The varying states of water confined in the nano-domain structures of typical room temperature ionic liquids (ILs) were investigated by 1H NMR and by measurements of self-diffusion coefficients while systematically varying the IL cations and anions. The NMR peaks for water in BF4-based ILs were clearly split, indicating the presence of two discrete states of confined water (H2O and HOD). Proton and/or deuterium exchange rate among the water molecules was very slowly in the water-pocket. Notably, no significant changes were observed in the chemical shifts of the ILs. Self-diffusion coefficient results showed that water molecules exhibit a similar degree of mobility, although their diffusion rate is one order of magnitude faster than that of the IL cations and anions. These findings provide information on a completely new type of confinement, that of liquid water in soft matter.

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Non-crystal formation of ice is investigated by simultaneous X-ray diffraction and differential scanning calorimetry measurements upon cooling to -100 °C. At room temperature, size-tunable water confinement (≈20 Å size) in a room-temperature ionic liquid (RTIL, 1-butyl-3-methylimidazolium nitrate, [C4 mim][NO3 ]) exists in a water-rich region (70-90 mol % D2 O). The confined water (water pocket) is characterized by almost monodispersive size distribution. In [C4 mim][NO3 ]-x mol % D2 O (70

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