Publisher DOI: 10.1063/5.0040705
arXiv ID: 2012.14664v3
Title: Dynamics of Water Confined in Mesopores with Variable Surface Interaction
Language: English
Authors: Jani, Aicha 
Busch, Mark  
Mietner, J. Benedikt 
Ollivier, Jacques 
Appel, Markus 
Frick, Bernhard 
Zanotti, Jean-Marc 
Ghoufi, Aziz 
Huber, Patrick  
Fröba, Michael 
Morineau, Denis 
Keywords: Physics - Chemical Physics
Issue Date: 7-Mar-2021
Source: The journal of chemical physics 154 (9): 094505 (2021-03-07)
Abstract (english): 
We have investigated the dynamics of liquid water confined in mesostructured porous silica (MCM-41) and periodic mesoporous organosilicas (PMOs) by incoherent quasielastic neutron scattering experiments. The effect of tuning the water/surface interaction from hydrophilic to more hydrophobic on the water mobility, while keeping the pore size in the range 3.5-4.1 nm, was assessed from the comparative study of three PMOs comprising different organic bridging units and the purely siliceous MCM-41 case. An extended dynamical range was achieved by combining time-of-flight (IN5B) and backscattering (IN16B) quasielastic neutron spectrometers providing complementary energy resolutions. Liquid water was studied at regularly spaced temperatures ranging from 300 K to 243 K. In all systems, the molecular dynamics could be described consistently by the combination of two independent motions resulting from fast local motion around the average molecule position and the confined translational jump diffusion of its center of mass. All the molecules performed local relaxations, whereas the translational motion of a fraction of molecules was frozen on the experimental timescale. This study provides a comprehensive microscopic view on the dynamics of liquid water confined in mesopores, with distinct surface chemistries, in terms of non-mobile/mobile fraction, self-diffusion coefficient, residence time, confining radius, local relaxation time, and their temperature dependence. Importantly, it demonstrates that the strength of the water/surface interaction determines the long-time tail of the dynamics, which we attributed to the translational diffusion of interfacial molecules, while the water dynamics in the pore center is barely affected by the interface hydrophilicity.
ISSN: 0021-9606
Journal: The journal of chemical physics 
Institute: Center for Integrated Multiscale Material Systems M-2 
Document Type: Article
Project: Veränderung der Eigenschaften mehrphasiger Flüssigkeiten durch geometrische Beschränkung in modernen mesoporösen Materialien 
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