Faculty Profiles - TAKEOKA, Yukikazu

Functional polymethacrylate composite elastomer filled with multilayer graphene and silica particles

Asai, F; Seki, T; Takeoka, Y

CARBON TRENDS Vol. 4 2021.7

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

In this work, a three-component composite elastomer consisting of poly(di(ethylene glycol)methyl ether methacrylate) (PMEO2MA), 110 nm spherical silica particles and multilayer graphene (MLG) is fabricated and its various functions brought about by the characteristic morphology formed by silica particles and MLG are clarified. The presence of silica particles greatly improved the dispersibility of MLG in PMEO2MA, allowing more MLG to be filled. The relative dielectric constant (ε) of the composite elastomers can be increased by increasing the amount of MLG while suppressing the increase in dielectric loss tangent (tanδ). The thermal conductivity of the composite elastomer peak in the middle of the increase in MLGs when the silica particles are not filled, whereas the silica particle-filled system is able to fill the MLGs up to a higher volume fraction and shows higher thermal conductivity. The dynamic viscoelasticity analysis of the composite elastomers shows that the filling effect of MLG is more remarkable in the composite elastomer containing 40 vol% silica particles. The loss factor of vibration damping is found to be larger in the 40 vol% SiO2 - 2.8 vol% MLG composite elastomer over a wider frequency range than in the non-MLG samples.

DOI： 10.1016/j.cartre.2021.100064

Voluthe Phase Transition of Gel (1978: Toyoichi Tanaka)

Optical properties of photonic ball consisting of SiO2 colloidal particles Ⅱ

Ohnuki Ryosuke, Yoshioka Shinya, Takeoka Yukikazu, Sakai Miki

Meeting Abstracts of the Physical Society of Japan Vol. 74.1 ( 0 ) page： 3135 - 3135 2019

Angular dependence of reflection in photonic balls

Ryosuke Ohnuki, Shinya Yoshioka, Miki Sakai, Yukikazu Takeoka

Meeting Abstracts of the Physical Society of Japan Vol. 74.2 ( 0 ) page： 2767 - 2767 2019

Optical properties of photonic ball consisting of SiO2 colloidal particles

Ohnuki Ryosuke, Yoshioka Shinya, Takeoka Yukikazu, Sakai Miki, Seki T., Naoi Yui

Meeting Abstracts of the Physical Society of Japan Vol. 73.2 ( 0 ) page： 2558 - 2558 2018

