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



Koichiro Sadakane, Michihiro Nagao, Hitoshi Endo, Hideki Seto


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.
Journal of Chemical Physics


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


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], (Accessed April 20, 2024)
Created November 30, 2013, Updated October 12, 2021