Membrane Formation by Preferential Solvation of Ions in Mixture of Water, 3-Methylpyridine, and Sodium Tetraphenylborate

Published

December 1, 2013

Author(s)

Koichiro Sadakane, Michihiro Nagao, Hitoshi Endo, Hideki Seto

Abstract

The structure and dynamics of a ternary system composed of deuterium oxide (D₂O), 3- methylpyridine (3MP), and sodium tetraphenylborate (NaBPh₄) are investigated by means of small-angle neutron scattering (SANS) and neutron spin echo (NSE). In the SANS experiments, a structural phase transition is confirmed between a disordered-phase and an ordered-lamellar-phase by changing the composition and/or temperature of the mixture. The characteristic length of the structures is on the order of sub-micrometers. A dispersion relation of the structure is measured using NSE, which shows that the relaxation rate follows a momentum transfer cubed relation. This implies that the dynamics of the system is predominantly determined by membrane fluctuations. The present results indicate that 3MP-rich layers are microscopically separated from bulk water in the presence of NaBPh₄, and that the layers behave as membranes. A preferential solvation of salt in each solvent induces a microphase separation between the solvents. An electrostatic interaction between the 3MP-rich layers could be a dominant force for stabilising the long-range periodic structures.

Citation

Journal of Chemical Physics

Volume

139

Issue

23

Pub Type

Journals

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Keywords

membrane, dynamics, structure, 3-methylpyridine, sodium tetraphenylborate

Citation

Sadakane, K. , Nagao, M. , Endo, H. and Seto, H. (2013), Membrane Formation by Preferential Solvation of Ions in Mixture of Water, 3-Methylpyridine, and Sodium Tetraphenylborate, Journal of Chemical Physics, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=908317 (Accessed October 12, 2025)