角度依存性のない構造発色性材料

竹岡敬和

科学と工業 Vol. 1 page： 246 - 251 2016

Fusion Materials for Biomimetic Structurally Colored Materials Reviewed

竹岡敬和

Polymer Journal Vol. 47 page： 106 - 113 2015

コロイド粒子集合体と光との相互作用～角膜から学ぶ角度依存性の少ない構造発色性材料の構築～

竹岡敬和

化学と工業 Vol. 68 page： 502 - 504 2015

コロイド粒子集合体と光との相互作用

竹岡敬和

化学と工業 Vol. 印刷中 2015

白い粒子と黒い粒子からカラフルな色をつくる

竹岡敬和

塗装工学 Vol. 50 page： 76 - 83 2015

高分子ゲルの靱性と伸張性の向上～架橋点が自由に動くポリロタキサン架橋剤を用いた柔軟性の高い刺激応答性高分子ゲルの構築とその物性

竹岡敬和

MATERIAL STAGE Vol. 15 page： 1 - 4 2015

白い粒子と黒い粒子からカラフルな色をつくる

竹岡敬和

塗装工学 Vol. 50 page： 76 - 83 2015

青い色を示す鳥の羽を模倣した角度依存性のない構造発色材料 Reviewed

竹岡敬和

日本ゴム協会誌 Vol. 印刷中 2014

クリスチャンセンフィルター効果を利用した刺激に応じて色を変える相分離型発色材料

竹岡敬和

「"自己組織化"がもたらす材料科学の新境地」機能材料 Vol. 33 page： 32 - 37 2013

クリスチャンセンフィルター効果を利用した刺激に応じて色を変える相分離型発色材料

竹岡敬和

機能材料 Vol. 33 page： 32 - 37 2013

ゲル微粒子懸濁溶液が示す角度依存性のない構造色

竹岡敬和

機能材料 Vol. 32 page： 25 - 28 2012

コロイドアモルファス集合体が示す角度依存性のない構造発色

竹岡敬和

化学工業 Vol. 63 page： 57 - 61 2012

ゲル微粒子懸濁溶液が示す角度依存性のない構造色

竹岡敬和

機能材料 Vol. 32 page： 25 - 28 2012

Versatile Self-Assembled Hybrid Systems with Exotic Structures and Unique Functions Reviewed

竹岡敬和

Current Opinion in Colloid & Interface Science Vol. 16 page： 482 - 490 2011

Characteristics of disperse poly(N-isopropylacrylamide) brushes on silicon surfaces by Atom transfer radical polymerization Reviewed

竹岡敬和

Transactions of the Materials Research Society Japan Vol. 35 page： 845 - 848 2010

Recent advances in hydrogels in terms of fast stimuli responsiveness and superior mechanical performance Reviewed

竹岡敬和

Polymer Journal Vol. 42 page： 839 - 851 2010

ゲルの体積相転移

竹岡敬和

高分子 56 page： 26 - 27 2007

デルの体積相転移

竹岡敬和

高分子 56 page： 26 - 27 2007

NAGAYAMA Kuniaki, TAKEOKA Yukikazu

Kobunshi Vol. 56 ( 1 ) page： 26 - 27 2007

Design of novel microactuator made of self-oscillating gel by assembling the microbeads and controlling their crosslinking structures

Sakai T., Kinoshita M., Takeoka Y., Seki T., Yoshida R.

Polymer Preprints, Japan Vol. 55 ( 2 ) page： 4538 - 4539 2006.12

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

We have prepared the self-oscillating polymer and gels composed of poly(N-isopropylacrylamide) in which ruthenium tris(2,2'-bipyridine) (Ru(bpy)3), a catalyst for the Belousov-Zhabotinsky (BZ) reaction, is covalently bonded to the polymer chain. They change the conformation rhythmically and periodically without external stimuli in closed system. In order to investigate crosslinking effect of the polymers, phase transition behaviors of the linear polymer and the nano-gel beads were analyzed by measuring the transmittance and fluorescence intensity. Furthermore, by arraying the gel beads on the substrate surface, we designed the nano-conveyer which enables to transport substances added on the surface with the propagation of chemical waves induced by the BZ reaction. Artificial worm-like gel having gradient structure was also obtained by unidirectional photopolymerization.

Selective surface modification of PNIPA gel surface by imprinting method

Ueda A., Takeoka Y., Seki T.

Polymer Preprints, Japan Vol. 55 ( 2 ) page： 4573 - 4574 2006.12

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

In recent years, the study of the surface properties of gels have become the focus of much interest due to their function similarity to living body and biocompatibility. We think that the establishment of the innovative approach to the method bring a creation of custom-made surface-functionalized gels. In this study, we obtained surface-functionalized gels by an approach to introduce sulfonic acid group to the surface of a gel by molecularly imprinting method (Scheme 1). To elucidate the presence of the sulfonic acid group on the surface of the gel, we attempted the adsorption test of amino-group modified fluorescence microbeads onto the surface of the gel. The microbeads equably adsorbed on the surface of the gel prepared by this method.

Preparation and optical properties of ordered arrays of glucose-responsible submicrogel particles trapped in inverse opal polystyrene

Honda M., Takeoka Y., Seki T., Kataoka K.

