Faculty Profiles - TAKEOKA, Yukikazu

Papers - TAKEOKA, Yukikazu

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Photo-control of spatio-temporal oscillation in a gel system with light-sensitive Belousov-Zhabotinsky reaction

Shinohara S., Nagano S., Takeoka Y., Seki T., Yoshida R.

Polymer Preprints, Japan Vol. 54 ( 1 ) 2005.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Polymer Preprints, Japan

A gel that is prepared by the copolymerization of ruthenium complex as a light sensitive catalyst for the Belousov-Zhabotinsky (BZ) reaction and N-isopropylacrylamide has been known to convert spatio-temporal chemical oscillation into physical motion with the BZ-reaction. We are concerned about the control of the physical motion using the light sensitive BZ-reaction. The physical motion was observed with the change in the structural colors that depend on the swelling of the gel. For the alteration in the physical motion by light irradiation, the spectral changes with the structural colors and the images will be reported.

Scopus

Electrically induced structural color change in periodically ordered porous gels having ionized groups

Ueno K., Matsubara K., Takeoka Y., Watanabe M.

Polymer Preprints, Japan Vol. 54 ( 1 ) 2005.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Polymer Preprints, Japan

Periodically ordered porous gels having immobilized ionic groups were prepared using a close-packed colloidal crystal as a template. The optical properties of the porous gels were dynamically measured by reflection spectroscopy, when dc voltage of 1.80 V was applied between the electrodes in an aqueous solution, onto one of which the porous gels were placed. In this study, the porous hydrogels composed of thermo- and pH-sensitive building blocks were used. The porous hydrogels could drastically convert their optical properties in response to the local pH change induced by water electrolysis due to the voltage application. Moreover, we could precisely control such optical properties with altering temperature of the solution concurrently with applying the voltage.

Scopus

構造色を示すゲル〜鋳型を用いたゲルの機能化〜

竹岡敬和

現代化学 412 page： 24 - 31 2005

発色性ゲルから観測される色の制御

竹岡敬和

化学工業 10 page： 53 - 57 2005

Simple and precision design of porous gel as a visible indicator for ionic species and concentration

H Saito, Y Takeoka, M Watanabe

CHEMICAL COMMUNICATIONS ( 17 ) page： 2126 - 7 2003.9

Language：English Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY

Here we report the design and synthesis of a novel porous gel for an ionic visible indicator. The rapid-responsive porous gel which reveals color changes depending on a potassium ion concentration was prepared using a templating technique.

DOI： 10.1039/b304306a

Web of Science

PubMed

Effects of salinity stress on the seminal root tip ultrastructures of rice seedlings (Oryza sativa L.)

Rahman S., Matsumuro T., Miyake H., Takeoka Y.

Plant Production Science Vol. 4 ( 2 ) page： 103 - 111 2001

Language：English Publishing type：Research paper (scientific journal) Publisher：Plant Production Science

Growth and structural changes in the seminal root tip of rice seedlings (Oryza sativa L. cv. Nipponbare) in response to NaCl salinity were studied. Seedlings were grown in agar medium with 0, 0.1, 0.3, 1.0, 2.0 and 3.0% NaCl (agar culture), and in water with 0, 0.01, 0.03, 0.06 and 0.1% NaCl (water culture). Seedling growth was significantly suppressed by higher concentrations of NaCl. The effect of NaCl appeared faster in water culture than in agar culture. In both agar and water cultures, root growth was markedly suppressed over shoot growth. Under saline conditions, epidermis, cortex and root cap cells appear to be damaged to a greater extent than the meristem and stelar cells. The most notable ultrastructural change in response to salinity was the development and increment of vacuoles, which seem to provide a space for accumulation of excess ions. Many electron dense deposits were observed in the larger vacuoles of the epidermal and cortical cells. Under saline conditions, cell wall thickening of the epidermis, an increase in endoplasmic reticulum, myelin figures, less compact Golgi bodies and inhibited production of Golgi vesicles were also observed.

