Silver to Gold Metallic Luster Changes in Stimuli-Responsive Diacetylene Derivatives Uniquely Arranged within Crystals.

Eye-catching metallic luster materials, especially those whose colors can be controlled by external stimuli, have many potential applications. Here, we present a silver luster material that changes color to gold upon UV irradiation. Diacetylene (DA) derivatives with stilbenes introduced via linkers at both ends ( ( = 1-6)) exhibited significantly different metallic luster and color change behaviors depending on the linker carbon number ().

Positions of Chiral Alkoxy Groups Responsible for Ferroelectricity in a Columnar Liquid Crystal Phase of Diphenylureas with Six Alkoxy Groups.

The columnar polarization direction of ferroelectric columnar liquid crystals can be switched by applying an external electric field, and the polarization direction can be maintained, even after the electric field is removed. If the polarization direction of each column in ferroelectric columnar liquid crystals can be switched and maintained, then ultrahigh-density memory devices can be generated. Recently, we found that the columnar phase of ,'-bis(3,4,5-tri()-citronellyloxyphenyl)urea () shows ferroelectricity, whereas that of ,'-bis(3,4,5-tridecyloxyphenyl)urea () does not.

Magnetic Supramolecular Spherical Arrays: Direct Formation of Micellar Cubic Mesophase by Lanthanide Metallomesogens with 7-Coordination Geometry.

Here, an unprecedented phenomenon in which 7-coordinate lanthanide metallomesogens, which align via hydrogen bonds mediated by coordinated HO molecules, form micellar cubic mesophases at room temperature, creating body-centered cubic (BCC)-type supramolecular spherical arrays, is reported. The results of experiments and molecular dynamics simulations reveal that spherical assemblies of three complexes surrounded by an amorphous alkyl domain spontaneously align in an energetically stable orientation to form the BCC structure. This phenomenon differs greatly from the conventional self-assembling behavior of 6-coordinated metallomesogens, which form columnar assemblies due to strong intermolecular interactions.

Janus metallic film with gold and silver luster by electroless deposition of silver using poly(dopamine acrylamide) thin film.

Films that exhibit different metallic luster on the front and back, called Janus metallic films, have broad applications ranging from design materials to optical devices. However, the fabrication of these films is often a complicated process involving multiple metal deposition steps, thermal annealing, and calcination. Herein, we report the simple preparation of a Janus metallic film by electroless deposition of silver on a poly(dopamine acrylamide) (pDOPAm) thin film.

Molecular Dynamics Studies of the Ho(III) Aqua-tris(dibenzoylmethane) Complex: Role of Water Dynamics.

The seven-coordinate Ho(III) aqua-tris(dibenzoylmethane)(DBM) complex, referred to as Ho-(DBM)·HO, was first reported in the late 1960s. It has a threefold symmetric structure, with Ho at the center of three dibenzoylmethane ligands and hydrogen-bonded water to ligands. It is considered that the hydrogen bonds between the water molecule and the ligands surrounding Ho play an important role in the formation of its symmetrical structure.

Crack-Free Structural Color Materials Prepared without Disrupting the Particle Arrangement by Controlling the Internal Stress Relaxation and Interactions of the Melanin Particles.

In fabricating structural color materials with assembled colloidal particles, there is a trade-off between the internal stresses acting on the particles and the interactions between the particles during solvent volatilization. It is crucial to fabricate crack-free materials that maintain the periodic arrangements of the particles by understanding the mechanism for crack initiation. Here, we focused on the composition and additives of melanin particle dispersions to obtain crack-free structural color materials without disturbing the particle arrangements.

A Flexible and Robust Structural Color Film Obtained by Assembly of Surface-Modified Melanin Particles.

In this study, core-shell-hairy-type melanin particles surface modified with a polydopamine shell layer and a polymer brush hairy layer were fabricated and assembled to readily obtain bright structural color films. The hot pressing of freeze-dried samples of melanin particles decorated with a hydrophilic, low glass transition temperature polymer brush results in films that exhibit an angle-dependent structural color due to a highly periodic microstructure, with increased regularity in the arrangement of the particle array due to the fluidity of the particles. Flexible, self-supporting, and easy-to-cut and process structural color films are obtained, and their flexibility and robustness are demonstrated using compression tests.

Chiral Self-Sorting and the Realization of Ferroelectricity in the Columnar Liquid Crystal Phase of an Optically Inactive ,'-Diphenylurea Derivative Possessing Six (±)-Citronellyl Groups.