Polymer Preprints, Japan Vol. 55 ( 2 ) page： 4583 - 4584 2006.12

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

First, we obtained a closest-packing photonic crystal that acts as a photonic crystal composed of monodisperse silica particles 300 nm in diameter. A styrene monomer containing an initiator was infiltrated into the crystal and was polymerized so as to trap the crystalline structure. The composite film was soaked in HF solution to remove the silica particles completely. Then the resulting inverse opal polystyrene film with interconnecting porous structure could serve as a template to obtain glucose-responsible nanogel particles. We found that the intensity of Bragg diffraction is altered by the existence of glucose due to the swelling of the embedded nanogel particles. Such behavior was dependent on the glucose concentration.

Photomechanical effect of azobenzene liquid crystalline gel impregnated with low molecular weight liquid crystals

Hayata Y., Nagano S., Takeoka Y., Seki T.

Polymer Preprints, Japan Vol. 55 ( 2 ) 2006.12

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

Azobenzene liquid crystalline gels were prepared by photopolymerization in the Isotropic state. The LC gels with porous structure were prepared by the method to infiltrate a monomer mixture into the closest-packing silica colloid crystals at 100°C. The composite film was soaked in HF solution to remove the silica particles completely. Both porous liquid crystalline gels and non-porous gels were impregnated with 5 CB. We confirmed the photo-induced volume change for both LC gel systems. The effect of introduction of porous structure will be discussed.

Design of functional surface by arraying self-oscillationg nano-gel beads

Sakai T., Takeoka Y., Seki T., Yoshida R.

Polymer Preprints, Japan Vol. 55 ( 1 ) 2006.10

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

We have prepared the self-oscillating polymer and gels composed of poly(N-isopropylacrylamide) in which ruthenium tris(2,2′-bipyridine) (Ru(bpy)s), a catalyst for the BelousovZhabotinsky (BZ) reaction, is covalently bonded to the polymer chain. The periodic conformational or swelling-deswelling changes of the polymer and nano-gel beads were measured as the optical transmittance changes of the solution. In order to investigate crosslinking effect of the polymers, phase transition behaviors of the linear polymer and the nano-gel beads were analyzed by measuring the transmittance and fluorescence intensity. Furthermore, by arraying the gel beads on the substrate surface, we designed the nano-conveyer which enables to transport substances added on the surface with the propagation of chemical waves induced by the BZ reaction.

Swelling behavior of polyrotaxane gels exhibiting structural colors

Murayama H., Nagano S., Ito K., Takeoka Y., Seki T.

Polymer Preprints, Japan Vol. 55 ( 1 ) 2006.10

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

A new type of gel called topological gel having mobile cross-links can be obtained by using polyrotaxanes as gel components. In the present study, polyrotaxane gels with inverse opal structures were prepared by templating a colloidal crystal of silica. The preparative conditions such as selection of crosslinking reagent, temperature, solvent are investigated in detail. As the consequence, polyrotaxane gels showing a structural color were obtained. The reflection wavelength was exactly correlated with the degree of swelling.

Preparation of crosslinked azobenzene liquid crystalline polymer films and their direct evaluation by UV-Vis absorption spectrum

Hayata Y., Nagano S., Takeoka Y., Seki T.

Polymer Preprints, Japan Vol. 55 ( 1 ) 2006.10

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

Crosslinked side-chain liquid crystalline polymers films containing azobenzene moieties were prepared by photopolymerization in the liquid crystalline state. Due to the small amount of azobenzene moieties introduced, the liquid crystalline phase transition and photoisomerization behavior of this film could be directly evaluated by UV-Vis absorption spectrum.

Preparation and optical properties of ordered arrays of glucose-responsible nanogel particles trapped in inverse opal polystyrene

Honda M., Takeoka Y., Seki T., Kataoka K.