DOI： 10.1626/pps.4.103

Scopus

Production of intergeneric hybrid calli from C-3 and C-4 species of Amaranthaceae through protoplast fusion

Mastuti, R; Miyake, H; Taniguchi, T; Takeoka, Y

JAPANESE JOURNAL OF CROP SCIENCE Vol. 66 ( 3 ) page： 456 - 465 1997.9

Ultrastructural studies on the fusion product between protoplasts of mung bean and adzuki bean

Mikaye, IH; Taniguchi, T; Takeoka, Y

JAPANESE JOURNAL OF CROP SCIENCE Vol. 65 ( 2 ) page： 330 - 339 1996.6

RELATIONSHIPS BETWEEN VASCULAR BUNDLES OF PANICLE NECK INTERNODE AND CHARACTERS OF HEAD UNDER DIFFERENT PLANTING DENSITIES AND NITROGEN FERTILIZERS APPLIED IN ORYZA-SATIVA L

CUI HJ, JIN RZ, TAKEOKA Y

JAPANESE JOURNAL OF CROP SCIENCE Vol. 64 ( 2 ) page： 216 - 220 1995.6

Detailed Analysis of Peripheral Reflection from a Photonic Ball

Ryosuke Ohnuki, Miki Sakai, Yukikazu Takeoka, Shinya Yoshioka

Advanced Photonics Research Vol. 2 ( 12 ) page： 2100131 - 2100131 2021.12

Bioinspired Color Elastomers Combining Structural, Dye, and Background Colors International journal

Pei Shi, Eiji Miwa, Jialei He, Miki Sakai, Takahiro Seki, Yukikazu Takeoka

ACS Applied Materials & Interfaces Vol. 13 ( 46 ) page： 55591 - 55599 2021.11

Language：English Publishing type：Research paper (scientific journal) Publisher：American Chemical Society ({ACS})

Organisms that alter body color undergo color change in response to environmental variations and stimuli by combining chromatophores that develop colors by various mechanisms. Inspired by their body color changes, we can develop sensors and optical materials that change colors in response to multiple stimuli, such as mechanical and light stimuli. In this study, we report on bioinspired composite elastomers that exhibit various color changes as the pigment color, structural color, and background color change. These composite elastomers exhibit structural colors due to their fine structures in which fine silica particles form colloidal crystals, and the structural colors reversibly change as the elastomers elongate. Furthermore, photochromic dyes can reversibly change color depending on the wavelength of irradiated light when they are introduced to the composite elastomers. Since the structural color is one of the three primary colors of light and the pigment color is the color that corresponds to the three primary colors of a pigment, each color becomes vivid when the background color is black or white. Thus, we clarify that the composite elastomers exhibit various color changes due to the combination of structural color change in response to the mechanical stimulus, pigment color change in response to light irradiation, and background color change.

DOI： 10.1021/acsami.1c19471

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Scopus

PubMed

Mechanical Properties of Homogeneous Polymer Networks Prepared by Star Polymer Synthesis Methods

Yusuke Baba, Guohao Gao, Mitsuo Hara, Takahiro Seki, Kotaro Satoh, Masami Kamigaito, Taiki Hoshino, Kenji Urayama, Yukikazu Takeoka

Macromolecules Vol. 54 ( 22 ) page： 10468 - 10476 2021.11

Language：English Publishing type：Research paper (scientific journal) Publisher：American Chemical Society ({ACS})

To investigate the effect of the network structure on the mechanical properties of a polymer network formed from a certain polymer, we should prepare polymer networks with clearly different network structures made of the same polymer and compare the mechanical properties of these polymer networks. If a living radical polymerization method is applied to the same monomer constituting the polymer network with a nonuniform network structure obtained by conventional free-radical polymerization, it is possible to obtain a polymer network with a uniform network structure in which the molecular weights of the polymer chains bonded to the cross-linking points are uniform and the number of chains bonded to the cross-linking points is constant. In this study, we worked on the synthesis of a polymer network with a uniform network structure by combining two different types of star-shaped polymer synthesis methods using living radical polymerization, i.e., the core-first method and the linking method. In the core-first method, it was possible to synthesize a star-shaped polymer with a narrow molecular weight distribution in a state with a molecular weight corresponding to the charging ratio of the initiator with four initial groups and the monomer. We confirmed that the polymer network obtained by binding the star-shaped polymers by the linking method had a uniform structure, even when swollen with a good solvent or dried, from small-angle X-ray scattering. Depending on the molecular weight of the star-shaped polymer obtained by the core-first method and the amount of the cross-linking agent added for the linking method, the mesh size of the network could be changed while having a uniform network structure. The dried polymer network with uniform network structures exhibited significantly higher values of fracture extensibility and energy than those with nonuniform network structures via conventional free-radical polymerization, when compared at the same monomer and cross-linker concentration.

