Polymerizable Photocleavable Columnar Liquid Crystals for Nanoporous Water Treatment Membranes

Abstract

Here, we describe a strategy to obtain nanoporous liquid-crystalline (LC) membranes by incorporating a photocleavable ortho-nitrobenzyl group in polymerizable columnar liquid crystals. Two derivatives were synthesized with propylene and nonylene spacers, respectively, between the ionic and the photocleavable moieties to introduce various size nanopores after photocleavage. The membranes were prepared by photopolymerization in the LC states, followed by photocleavage and washing with methanol. The resulting membranes show a virus rejection of 99.99%. Although the rejection value remained almost the same for the two membranes, water flux increased with increasing the length of the alkyl spacers. These membranes were found to be almost free from pinhole defects. The present study offers a new methodology for the development of nanoporous membranes with organized nanostructures for separation technologies.

Transport mechanisms of water molecules and ions in sub-nano channels of nanostructured water treatment liquid-crystalline membranes: a molecular dynamics simulation study

“…However, these films contain a disordered structure and the nanopores or sub-nanopores formed in those membranes for the transportation of water molecules and ions are not uniform. [3][4][5][6][7][8][9][10][11][12] Hence, materials that contain nanopores or sub-nanopores with uniform sizes, such as carbon nanotubes (CNTs) [13][14][15][16][17][18][19][20] and polymerized liquid crystals, [21][22][23][24][25][26][27][28][29] have attracted a great deal of interest as candidates for efficient water treatment membranes. It is expected that the alignment of pores, which is required for high water permeability, will be easier for polymerized liquid crystals than for CNTs.…”

Liquid Crystal‐Based Water Treatment Membranes

“…By combining a photocleavable ortho-nitrobenzyl moiety in acrylic acid-based polymerizable columnar liquid crystals, Gupta et al [85] prepared the nanoporous liquid-crystalline membranes. To achieve different sized nanopores after photocleavage, authors synthesized the two derivatives with propylene (16) and nonylene (17) spacers, between the photocleavable and ionic moieties (Figure 15A).…”

“…[86] Copyright 2019, American Chemical Society. [85] to introduce photocleavable moieties in nanostructured polymerizable liquid crystals to obtain nanoporous membranes. Reproduced with permission.…”

High Virus Removal by Self‐Organized Nanostructured 2D Liquid‐Crystalline Smectic Membranes for Water Treatment

“…[8][9][10][11][12][13] In the conventional method to prepare membranes, it is difficult to obtain regular sized pores and pinhole free surface. Advanced water filtration membranes have been proposed with materials such as liquid crystals, [14][15][16][17][18][19][20] carbon nanotubes, [21][22][23][24][25][26] and block polymers. [27][28][29][30][31] Some of these materials showed high virus removal.…”

“…[32] Liquid crystals have been shown for constructing functional membranes. [33][34][35][36][37][38][39] Liquid crystals can form LC nanostructures such as smectic, [39] columnar [18][19][20]35,37,38] and bicontinuous cubic phases. [17,18,36] Recently, we found the polymerized bicontinuous cubic (Cub bi ) [17] and tetragonal columnar (Col t ) [19] liquid crystals for fabricating efficient virus removal membrane.…”