Water in Mesoporous Confinement: Glass-To-Liquid Transition or Freezing of Molecular Reorientation Dynamics?

The first mechanical relaxation measurements (f = 400 Hz) of water confined in micro-porous silica were performed more than 40 years ago. The authors reported a so called "capillary transition" (here denoted as P3) of water in the core of the pores and a second one at a lower temperature,...

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Bibliographic Details
Published in:Molecules (Basel, Switzerland) Switzerland), 2019-10, Vol.24 (19), p.3563
Main Authors: Schranz, Wilfried, Soprunyuk, Viktor
Format: Article
Language:English
Subjects:
Adsorbates
Crystal defects
Crystallization
Freezing
Glass transition
mesoporous silica
Molecular Dynamics Simulation
NMR
Nuclear magnetic resonance
Phase transitions
Pore size
Pores
Porosity
Silica
Silicon Dioxide - chemistry
supercooled confined water
Temperature
Thermodynamics
Vitrification
Water - chemistry
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Summary:The first mechanical relaxation measurements (f = 400 Hz) of water confined in micro-porous silica were performed more than 40 years ago. The authors reported a so called "capillary transition" (here denoted as P3) of water in the core of the pores and a second one at a lower temperature, which they called the "adsorbate transition" (P1 in present work) related to water near the surface of the pores. The capillary transition was identified with the freezing of water in the centre of the pores. However, even 40 years later, the origin of the adsorbate transition is not yet clear. One study relates it to the liquid-to-glass transition of the supercooled water in the pores, and another study to the freezing of the proton reorientations at the lattice defects. The present work shows the data from extensive dynamic mechanical analysis (DMA) measurements (f = 0.1 Hz-70 Hz) of water confined in mesoporous silica (d = 2.5, 5 and 10 nm), which are in favour of a liquid-to-glass scenario.
ISSN:1420-3049
1420-3049
DOI:10.3390/molecules24193563