塩の選択溶媒和によって誘起されるメゾスケールの液体構造

抄録

The effect of an antagonistic salt, NaBPh₄, on a mixture of D₂O / 3-methylpyridine (3MP) is investigated by visual observation, optical microscopy, small-angle neutron scattering (SANS) and neutron spin echo (NSE). In the case that the amount of NaBPh₄ is smaller than 15 mM, the mixture colors in near-critical region. With increasing the amount of salt, the phase separation disappears and a single peak profile is observed at finite-Q by SANS. Furthermore, a structural phase transition between a disordered-phase and an ordered-lamellar-phase are confirmed in D₂O-rich region. The characteristic length of those structures is sub-micrometers. In this condition, a dispersion relation of these structures was measured using NSE, which showed a momentum transfer cubed relation. This result implies that the dynamics of the system might be predominantly determined by membrane fluctuations. The present results indicate that the 3MP domains are microscopically separated from water and the domains behaves as membranes. A preferential solvation to each solvent can induce the microphase separation between the solvents.