Polymer Preprints, Japan Vol. 55 ( 1 ) 2006.10

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

First, we obtained a closest-packing photonic crystal that acts as a photonic crystal composed of monodisperse silica particles 300 nm in diameter. A styrene monomer containing an initiator was infiltrated into the crystal and was polymerized so as to trap the crystalline structure, The composite film was soaked in HF solution to remove the silica particles completely. Then the resulting inverse opal polystyrene film with interconnecting porous structure could serve as a template to obtain glucose-responsible nanogel particles. We found that the intensity of Bragg diffraction is altered by the existence of glucose due to the swelling of the embedded nanogel particles. Such behavior was dependent on the glucose concentration.

Patterning of NIPA gel surface by surface imprinting method

Ueda A., Takeoka Y., Seki T.

Polymer Preprints, Japan Vol. 55 ( 1 ) 2006.10

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

We fabricated the patterning of sulfonic acid groups on the surface of NIPA gel by surface imprinting method as following procedures: 1) amino-terminated SAMs was formed onto a silicon substrate. 2) UV light was irradiated on an amino-terminated SAMs through a photomask. 3) a vinyl monomer having sulfonic acid group was electrostatically coupled with the amino group of the SAMs. 4) A gel is prepared on the vinyl monomer modified silicon substrate by free-radical polymerization. We attempted the adsorption test of amino-group modified fluorescence microbeads onto the surface of the gel (figure 2). These results indicate that the surface modified gel membrane with sulfonic acid can be fabricated from this surface molecularly imprinting method.

Design of nano-oscillation using self-oscillating polymer and the analysis of cooperative effects

ゲル微粒子集積体の構築とその光学的挙動

竹岡敬和

ケミカルエンジニアリング (印刷中) 2006

コロイド結晶をテンプレートとした構造色ゲルの作製とセンサーデバイスへの応用

竹岡敬和

ポリマーフロンティア21 (印刷中) 2006

Sakai T., Takeoka Y., Seki T., Yoshida R.

Polymer Preprints, Japan Vol. 54 ( 2 ) page： 4755 - 4756 2005.12

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

We have prepared the self-oscillating polymer and gels composed of poly(N-isopropylacrylamide) in which ruthenium tris(2,2′-bipyridine) (Ru(bpy) 3), a catalyst for the Belousov-Zhabotinsky (BZ) reaction, is covalently bonded to the polymer chain. The periodic conformational or swelling-deswelling changes of the polymer and nano-gel beads were measured as the optical transmittance changes of the solution. In order to investigate crosslinking effect of the polymers, phase transition behaviors of the linear polymer and the nano-gel beads were analyzed by measuring the transmittance and fluorescence intensity. Furthermore, by arraying the gel beads on the substrate surface, we designed the nano-conveyer which enables to transport substances added on the surface with the propagation of chemical waves induced by the BZ reaction.

Synthesis of photo-responsive porous poly(NIPA) gel and evaluation of its optical properties

Matsubara K., Watanabe M., Takeoka Y.

Polymer Preprints, Japan Vol. 54 ( 1 ) 2005.12

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

A thermosensitive inverse-opal-type porous gel having pendant azobenzene groups, prepared by using a closest-packing SiO2 colloidal crystal as a template, can reversibly change its structural color in response to thermo- and photo-stimuli in water. With varying temperature, the peak values, λmax, of the reflection spectra for the porous gel continuously shifted until the gel network expansion reaches a new equilibrium state, because the gel underwent an isotropic volume change. In contrast, upon UV irradiation from the normal to the gel surface, a new λmax possessing a wavelength longer than that in the dark appeared at constant temperatures, accompanied by the photoinduced volume change of the gel. The change in the λmax could be reversed to the original state by exposure to Vis light through a different process of the variation in the λmax upon the UV irradiation. We concluded that the photo-responsive porous gel undergoes a photoinduced bistable volume change by photo-stimuli. This system enables to convert a two-state isomerization model of the azobenzene molecules into the two-state volume and/or lattice constant change of the porous gel having the azobenzene groups.

Surface modification of gel by molecularly imprinting method

Ueda A., Takeoka Y., Seki T.

