmstadt, Germany
2H NMR allows us to access correlation times of molecular rotational dynamics, ranging from τ=10−12s to τ=10−1s, by using longitudinal relaxation, solid echo, and stimulated echo sequences. Findings for confined glycerol, which is subjected to spherical soft confinement (using AOT/toluene micro-emulsions) and cylindrical hard confinement (using microporous silica, namely MCM-41) are compared, and a shift in correlation times to shorter times is observed for the hard confinement, but not for the soft confinement. Various diameters (2nm to 9nm) were used in order to gain a comprehensive understanding of the finite size effect. Investigation of the dynamics of the glycerol in the supercooled regime proved to be a challenging enterprise in soft confinement, because of the onset of rotational diffusion of the whole microemulsion droplet, which exceeds the contribution of molecular rotational dynamics. Therefore droplet size-dependence and viscosity-dependence of the dynamics where investigated additionally, in order to evaluate the impact of these results.