Supply of safety water is one of the most important issues for the public health and life. Polymer membranes for water treatment are essential materials for water supply. New membrane materials are required to desalinate seawater and remove harmful substances with higher efficiency. Our idea is to develop new separation membranes for water treatment from liquid crystals that self-organize to form nano-channel structures with controlled pore size and functional groups.
2-1) Selective Transportation through Liquid-Crystalline Sub-Nano- and Nano-Channels and Examination of the Mechanisms
We have developed nano-structured polymer membranes by fixation of the liquid-crystalline (LC) structures. The fan-shaped molecules having ammonium and imidazolium moieties form bicontinuous structures with three-dimensional nano-channels and columnar structures with one-dimensional channels. Polymer membranes based-on these nanochannels show salt removal properties, unique ion removal selectivity, and high virus removal properties. These characters of the membranes are due to their ordered nano-channel structures and the defect-less surfaces because of the fluidity of the monomers. The struture-property relationships of the sub-nanopores in the membranes have been examined by molecular dynamics simulations and synchrotron-based X-ray emission spectroscopy. These studies revealed that hydrogen-bonding structures of water molecules in the nanochannels affects the ion permeability of the channels.
2-2) Efficient Virus Filtration
We found that our LC nanostructured polymer membranes show excellent virus stopping properties (>99.99% - >99.9999%) even though against small viruses such as bacteriophage Qβ (diameter 25 nm). Controlled pore-size enlargement of the LC nanochannels by using two-components systems and photocleavage reactions of columnar LC channels enhanced water-permeability of the membranes. In addition, two-dimensional channels prepared from rod-shaped molecules and H-shaped molecules forming smectic phases enabled much increased water flux and higher virus rejection. Especially, the bilayer smectic structures give higher water permeation compared to the monolayer smectic molecules.
Selected papers on this subject:
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Aquatic Functional Liquid Crystals: Design, Functionalization, and Molecular Simulation
T. Kato, J. Uchida, Y. Ishii, and G. Watanabe
Adv. Sci., 11, 2306529 (2024). Open Access -
Hydrogen-Bonded Structures of Water Molecules in Hydroxy-Functionalized Nanochannels of Columnar Liquid Crystalline Nanostructured Membranes Studied by Soft X-ray Emission Spectroscopy
K. Hamaguchi, T. Sakamoto, N. Kurahashi, Y. Harada, and T. Kato
J. Phys. Chem. Lett., 15, 454-460 (2024). Open Access -
Development of Liquid-Crystalline Smectic Nanoporous Membranes for the Removal of SARS-CoV-2 and Waterborne Viruses
T. Sakamoto, K. Asakura, N. Kang, R. Kato, M. Liu, T. Hayashi, H. Katayama, and T. Kato
J. Mater. Chem. A, 11, 22178-22186 (2023). Open Access -
Removal of Viruses from Their Cocktail Solution by Liquid-Crystalline Water-Treatment Membranes
D. Kuo, T. Sakamoto, S. Torii, M. Liu, H. Katayama, and T. Kato
Polym. J., 54, 821-825 (2022). - Molecular Insights on Confined Water in the Nanochannels of Self-Assembled Ionic Liquid Crystal
Y. Ishii, N. Matubayasi, G. Watanabe, T. Kato, and H. Washizu
Sci. Adv., 7, eabf0669 (2021). Open Access -
Gemini Thermotropic Smectic Liquid Crystals for Two-Dimensional Nanostructured Water-Treatment Membranes
K. Hamaguchi, R. Ichikawa, S. Kajiyama, S. Torii, Y. Hayashi, J. Kumaki, H. Katayama, and T. Kato
ACS Appl. Mater. Interfaces, 13, 20598-20605 (2021). -
Ion Selectivity of Water Molecules in Subnanoporous Liquid-Crystalline Water-Treatment Membranes: A Structural Study of Hydrogen Bonding
R. Watanabe, T. Sakamoto, K. Yamazoe, J. Miyawaki, T. Kato, and Y. Harada
Angew. Chem. Int. Ed., 59, 23461-23465 (2020). Open Access -
Development of Functional Nanoporous Membranes Based on Photocleavable Columnar Liquid Crystals - Selective Adsorption of Ionic Dyes
Y. Suzuki, T. Sakamoto, M. Yoshio, and T. Kato
Eur. Polym. J., 134, 109859-1/7 (2020). -
High Virus Removal by Self‐Organized Nanostructured 2D Liquid‐Crystalline Smectic Membranes for Water Treatment
D. Kuo, M. Liu, K. R. S. Kumar, K. Hamaguchi, K. P. Gan, T. Sakamoto, T. Ogawa, R. Kato, N. Miyamoto, H. Nada, M. Kimura, M. Henmi, H. Katayama, and T. Kato
Small, 16, 202001721-1/5 (2020). -
Transport Mechanisms of Water Molecules and Ions in Sub-nano Channels of Nanostructured Water Treatment Liquid-Crystalline Membranes: A Molecular Dynamics Simulation Study
H. Nada, T. Sakamoto, M. Henmi, T. Ogawa, M. Kimura, and T. Kato
Environ. Sci.: Water Res. Technol., 6, 604-611 (2020).. -
Polymerizable Photocleavable Columnar Liquid Crystals for Nanoporous Water Treatment Membranes
M. Gupta, Y. Suzuki, T. Sakamoto, M. Yoshio, S. Torii, H. Katayama, and T. Kato
ACS Macro Lett., 8, 1303-1308 (2019). -
Nanostructured Virus Filtration Membranes Based on Two-Component Columnar Liquid Crystals
K. Hamaguchi, D. Kuo, M. Liu, T. Sakamoto, M. Yoshio, H. Katayama, and T. Kato
ACS Macro Lett., 8, 24-30 (2019). -
Development of Nanostructured Water Treatment Membranes Based on Thermotropic Liquid Crystals: Molecular Design of Sub-Nanoporous Materials
T. Sakamoto, T. Ogawa, H. Nada, K. Nakatsuji, M. Mitani, B. Soberats, K. Kawata, M. Yoshio, H. Tomioka, T. Sasaki, M. Kimura, M. Henmi, and T. Kato
Adv. Sci., 5, 1700405 (2018). Open Access
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Highly Efficient Virus Rejection with Self-Organized Membranes Based on a Crosslinked Bicontinuous Cubic Liquid Crystal
N. Marets, D. Kuo, J. R. Torrey, T. Sakamoto, M. Henmi, H. Katayama and T. Kato
Adv. Healthcare Mater., 6, 1700252(2017). -
Self-Organized Liquid-Crystalline Nanostructured Membranes for Water Treatment: Selective Permeation of Ions
M. Henmi, K. Nakatsuji, T. Ichikawa, H. Tomioka, T. Sakamoto, M. Yoshio,T. Kato
Adv. Mater ., 24, 2238 (2012).