Polymer Preprints, Japan Vol. 54 ( 1 ) 2005.12

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

We fabricated a surface modified gel membrane by a molecularly imprinting method as following procedures: 1) a number of amino-terminated SAMs were formed onto a glass substrate by CVD method. 2) a vinyl monomer having sulfonic acid group was electrostatically coupled with the amino group of the SAMs. 3) A gel is prepared on the vinyl monomer modified glass substrate by free-radical polymerization. We are planning on observing the surface state of the gel by a contact angle measurement, XPS and a fluorescent maicrobeads adsorption method.

Structural colored gel

Takeoka Y.

Polymer Preprints, Japan Vol. 54 ( 2 ) page： 4702 - 4704 2005.12

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

"Smart" porous gels with different optical behaviors were synthesized by quantitative adjustment of the cross-linker in pre-gel solutions. A periodically ordered interconnecting porous structure could be created in the gels by using a closest-packing silica colloidal crystal as a template. The interconnecting porosity provides fast response to changes in temperature through the reversible swelling and shrinking of the gels, while the periodically ordered mesoscopic structure endows the porous gels with structural color, which can be tuned by simply changing the amount of the cross-linker in the pre-gel solutions.

Proposal of multicolor electrochromic polymer gels

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

Polymer Preprints, Japan Vol. 54 ( 2 ) page： 4709 - 4710 2005.12

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

Periodically ordered macroporous gels having ionized groups, which can exhibit a monochromatic structural color and undergo a drastic change in the color in response to external stimuli, were prepared by thermally induced radical copolymerization of N-isopropylacrylamide (NIPA) and methacrylic acid (MAAc) using a close-packed silica colloidal crystal as a template. The temperature and pH sensitive optical properties were investigated by reflection spectroscopy. Furthermore, we demonstrated that such pH sensitive optical properties could be manipulated by local pH change induced by water electrolysis. In other words, the electrochromism resulting from the change in structural color was successfully achieved. It was also explored that multicolor electrochromism of the porous gel could be actualized by temperature control of the solution together with the application of sufficient voltage. Moreover, the dynamic optical properties were investigated by the analysis of the diffraction peaks and the actual observation of the volume change behavior. The optical dynamics was critically influenced by the volume change anisotropy of the porous gels.

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.

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.

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

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

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

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

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

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

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

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

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

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

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

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

Optical Characterization of the Photonic Ball as a Structurally Colored Pigment Reviewed International journal

Ryosuke Ohnuki, Miki Sakai, Yukikazu Takeoka, Shinya Yoshioka

LANGMUIR Vol. 36 ( 20 ) page： 5579 - 5587 2020.5

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

A photonic ball is a spherical colloidal crystal. Because it can exhibit vivid structural colors, many attempts have been made to apply it as a structurally colored pigment. However, the optical properties of the photonic ball are complicated because different crystal planes can be involved in the coloration mechanism, depending on the size of the constituent colloidal particles. In this paper, we report a comparative study of photonic balls consisting of silica particles with sizes ranging from 220 to 500 nm. We first analyze the reflectance spectra acquired in a nearly backscattering geometry and confirm that Bragg diffraction from different crystal planes causes several spectral peaks. Second, the angular dependence of reflection is experimentally characterized and theoretically analyzed with appropriate models. These analyses and a comparison with a planar colloidal crystal reveal that the spherical shape plays an essential role in the minor iridescence of photonic balls. We finally discuss a method to enhance color saturation by incorporating small light-absorbing particles. We also discuss the iridescence of the photonic ball under directional and ambient illumination conditions.

