Self-diffusion of glycerol in γ-alumina nanopores. The neglected role of pore saturation in the dynamics of confined polyalcohols

Gerardo Campos-Villalobos, Flor R. Siperstein, Carmine D'Agostino, Luke Forster, Alessandro Patti

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Abstract

We report on Molecular Dynamics simulations and Pulse-Field Gradient (PFG)-NMR experiments to investigate the dynamics of glycerol in γ-Al2O3 nanopores and shed light on the controversial observations on the behavior of viscous fluids under confinement. While our simulation results confirm the role played by the solid in determining the hydrogen-bond network at the interface with the liquid and hence its mobility, they additionally disclose an intriguing scenario where this mobility is remarkably influenced by a vapor–liquid interface that is present in pores that are not fully saturated as also suggested by our (PFG)-NMR measurements. This interface significantly reduces the number of inter-molecular hydrogen bonds in glycerol and sparks a faster dynamics than that measured in the bulk liquid. Consequently, the surprising enhancement of glycerol's self-diffusion in γ-Al2O3 nanopores can be explained only if both degree of confinement and pore saturation are taken into consideration. Our results suggest that the discrepancies reported in the literature are most likely due to measurements performed in pores that are not completely filled with glycerol.

Original languageEnglish
Article number146089
JournalApplied Surface Science
Volume516
Early online date18 Mar 2020
DOIs
Publication statusPublished - 30 Jun 2020

Keywords

  • Diffusion
  • Molecular dynamics simulations
  • Nanoporous materials
  • Viscous liquids

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