DOI： 10.1021/acs.macromol.1c01680

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Scopus

Morphologically Diverse Micro- and Macrostructures Created via Solvent Evaporation-Induced Assembly of Fluorescent Spherical Particles in the Presence of Polyethylene Glycol Derivatives. International journal

Mina Han, Ikue Abe, Kazunori Matsuura, Yukikazu Takeoka, Takahiro Seki

Molecules (Basel, Switzerland) Vol. 26 ( 14 ) 2021.7

Language：English Publishing type：Research paper (scientific journal) Publisher：MDPI

The creation of fluorescent micro- and macrostructures with the desired morphologies and sizes is of considerable importance due to their intrinsic functions and performance. However, it is still challenging to modulate the morphology of fluorescent organic materials and to obtain insight into the factors governing the morphological evolution. We present a facile bottom-up approach to constructing diverse micro- and macrostructures by connecting fluorescent spherical particles (SPs), which are generated via the spherical assembly of photoisomerizable azobenzene-based propeller-shaped chromophores, only with the help of commercially available polyethylene glycol (PEG) derivatives. Without any extra additives, solvent evaporation created a slow morphological evolution of the SPs from short linear chains (with a length of a few micrometers) to larger, interconnected networks and sheet structures (ranging from tens to >100 µm) at the air-liquid interface. Their morphologies and sizes were significantly dependent on the fraction and length of the PEG. Our experimental results suggest that noncovalent interactions (such as hydrophobic forces and hydrogen bonding) between the amphiphilic PEG chains and the relatively hydrophobic SPs were weak in aqueous solutions, but play a crucial role in creating the morphologically diverse micro- and macrostructures. Moreover, short-term irradiation with visible light caused fast morphological crumpling and fluorescence switching of the obtained structures.

DOI： 10.3390/molecules26144294

Web of Science

Scopus

PubMed

Nonturbid Fast Temperature-Responsive Hydrogels with Homogeneous Three-Dimensional Networks by Two Types of Star Polymer Synthesis Methods

DoWoo Kwon, Yuto Jochi, Yuumi Okaya, Takahiro Seki, Kotaro Satoh, Masami Kamigaito, Taiki Hoshino, Kenji Urayama, Yukikazu Takeoka

Macromolecules Vol. 54 ( 12 ) page： 5750 - 5764 2021.6

Language：English Publishing type：Research paper (scientific journal) Publisher：American Chemical Society ({ACS})

Temperature-responsive polymer gel can rapidly and reversibly switch its various physical properties and has been used in practical applications including reservoirs for drug delivery systems, cell sheet preparation base materials for regenerative medicine, and switching elements for microchannels. However, the sudden volume shrinkage in the gel with rapid temperature change may cause the formation of a skin layer and the macrophase separation phenomenon of the polymer network. Due to this phenomenon, it usually takes a very long time to reach a thermodynamically stable shrunken state of the gel. By adjusting the heterogeneity of the network structure of the conventional temperature-responsive polymer gel and the monomer arrangement of the polymer, the polymer gel may shrink faster without causing skin layer formation or macrophase separation phenomenon. In this study, almost ideal homogeneous temperature-responsive polymer gels could be synthesized by combining two types of synthetic methods for well-defined star-shaped polymers, i.e., the core-first method with a multifunctional initiator and linking method with a divinyl compound as the cross-linker, using a polymerization system with extremely high living fashion to afford polymer chains with narrow molecular weight distributions. As a result, the temperature-responsive polymer gels derived from N-isopropylacrylamide (NIPA) with almost uniform network structure were successfully prepared, in which the number of polymer chains bonded to the cross-linking points and the molecular weight between them are quite uniform. Due to the high living fashion of the polymerization used in this method, a temperature-responsive copolymer gel composed of NIPA and other hydrophilic monomers could also be synthesized. The polymer gel consisting of star-shaped block polymers of NIPA and dimethylacrylamide (DMA) responded much faster than that with an uncontrolled network structure and uncontrolled monomer sequence distribution, which shrank completely in less than 1/60 time as fast with optical transparency and without either skin layer formation or macrophase separation of the polymer network during shrinkage.