An axially polar-ferroelectric columnar liquid crystal (AP-FCLC) phase that exhibits both switching and maintenance of the macro-polarity in the column axis direction has been achieved in an ,'-bis(3,4,5-trialkoxyphenyl)urea compound (-) prepared from (±)-citronellyl bromide. Although it had been thought that chirality is necessary to achieve the AP-FCLC phase from our previous study, the optically inactive compound which is a mixture of 21 stereoisomers, generated an AP-FCLC phase. We confirmed its ferroelectricity and investigated the mechanism for realizing the AP-FCLC phase using optoelectronic experiments, X-ray diffraction, and circular dichroism spectroscopy.

Control of Structural Coloration by Natural Sunlight Irradiation on a Melanin Precursor Polymer Inspired by Skin Tanning.

Natural melanin affects the reflection and absorption of light, and it is known as an important element in producing bright structural colors in nature. In this study, we prepared core-shell particles using a melanin precursor polymer, that is, polytyrosine (PTy), as a shell layer by the oxidative polymerization of tyrosine ethyl ester (Ty) in the presence of cerium oxide (CeO) core particles. Inspired by skin tanning, irradiating the CeO@PTy core-shell particles with UV or natural sunlight caused melanization by extending the π-conjugated length of PTy, producing colloidal particles with the ability to absorb light.

Progress in polydopamine-based melanin mimetic materials for structural color generation.

Structural color is a color derived from optical interaction between light and a microstructure and is often seen in nature. Natural melanin plays an important role in bright structural coloration. For example, the vivid colors of peacock feathers are due to structural colors.

Effect of the Polydopamine Composite Method on Structural Coloration: Comparison of Binary and Unary Assembly of Colloidal Particles.

Melanin influences light reflection and absorption and is known to be one of the elements producing structural color, such as that in the feathers of birds. In this study, we used polydopamine (PDA), an artificial melanin, as a light-absorbing material and examined in detail the effect of its composite method on the structural color. The following two composite methods were investigated using cerium(IV) oxide (CeO) particles as a core particle: binary coassembly of CeO and PDA particles and unary assembly of CeO@PDA core-shell particles.

Preparation of liquid crystal nanocapsules by polymerization of oil-in-water emulsion monomer droplets.

Liquid crystal nanocapsules (LC-Nanocapsules) were prepared by miniemulsion polymerization of the oil-in-water emulsion monomer droplets dissolving the liquid crystal (LC) compounds. In order to establish the preparation conditions of LC-Nanocapsules exhibiting the liquid crystallinity, the effects of the capsule wall-forming monomers and the crosslinking agent concentration on the capsule structure were investigated in detail. The monodisperse colloidal products covered with the robust polymer shell wall was successfully prepared by the polymerization of the emulsion monomer droplets obtained through the phase inversion temperature emulsification technique using the amphiphilic block copolymer as an emulsifier.

Adhesion Control of Branched Catecholic Polymers by Acid Stimulation.

Biomimetic material design is a useful method for producing new functional materials. In recent years, catecholic polymers inspired from the adhesion mechanism of marine organisms have attracted attention. Here, we demonstrated the preparation of catecholic polymers by reversible addition-fragmentation chain transfer (RAFT) polymerization of an acetonide-protected catecholic monomer, that is, -(2-(2,2-dimethylbenzo-1,3-dioxol-5-yl)ethyl)-acrylamide (DDEA).

Does Introduction of a Bent Tail Stabilize Biaxiality and Lateral Switching Behavior of Smectic A Liquid Crystal Phases of Rodlike Molecules?

By introducing an oleyl group at the end of the straight rodlike molecule, the effect of the tail shape on the liquid crystallinity, biaxiality, and lateral switching behavior of the smectic A phase was investigated. Three types of molecules possessing a fluorinated phenyl (pentafluorophenyl, 2,3,4-trifluorophenyl, or 2,3-difluorophenyl) group and a cis-octadec-9-enyl group were synthesized, and their liquid crystallinities were compared with the corresponding molecules with a straight alkyl ( trans-octadec-9-enyl or n-octadecanyl) group. In switching experiments, the molecules with a bent terminal chain showed higher spontaneous polarization ( P) values than those with a straight terminal chain.

Preparation of photochromic liquid core nanocapsules based on theoretical design.

Photochromic materials have attracted considerable attention for their practical applications in optoelectronic devices. In this study, we developed the photochromic liquid core nanocapsules by polymerization of oil-in-water (O/W) nanoemulsion monomer droplets on the basis of Hansen solubility parameters. The thermoresponsive amphiphilic block copolymers (POEGMA-b-PSt and POEGMA-b-PMMA) were synthesized by sequential reversible addition fragmentation chain transfer (RAFT) polymerization of hydrophilic oligo(ethylene glycol) methyl ether methacrylate and hydrophobic styrene or MMA.

Ellipsoidal Artificial Melanin Particles as Building Blocks for Biomimetic Structural Coloration.

