Masafumi Yoshio

Noncovalent Approach to One-Dimensional Ion Conductors: Enhancement of Ionic Conductivities in Nanostructured Columnar Liquid Crystals

Noncovalent design of new liquid-crystalline (LC) columnar assemblies based on an ionic liquid has shown to be useful to achieve anisotropic high ionic conductivities. An equimolar mixture of an ionic liquid, 1-butyl-3-methylimidazolium bromide, and 3-[3,4,5-tri(octyloxy)benzoyloxy]propane-1,2-diol, which is partially miscible with the ionic liquid, exhibits an LC hexagonal columnar phase from -4 to 63 degrees C. This columnar supramolecular assembly forming the nanostructures shows the one-dimensional (1D) ionic conductivity of 3.9 x 10(-3) S cm(-1) at 50 degrees C along the column, which is more than 700 times higher than that of the corresponding covalent-type columnar ionic liquid, 1-methyl-3-[3,4,5-tri(octyloxy)benzyl]imidazolium bromide, which is 5.3 x 10(-6) S cm(-1) at 50 degrees C. This significant enhancement of the ionic conductivity is attributed to the increase of the mobility of the ionic part.

3D Interconnected Ionic Nano-Channels Formed in Polymer Films: Self-Organization and Polymerization of Thermotropic Bicontinuous Cubic Liquid Crystals

Thermotropic bicontinuous cubic (Cub(bi)) liquid-crystalline (LC) compounds based on a polymerizable ammonium moiety complexed with a lithium salt have been designed to obtain lithium ion-conductive all solid polymeric films having 3D interconnected ionic channels. The monomer shows a Cub(bi) phase from -5 to 19 °C on heating. The complexes retain the ability to form the Cub(bi) LC phase. They also form hexagonal columnar (Col(h)) LC phases at temperatures higher than those of the Cub(bi) phases. The complex of the monomer and LiBF(4) at the molar ratio of 4:1 exhibits the Cub(bi) and Col(h) phases between -6 to 19 °C and 19 to 56 °C, respectively, on heating. The Cub(bi) LC structure formed by the complex has been successfully preserved by in situ photopolymerization through UV irradiation in the presence of a photoinitiator. The resultant nanostructured film is optically transparent and free-standing. The X-ray analysis of the film confirms the preservation of the self-assembled nanostructure. The polymer film with the Cub(bi) LC nanostructure exhibits higher ionic conductivities than the polymer films obtained by photopolymerization of the complex in the Col(h) and isotropic phases. It is found that the 3D interconnected ionic channels derived from the Cub(bi) phase function as efficient ion-conductive pathways.

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.

Self‐Organized Liquid‐Crystalline Nanostructured Membranes for Water Treatment: Selective Permeation of Ions

A membrane with ordered 3D ionic nanochannels constructed by in situ photopolymerization of a thermotropic liquid-crystalline monomer shows high filtration performance and ion selectivity. The nanostructured membrane exhibits water-treatment performance superior to that of an amorphous membrane prepared from the isotropic melt of the monomer. Self-organized nanostructured membranes have great potential for supplying high-quality water.

Macroscopically Ordered Polymer/CaCO3 Hybrids Prepared by Using a Liquid-Crystalline Template†

