Bartolome Soberats

3D Anhydrous Proton-Transporting Nanochannels Formed by Self-Assembly of Liquid Crystals Composed of a Sulfobetaine and a Sulfonic Acid

Herein we describe anhydrous proton transportation through 3D interconnected pathways formed by self-assembled molecular complexes. A thermotropic bicontinuous cubic (Cub(bi)) phase has been successfully obtained by mixing a wedge-shaped sulfobetaine with benzenesulfonic acid in different ratios. These ionic complexes exhibit the Cub(bi) phase in a wide range of temperatures, while the single zwitterionic compound shows only a columnar hexagonal phase, and benzenesulfonic acid is nonmesomorphic. Anhydrous proton conduction on the order of 10(-4) S cm(-1) has been achieved for the mixture in the Cub(bi) phase over 100 °C, which can be useful for the development of new electrolytes for the next generation of fuel cells.

Macroscopic Photocontrol of Ion-Transporting Pathways of a Nanostructured Imidazolium-Based Photoresponsive Liquid Crystal

The photocontrol of the macroscopic alignment of nanostructured 2D ion-transporting pathways is described. The uniplanar homogeneous alignment of the thermotropic smectic (Sm) liquid-crystalline (LC) phase has been successfully achieved via photoinduced reorientation of the azobenzene groups of the imidazolium-based LC material. The ionic layers of the Sm LC phase are macroscopically oriented perpendicular to the surface of the glass substrate. The oriented films show anisotropic ion conduction in the Sm phase. This is the first example of the macroscopic photoalignment of ion-conductive LC arrays. Reversible switching of homeotropic and homogeneous alignments has also been achieved for the LC material. These materials and the alignment methodology may be useful in the development of ion-based circuits and memory devices.

Zwitterionic liquid crystals as 1D and 3D lithium ion transport media

We describe the development of self-assembled one- and three-dimensional lithium ion conductors composed of zwitterionic liquid crystals, lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) and propylene carbonate (PC). Two types of wedge-shaped zwitterions based on imidazolium dicyanoethenolate and sulfonate were synthesized. These compounds alone show liquid-crystalline (LC) columnar hexagonal (Colh) phases and low ionic conductivities (10−8 to 10−7 S cm−1). The increase in the ionic conductivities was achieved by the addition of LiTFSI (10−5 S cm−1) followed by that of PC (10−4 S cm−1). Moreover, LC bicontinuous cubic (Cubbi) phases are induced by tuning the ionic nature of the zwitterionic liquid crystal with the ratio of LiTFSI and PC. The dissociation of LiTFSI in the zwitterions and the ion–dipole interaction between the lithium ions and PC are shown to be significant keys for the enhancement of the conductivities and stabilization of the nanosegregated LC structures.

Ionic Switch Induced by a Rectangular–Hexagonal Phase Transition in Benzenammonium Columnar Liquid Crystals

We demonstrate switching of ionic conductivities in wedge-shaped liquid-crystalline (LC) ammonium salts. A thermoreversible phase transition between the rectangular columnar (Colr) and hexagonal columnar (Colh) phases is used for the switch. The ionic conductivities in the Colh phase are about four orders of magnitude higher than those in the Colr phase. The switching behavior of conductivity can be ascribed to the structural change of assembled ionic channels. X-ray experiments reveal a highly ordered packing of the ions in the Colr phase, which prevents the ion transport.

Use of a protic salt for the formation of liquid-crystalline proton-conductive complexes with mesomorphic diols

We herein report that molecular assembly of wedge-shaped mesomorphic diols and a protic salt results in the formation of anhydrous one-dimensional (1D) and 2D proton-conductive materials. The protic salt has been obtained by stoichiometric neutralization of imidazole with benzenesulfonic acid. The protic salt is incorporated into the hydrogen-bonded networks of the hydroxyl groups of the mesomorphic diols. This confined protic salt in the nanochannels exhibits enhanced ionic conductivities by three-orders of magnitude compared with those of the pure protic salt in the solid state, indicating that the imidazolium salt forms a mobile state in the liquid-crystalline nanostructures. These self-assembled and ordered materials based on protic salts may be promising candidates for the application as anhydrous proton-conducting electrolytes in fuel cells.

Development of Nanostructured Water Treatment Membranes Based on Thermotropic Liquid Crystals: Molecular Design of Sub‐Nanoporous Materials

Abstract Supply of safe fresh water is currently one of the most important global issues. Membranes technologies are essential to treat water efficiently with low costs and energy consumption. Here, the development of self‐organized nanostructured water treatment membranes based on ionic liquid crystals composed of ammonium, imidazolium, and pyridinium moieties is reported. Membranes with preserved 1D or 3D self‐organized sub‐nanopores are obtained by photopolymerization of ionic columnar or bicontinuous cubic liquid crystals. These membranes show salt rejection ability, ion selectivity, and excellent water permeability. The relationships between the structures and the transport properties of water molecules and ionic solutes in the sub‐nanopores in the membranes are examined by molecular dynamics simulations. The results suggest that the volume of vacant space in the nanochannel greatly affects the water and ion permeability.