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Title: Membrane formation by preferential solvation of ions in mixture of water, 3-methylpyridine, and sodium tetraphenylborate

The structure and dynamics of a ternary system composed of deuterium oxide (D{sub 2}O), 3-methylpyridine (3MP), and sodium tetraphenylborate (NaBPh{sub 4}) are investigated by means of small-angle neutron scattering (SANS) and neutron spin echo (NSE) techniques. In the SANS experiments, a structural phase transition is confirmed between a disordered-phase and an ordered-lamellar-phase upon variation of the composition and/or temperature of the mixture. The characteristic lengths of the structures is on the sub-micrometer scale. A dispersion relation of the structure is measured through NSE experiments, which shows that the relaxation rate follows a cubic relation with momentum transfer. This implies that the dynamics of the system are determined predominantly by membrane fluctuations. The present results indicate that 3MP-rich domains are microscopically separated from bulk water in the presence of NaBPh{sub 4}, and that the layers behave as membranes. These results are interpreted that preferential solvation of salt in each solvent induces a microphase separation between the solvents, and the periodic structure of 3MP-rich domains is stabilized by the long-range electrostatic interaction arising from Na{sup +} ions in D{sub 2}O-rich domains.
Authors:
 [1] ;  [2] ;  [3] ; ;  [4]
  1. Department of Physics, Ritsumeikan University, Noji-Higashi 1-1-1, Kusatsu 525-8577 (Japan)
  2. NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6102 (United States)
  3. (United States)
  4. KENS and CMRC, Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba 305-0801 (Japan)
Publication Date:
OSTI Identifier:
22253704
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 139; Journal Issue: 23; Other Information: (c) 2013 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; DISPERSION RELATIONS; FLUCTUATIONS; HEAVY WATER; INTERACTIONS; MEMBRANES; MIXTURES; NEUTRON DIFFRACTION; PERIODICITY; SMALL ANGLE SCATTERING; SODIUM IONS; SOLVATION; SOLVENTS; SPIN ECHO