Biominerals are organic/inorganic hybrids formed by living organisms under mild conditions. Biomacromolecules such as polysaccharides, proteins, and glycoproteins serve as templates that control the crystal growth of biominerals and thus result in the formation of highly organized hybrid structures. Recently, intensive work has been focused on the development of biomineralization-inspired hybrid materials based on CaCO3. [1–14] For the preparation of these novel hybrid materials exhibiting versatile properties such as mechanical stability, optical properties, and biofunctionality, it is essential to control the orientation and structure of both inorganic and organic components on the macroscopic scale. However, such control over orientation and morphology of the components has not yet been effectively achieved. Our intention was to obtain highly organized hybrid materials using macroscopically ordered templates based on liquidcrystalline (LC) macromolecules. Herein we report on the preparation of ordered polymer/CaCO3 hybrids by using the macroscopically ordered LC states of a semisynthetic chitin derivative as template. Only a couple of studies on the use of ordered matrices have been reported, and these matrices were derived from biosystems. Mann and co-workers demonstrated the formation of ordered porous chitin/silica composites using a macroscopically ordered b-chitin matrix obtained from cuttlebone. Falini and co-workers used the aligned b-chitin obtained from the pen of a squid as a matrix for calcium salts, which resulted in the formation of oriented crystals. If we could use and control the ordering processes of synthetic or semisynthetic polymer matrices, a variety of self-organized hybrid macroscale structures could be obtained more easily. In the formation of thin-film CaCO3 crystals, the minerals are deposited on solid polymer matrices in the presence of acidic soluble macromolecules. Cooperation of solid matrices such as polysaccharides and poly(vinyl alcohol) with acidic macromolecules is essential to form hybrid thin-film structures. We previously reported on the formation of unidirectionally oriented thin-film crystals of CaCO3 on a randomly oriented chitin matrix in the presence of an acidic natural peptide isolated from the exoskeleton of a crayfish. However, the size of these thin films was only 10 4 10 mm and the direction of orientation of each film was random on the macroscopic scale because of the random arrangement of the chitin matrix. Furthermore, acidic peptides having specific sequences of amino acids were required. Our approach here is to obtain highly ordered hybrids using LC templates. Liquid crystals can form large domains of oriented molecules on the macroscopic scale. We expected that oriented polymeric solid matrices processed through their LC states should serve as templates to induce unidirectional crystal growth of CaCO3. The ordered chitin matrix was prepared by processing and deprotection of a corresponding LC chitin derivative obtained by carbamation of chitin (Figure 1). The chitin phenylcarbamate formed a lyotropic

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.

Electric Field-Assisted Alignment of Self-Assembled Fibers Composed of Hydrogen-Bonded Molecules Having Laterally Fluorinated Mesogens

Aligned fibrous aggregates of amide compounds having laterally fluorinated aromatic mesogens have been successfully obtained by the application of the alternating current electric field (1.0 V/microm, 1 kHz) in dodecylbenzene. In contrast, randomly entangled fibers are formed in the solvent without electric fields. For the analogous compounds without fluorine substituent, no aligned fibrous aggregates have been obtained under the electric fields. The electric field alignment of the fibers should be assisted by the fluorinated rod-shaped mesogens that exhibit negative dielectric anisotropy.

Functional Liquid-Crystalline Polymers for Ionic and Electronic Conduction

Liquid-crystalline (LC) polymers that exhibit ionic or electronic conduction are described. Anisotropic and efficient transportation of electrons and ions is expected for these materials. The ordered LC nanostructures of LC polymers having ion- or electron-active moieties are important for efficient anisotropic transport. For electron-conductive materials, we focus on side-chain LC polymers.

A Planarized Triphenylborane Mesogen: Discotic Liquid Crystals with Ambipolar Charge‐Carrier Transport Properties

A discotic liquid-crystalline (LC) material, consisting of a planarized triphenylborane mesogen, was synthesized. X-ray diffraction analysis confirmed that this compound forms a hexagonal columnar LC phase with an interfacial distance of 3.57 Å between the discs. At ambient temperature, this boron-centered discotic liquid crystal exhibited ambipolar carrier transport properties with electron and hole mobility values of approximately 10(-3) and 3×10(-5)  cm(2)  V(-1)  s(-1), respectively.

m x n stacks of discrete aromatic stacks in solution.

Septuple columnar stacks of large aromatic molecules with solubilizing side chains have been synthesized via one-step multicomponent self-assembly. At increased concentrations in aqueous solution, m x n aggregates of aromatic stacks form. The simple addition of water induces lyotropic liquid-crystalline mesophases.