DOI： 10.1021/acs.macromol.1c00446

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Scopus

Silica Nanoparticle Reinforced Composites as Transparent Elastomeric Damping Materials

Fumio Asai, Takahiro Seki, Taiki Hoshino, Xiaobin Liang, Ken Nakajima, Yukikazu Takeoka

ACS Applied Nano Materials Vol. 4 ( 4 ) page： 4140 - 4152 2021.4

Language：English Publishing type：Research paper (scientific journal) Publisher：American Chemical Society (ACS)

Inspired by the structure of the cornea, which is the transparent front part of the eye, we developed a transparent and tough silica composite elastomer consisting of poly[di(ethylene glycol)methyl ether methacrylate] (PMEO(2)MA) and 110 nm spherical silica particles without using an organic cross-linking agent. While filler composite elastomers, such as reinforced rubbers, have complex compositions containing multiple additives (dispersants, plasticizers, vulcanizing agents, etc.), the composition of our composite elastomer is very simple. With an increased amount of silica particles, the fracture energy of the composite elastomer (20.2 MJ m(-3)) was improved by 25 times compared to that of unfilled PMEO(2)MA (0.8 MJ m(-3)). Nanoscale mapping using atomic force microscopy elucidated the presence of an interface layer (IL) of approximately 15 nm thickness with a high elastic modulus near the silica particles in the composite elastomer. The fracture energy of the composite elastomer was found to be a maximum when the particle surface distance was approximately 30 nm. This particle surface distance meant that the ILs were just in contact with each other. The surface charge density and Hansen solubility parameter of the silica particles indicated the ionization of silanol groups and interactions caused by hydrogen bonding between polymer chains and the silica surface. The array of silica particles embedded with intervals of a few nanometers was expected to be able to effectively dissipate deformation energy as heat due to shear strain and friction between the particle surface and polymer matrices. Measurements of the vibration-damping properties revealed that the loss factor of the composite elastomer was significantly higher than that of the unfilled elastomer, indicating that the composite elastomer in this study could be applied as an interlayer film for laminated glass in automotive and architectural applications.

DOI： 10.1021/acsanm.1c00472

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Scopus

Stimuli-Responsive Structural Colored Gel That Exhibits the Three Primary Colors of Light by Using Multiple Photonic Band Gaps Acquired from Photonic Balls International journal

Yumiko Ohtsuka, Miki Sakai, Takahiro Seki, Ryosuke Ohnuki, Shinya Yoshioka, Yukikazu Takeoka

ACS Applied Materials & Interfaces Vol. 12 ( 48 ) page： 54127 - 54137 2020.12

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

A material that can capture changes in environmental stimuli as a color change can be used to develop sensors and displays. By producing an ordered structure in a polymer gel that reflects particular wavelengths of light, we can express the volume change that occurs based on the environment as the change in the wavelength of reflected light, i.e., structural color. To date, many systems have been developed to change the hue of the structural color as a function of temperature, pH, substance, applied force, and so on. However, as is expected from the principle of optical interference, the gel usually shows a red-shift with increasing volume. In this study, we propose a method for preparing structurally colored stimuli-responsive polymer gels that display appropriate color changes according to changes in environmental stimuli. For this purpose, we employ the photonic balls, which are spherical colloidal crystals consisting of monodisperse silica particles, as templates. By combining the wavelength-selective reflection generated from different photonic band gaps of the photonic balls, we succeeded in developing porous stimuli-responsive polymer gels that exhibited various types of color change, which are not observed in conventional systems.

