Gemini Thermotropic Smectic Liquid Crystals for Two-Dimensional Nanostructured Water-Treatment Membranes

Abstract

We have developed a two-dimensional (2D) liquidcrystalline (LC) nanostructured water-treatment membrane showing high virus rejection ability (over 99.99997% for bacteriophage Qβ) and improved water permeation. Polymerizable gemini amphiphiles have been designed and synthesized. They have H-shaped gemini-type structures of thermotropic smectic liquid crystals composed of cationic imidazolium moieties. One of the gemini amphiphiles shows a smectic A phase with an interdigitated bilayer structure. A cross-linked self-standing 2D nanostructured polymer film has been obtained by in situ photopolymerization of the gemini amphiphile in the smectic phase. The length of linkers in gemini amphiphiles affects the formation of LC phases. The 2D nanostructured membrane also showed selective salt rejection.

Ionic liquid crystals based on amino acids and gemini surfactants: tunable phase structure, circularly polarized luminescence and emission color

“…Actually, the mesogenic property of gemini surfactants is largely dependent on the structural degree of freedom originating from the flexibility and length of their spacer group. 50,51 A longer alkyl spacer may boost the flexibility of the complex, thus generating a disturbance in well-packed ILC nanostructures.…”

“…Gemini surfactants generally feature abundant thermotropic behavior at the thermal annealing. 48–50 Their double chains provide sufficient molecular flexibility to suppress crystallization, and their spacer group as a unique component segment affects the phase structure and transition temperature of ILC. 51 Consequently, gemini surfactants are deemed to be favorable candidates to make up the flexible parts in CPL-active ILCs.…”

Removal of viruses from their cocktail solution by liquid-crystalline water-treatment membranes

“…The diameters of nanopores in the ionic nanochannels in the membranes of 1 and 2 were estimated to be 0.6 nm [ 14 , 25 ], which is much smaller than the diameter of the viruses, which have a diameter of approximately 25–30 nm. The width of the hydrophilic 2D channels of 3 in the smectic membrane containing imidazolium moieties is expected to be approximately 1 nm [ 12 , 13 ], which is also much smaller than viruses. The Sm membrane showed the highest LRV among the LC nanostructured membranes.…”

“…The virus rejection for all membranes was tested using 25 mm membrane filtration units with agitation (Advantec ® UHP-25K, Tokyo, Japan) connected to a reservoir containing a feed solution of Milli-Q water (Advantec ® RP-2) [ 10 – 13 ]. Details for the preparation of feed virus solution are presented in the Supporting Information.…”

“…For example, we developed nanostructured membranes with three-dimensional (3D) nano ionic channels from an ionic bicontinuous cubic (Cub bi ) LC monomer with a taper-shaped mesogen [ 10 ]. 1D nanochannels of diol moieties were obtained from supramolecular columnar (Col) LC mixtures [ 11 ], and 2D ionic channels were prepared from ionic smectic (Sm) LC monomers [ 12 , 13 ]. These LC membranes show high levels of rejection of bacteriophage Qβ (Qβ).…”