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Title: Quasielastic neutron scattering studies on glass-forming ionic liquids with imidazolium cations

Relaxation processes for imidazolium-based ionic liquids (ILs) were investigated by means of an incoherent quasielastic neutron scattering technique. In order to clarify the cation and anion effects on the relaxation processes, ten samples were measured. For all of the samples, we found three relaxations at around 1 ps, 10 ps, and 100 ps-10 ns, each corresponding to the alkyl reorientation, the relaxation related to the imidazolium ring, and the ionic diffusion. The activation energy (E{sub a}) for the alkyl relaxation is insensitive to both anion and alkyl chain lengths. On the other hand, for the imidazolium relaxation and the ionic diffusion processes, E{sub a} increases as the anion size decreases but is almost independent of the alkyl chain length. This indicates that the ionic diffusion and imidazolium relaxation are governed by the Coulombic interaction between the core parts of the cations (imidazolium ring) and the anions. This is consistent with the fact that the imidazolium-based ILs have nanometer scale structures consisting of ionic and neutral (alkyl chain) domains. It is also found that there is a clear correlation between the ionic diffusion and viscosity, indicating that the ionic diffusion is mainly associated with the glass transition which is one ofmore » the characteristics of imidazolium-based ILs.« less
Authors:
; ; ;  [1] ;  [2] ;  [3]
  1. Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan)
  2. NIST Center for Neutron Research, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899-6102 (United States)
  3. (United States)
Publication Date:
OSTI Identifier:
22493350
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 143; Journal Issue: 23; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ACTIVATION ENERGY; ANIONS; CATIONS; CORRELATIONS; DIFFUSION; GLASS; IMIDAZOLES; MOLTEN SALTS; NEUTRON DIFFRACTION; QUASI-ELASTIC SCATTERING; RELAXATION; VISCOSITY