DOI： 10.1021/acsami.0c17687

Web of Science

Scopus

PubMed

Tough and 3D-Printable Poly(2-methoxyethyl Acrylate)-Silica Composite Elastomer with Anti-Platelet Adhesion Property. Reviewed International journal

Fumio Asai, Takahiro Seki, Ayae Sugawara-Narutaki, Kazuhide Sato, Jérémy Odent, Olivier Coulembier, Jean-Marie Raquez, Yukikazu Takeoka

ACS applied materials & interfaces Vol. 12 ( 41 ) page： 46621 - 46628 2020.10

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

Poly(2-methoxyethyl acrylate) (PMEA) has attracted attention as a biocompatible polymer that is used as an antithrombotic coating agent for medical devices, such as during artificial heart and lung fabrication. However, PMEA is a viscous liquid polymer with low Tg, and its physical strength is poor even if a cross-linker is used, so it is difficult to make tough and freestanding objects from it. Here, we design and fabricate a biocompatible elastomer made of tough, self-supporting PMEA-silica composites. The toughness of the composite elastomer increases as a function of silica particle filling, and the stress at break of it is improved from 0.3 MPa to 6.7 MPa. The fracture energy of the composite elastomer with 39.5 vol% silica particles is up to 15 times higher than that of the cross-linked PMEA with no silica particles and the material demonstrates stress-strain behavior that is similar to that of biological soft tissue, which exhibits nonlinear elasticity. In addition, the composite elastomer shows the potential to be an antithrombotic property, while the results of the platelet adhesion test of the composite elastomer show that the number of adhered platelets is not significantly affected by the silica addition. Since the composite elastomer can be rapidly 3D-printed into complex geometries with high resolution features, it is expected to contribute to the development of medical devices from readily available materials.

DOI： 10.1021/acsami.0c11416

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Scopus

PubMed

Composite Elastomer Exhibiting a Stress-Dependent Color Change and High Toughness Prepared by Self-Assembly of Silica Particles in a Polymer Network Reviewed International journal

Eiji Miwa, Kenta Watanabe, Fumio Asai, Takahiro Seki, Kenji Urayama, Jérémy Odent, Jean-Marie Raquez, Yukikazu Takeoka

ACS Applied Polymer Materials Vol. 2 ( 9 ) page： 4078 - 4089 2020.9

Language：English Publishing type：Research paper (scientific journal) Publisher：American Chemical Society ({ACS})

In this study, we developed a composite elastomer exhibiting both mechanical toughness and a structural color change using submicron-sized spherical fine silica particles with a uniform size as fillers and arranging them in a periodic structure in the elastomer. In this composite elastomer, the fine silica particles formed colloidal crystals in a nonclosest-packed state, so that the composite elastomer was very flexible. We showed the possibility for use as strain and stress sensors that can measure the amount of strain applied to and the stress generated in the composite elastomer according to the position of the reflection peak produced by the composite elastomer. In this composite elastomer, both the fracture stress and the fracture strain were improved by increasing the amount of fine silica particles so that the fracture energy and toughness increased. As a result, the fracture energy of the composite elastomer containing 35 vol % fine silica particles was 13.5 times that of the system containing no fine silica particles. In the stress-strain curve observed by uniaxial stretching of this composite elastomer, a shoulderlike change was observed at different positions depending on the content of the fine silica particles, and further stretching resulted in a large energy dissipation. It was also found that after being strained beyond the shoulder position for the composite elastomer containing 44.9 vol % fine silica particles, the composite elastomer became tougher than before it was stretched. This composite elastomer may be toughened by a change in the interaction between the silica-polymer interface that resulted from uniaxial stretching and a dissipation of the energy caused by a change in the particle arrangement. The composite elastomer developed by the present novel method has the ability to be toughened by being subjected to a large strain once and can be a safe material that can avoid sudden fracture.