Inspired by the structural coloration of anisotropic materials in nature, we demonstrate the preparation of structural color materials by the assembly of anisotropic particles. Spherical artificial melanin particles consisting of a polystyrene core and polydopamine shell were stretched asymmetrically to form uniform-sized ellipsoidal particles with different aspect ratios. The aspect ratio and assembly method of the ellipsoidal particles influence the structural coloration, indicating that the particle shape is one of the important parameters for controlling the structural coloration.

Melanin Precursor Influence on Structural Colors from Artificial Melanin Particles: PolyDOPA, Polydopamine, and Polynorepinephrine.

Polydopamine (PDA) is of interest as a mimetic material of melanin to produce structural color materials. Herein, to investigate the influence of the material composition of the artificial melanin particles on structural color, we demonstrated the preparation of core-shell particles by polymerization of norepinephrine or 3,4-dihydroxyphenylalanine, which are melanin precursors similar to dopamine, in the presence of polystyrene particles. It was revealed that the arrays of the prepared particles produce high-visibility structural color because of absorption of scattering light.

A metal-lustrous porphyrin foil.

A metal-lustrous self-standing film, named "porphyrin foil", was formed from a glass-forming polymeric porphyrin. The amorphous glass nature of the porphyrin foil played a key role in spontaneously producing a smooth surface. Its sharp contrast in intense absorption and specular reflection of light at each wavelength provided a brilliant metallic lustre.

Polydopamine-Based 3D Colloidal Photonic Materials: Structural Color Balls and Fibers from Melanin-Like Particles with Polydopamine Shell Layers.

Nature creates beautiful structural colors, and some of these colors are produced by nanostructural arrays of melanin. Polydopamine (PDA), an artificial black polymer produced by self-oxidative polymerization of dopamine, has attracted extensive attention because of its unique properties. PDA is a melanin-like material, and recent studies have reported that photonic materials based on PDA particles showed structural colors by enhancing color saturation through the absorption of scattered light.

Structural Color Tuning: Mixing Melanin-Like Particles with Different Diameters to Create Neutral Colors.

We present the ability to tune structural colors by mixing colloidal particles. To produce high-visibility structural colors, melanin-like core-shell particles composed of a polystyrene (PSt) core and a polydopamine (PDA) shell, were used as components. The results indicated that neutral structural colors could be successfully obtained by simply mixing two differently sized melanin-like PSt@PDA core-shell particles.

Shape-Assisted Self-Organization in Highly Disordered Liquid Crystal Phases.

In achiral rod-like molecules, a nematic phase is the most disordered liquid crystal phase, which only has one-directional order in the direction of the molecular long axis. A dumbbell-shaped molecule (compound 3: R-C H -CH=CH-C H -CH=CH-C H -R, (R=nC H )), and its liquid crystal phase (X phase) are reported, which exhibit high scattering without thermal fluctuation between two nematic phases under a polarized light optical microscope. The X phase was investigated by X-ray diffraction, scanning electron microscopy, atomic force microscopy, and molecular dynamics simulation.

Full-Color Biomimetic Photonic Materials with Iridescent and Non-Iridescent Structural Colors.

The beautiful structural colors in bird feathers are some of the brightest colors in nature, and some of these colors are created by arrays of melanin granules that act as both structural colors and scattering absorbers. Inspired by the color of bird feathers, high-visibility structural colors have been created by altering four variables: size, blackness, refractive index, and arrangement of the nano-elements. To control these four variables, we developed a facile method for the preparation of biomimetic core-shell particles with melanin-like polydopamine (PDA) shell layers.

Polystyrene latex particles containing europium complexes prepared by miniemulsion polymerization using bovine serum albumin as a surfactant for biochemical diagnosis.

Luminescent particles have been attracting significant attention because they can be used in biochemical applications, such as detecting and imaging biomolecules. In this study, luminescent polystyrene latex particles were prepared through miniemulsion polymerization of styrene with dissolved europium complexes in the presence of bovine serum albumin (BSA) and poly(ethylene glycol) monomethoxy methacrylate as surfactants. The solubility of the europium complex in styrene has a strong effect on the yield of the particle.

Polydopamine Particle as a Particulate Emulsifier.

"Pickering-type" emulsions were prepared using polydopamine (PDA) particles as a particulate emulsifier and -dodecane, methyl myristate, toluene or dichloromethane as an oil phase. All the emulsions prepared were oil-in-water type and an increase of PDA particle concentration decreased oil droplet diameter. The PDA particles adsorbed to oil⁻water interface can be crosslinked using poly(ethylene imine) as a crosslinker, and the PDA particle-based colloidosomes were successfully fabricated.