Yoshiki Ishii1,2, Nobuyuki Matubayasi3,2, Go Watanabe4, Takashi Kato5, Hitoshi Washizu1,2. 1. Graduate School of Information Science, University of Hyogo, 7-1-28 Minatojima-Minamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan. y.ishii@sim.u-hyogo.ac.jp kato@chiral.t.u-tokyo.ac.jp h@washizu.org. 2. Elements Strategy Initiative for Catalysts and Batteries, Kyoto University, Katsura, Kyoto 615-8520, Japan. 3. Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan. 4. Department of Physics, School of Science, Kitasato University, Sagamihara, Kanagawa 252-0373, Japan. 5. Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan. y.ishii@sim.u-hyogo.ac.jp kato@chiral.t.u-tokyo.ac.jp h@washizu.org.
Abstract
Self-assembled ionic liquid crystals can transport water and ions via the periodic nanochannels, and these materials are promising candidates as water treatment membranes. Molecular insights on the water transport process are, however, less investigated because of computational difficulties of ionic soft matters and the self-assembly. Here we report specific behavior of water molecules in the nanochannels by using the self-consistent modeling combining density functional theory and molecular dynamics and the large-scale molecular dynamics calculation. The simulations clearly provide the one-dimensional (1D) and 3D-interconnected nanochannels of self-assembled columnar and bicontinuous structures, respectively, with the precise mesoscale order observed by x-ray diffraction measurement. Water molecules are then confined inside the nanochannels with the formation of hydrogen bonding network. The quantitative analyses of free energetics and anisotropic diffusivity reveal that, the mesoscale geometry of 1D nanodomain profits the nature of water transport via advantages of dissolution and diffusion mechanisms inside the ionic nanochannels.
Self-assembled ionic liquid crystals can transport water and ions via the periodic nanochannels, and these materials are promising candidates as water treatment membranes. Molecular insights on the water transport process are, however, less investigated because of computational difficulties of ionic soft matters and the self-assembly. Here we report specific behavior of water molecules in the nanochannels by using the self-consistent modeling combining density functional theory and molecular dynamics and the large-scale molecular dynamics calculation. The simulations clearly provide the one-dimensional (1D) and 3D-interconnected nanochannels of self-assembled columnar and bicontinuous structures, respectively, with the precise mesoscale order observed by x-ray diffraction measurement. Water molecules are then confined inside the nanochannels with the formation of hydrogen bonding network. The quantitative analyses of free energetics and anisotropic diffusivity reveal that, the mesoscale geometry of 1D nanodomain profits the nature of water transport via advantages of dissolution and diffusion mechanisms inside the ionic nanochannels.