DOI： 10.1021/acsapm.0c00703

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Scopus

Robust Structurally Colored Coatings Composed of Colloidal Arrays Prepared by the Cathodic Electrophoretic Deposition Method with Metal Cation Additives Reviewed International journal

Kiyofumi Katagiri, Kensuke Uemura, Ryo Uesugi, Naoki Tarutani, Kei Inumaru, Tetsuo Uchikoshi, Takahiro Seki, Yukikazu Takeoka

ACS Applied Materials & Interfaces Vol. 12 ( 36 ) page： 40768 - 40777 2020.9

Language：English Publishing type：Research paper (scientific journal) Publisher：American Chemical Society ({ACS})

Structurally colored coatings composed of colloidal arrays of monodisperse spherical particles have attracted great attention owing to their versatile advantages, such as low cost, resistance to fading, and low impacts on the environment and human health. However, the weak mechanical stability is considered to be a major obstacle for their practical applications as colorants. Although several approaches based on the addition of polymer additives to enhance the adhesion of particles have been reported, the challenge remains to develop a strategy for the preparation of structurally colored coatings with extremely high robustness using a simple process. Here, we have developed a novel approach to fabricate robust structurally colored coatings by cathodic electrophoretic deposition. The addition of a metal salt, i.e., Mg(NO3)(2), to the coating dispersion allows SiO2 particles to have a positive charge, which enables the electrophoresis of SiO2 particles toward the cathode. At the cathode, Mg(OH)(2) codeposits with SiO2 particles because OH- ions are generated by the decomposition of dissolved oxygen and NO3- ions. The mechanical stability of the colloidal arrays obtained by this process is remarkably improved because Mg(OH)(2) facilitates the adhesion of the particles and substrates. The brilliant structural color is maintained even after several cycles of the sandpaper abrasion test. We have also demonstrated the coating on a stainless steel fork. This demonstration reveals that our approach enables a homogeneous coating on a complicated surface. Furthermore, the high durability of the coating is clarified because the coating did not peel off even when the fork was stuck into a plastic eraser. Therefore, the coating technique developed here will provide an effective method for the pervasive application of the structural color as a colorant.

DOI： 10.1021/acsami.0c10588

Web of Science

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PubMed

Monodisperse Silica Nanoparticle-Carbon Black Composite Microspheres as Photonic Pigments Reviewed International journal

Miki Sakai, Hyunji Kim, Yusuke Arai, Takuya Teratani, Youhei Kawai, Yuichi Kuwahara, Keisuke Abe, Yasuhiro Kuwana, Katsuji Ikeda, Kazuhiko Yamada, Yukikazu Takeoka

ACS APPLIED NANO MATERIALS Vol. 3 ( 7 ) page： 7047 - 7056 2020.7

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

The development of nonbleachable colorants made of safe and inexpensive materials is a scientifically important task in view of future environmental and biological impacts. In this study, the conditions under which spherical colloidal crystals (photonic balls) formed mainly of sub-micron-sized monodispersed silica fine particles and carbon black exhibit vivid structural coloring were systematically investigated. The (111) plane of the face-centered cubic colloidal crystal formed by the silica particles is mainly oriented on the surface of the photonic balls formed from monodispersed silica particles. As a result, light in a specific wavelength region is reflected from the photonic balls according to the Bragg condition. When silica particles with diameters of 221, 249, and 291 nm are used, the peaks of the Bragg reflections generated from the photonic balls occur at 495, 562, and 647 nm, respectively; each photonic ball exhibits the ability to produce blue, green, and red colors. In particular, when a black background is used, a vivid structural color is observed from each photonic ball, and it is possible to reproduce all colors using the three primary colors of light by changing the mixture ratio of these photonic balls. The introduction of a small amount of carbon black into the photonic balls makes it possible to reproduce the additive color mixture by the three primary colors of light even when the background color is white. We report that safe and nonbleachable coloring materials with controlled nanosized periodic structures and micrometer-sized geometric structures can be developed using three types of photonic balls consisting of safe and inexpensive silica fine particles with/without carbon black.

DOI： 10.1021/acsanm.0c01366

Web of Science

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Papers - TAKEOKA, Yukikazu