DOI： 10.1021/acs.langmuir.0c00736

Highly Transparent and Tough Filler Composite Elastomer Inspired by the Cornea Reviewed International journal

Kenta Watanabe, Eiji Miwa, Fumio Asai, Takahiro Seki, Kenji Urayama, Tomotaka Nakatani, So Fujinami, Taiki Hoshino, Masaki Takata, Chang Liu, Koichi Mayumi, Kohzo Ito, Yukikazu Takeoka

ACS MATERIALS LETTERS Vol. 2 ( 4 ) page： 325 - 330 2020.4

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

We propose a strategy to develop a colorless, transparent, and tough composite elastomer inspired by the cornea, which is the transparent front portion of the eyeball. The composite elastomer, in which 34 vol % hard silica particles with a uniform particle size are dispersed as a filler in a low-crosslinking polymer network exhibits a fracture energy that is similar to 13.5 times higher than that of a system without the silica particles. This strategy also makes the elastomer optically transparent, because the light scattered by each silica particle that forms an ordered structure in the polymer network is cancelled by interference. This research may pave the way for the development of optically transparent and durable materials for applications such as advanced medical devices and soft robots.

DOI： 10.1021/acsmaterialslett.9b00520

Improvement of mechanical properties of elastic materials by chemical methods International journal

Yukikazu Takeoka, Sizhe Liu, Fumio Asai

SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS Vol. 21 ( 1 ) page： 817 - 833 2020.2

Language：English Publishing type：Research paper (scientific journal) Publisher：TAYLOR & FRANCIS LTD

Elastomers such as gels and rubbers play various roles in our lives. Elastomers, which guarantee the safety of airplanes and automobiles and the stability of buildings, are materials that have made the lives of people in the twentieth century extremely convenient. The existence of macromolecules, that is, giant molecules, has been clarified; the development of synthetic macromolecules has progressed; and understanding of elastomers has progressed. By introducing new ideas, it has become possible to obtain tough and hard elastomers, which was difficult under conventional ideas. In this paper, we will explain the development from the classical theory of elastomers to current efforts.

DOI： 10.1080/14686996.2020.1849931

Precise Synthesis of a Homogeneous Thermoresponsive Polymer Network Composed of Four-Branched Star Polymers with a Narrow Molecular Weight Distribution Reviewed International journal

Yuumi Okaya, Yuto Jochi, Takahiro Seki, Kotaro Satoh, Masami Kamigaito, Taiki Hoshino, Tomotaka Nakatani, So Fujinami, Masaki Takata, Yukikazu Takeoka

Macromolecules Vol. 53 ( 1 ) page： 374 - 386 2020.1

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

In this study, the synthesis of a star-shaped polymer with a narrow molecular weight distribution and subsequent formation of a homogeneous polymer network composed of the star-shaped polymer were realized by combining single-electron transfer living radical polymerization, click reaction, and amide bond formation with a condensing agent, which are toolized reactions. First, a 4-armed star polymer consisting of N-isopropylacrylamide was synthesized by living radical polymerization using N,N'-ethylenebis (2,2-dichloroacetamide) as a 4-branched initiator. By this polymerization method, a terminal Cl 4-branched star poly(N-isopropylacrylamide) (PNIPA) with a narrow molecular weight distribution could be obtained, but it was found that the reaction activity of the polymer terminal was lost in the process of purification and isolation. Therefore, after obtaining the terminal Cl 4-branched star PNIPA by living radical polymerization, an azide reaction was carried out in one pot without purification and isolation of the star-shaped polymer. As a result, the azide group was successfully introduced to all ends of the star-shaped polymer. By introducing a carboxyl group or an amino group into the 4-branched star polymer with azide groups using a click reaction, two types of 4-branched star polymers with different end groups were obtained. Equal amounts of both 4-branched star polymers were mixed at a polymer concentration equal to or higher than the overlapping concentration, and as a result of forming an amide bond with a condensing agent, a polymer gel was obtained. The swelling behaviors of the polymer gel indicate that almost no unreacted carboxyl group or amino group was present in the obtained polymer gel. That is, it was found that both 4-branched star polymers reacted efficiently to form a polymer network. In addition, structural observation of the polymer network by the small-angle X-ray scattering method showed that a polymer gel consisting of a network of uniform size was obtained. As mentioned above, we succeeded in constructing a polymer gel consisting of a homogeneous network structure using a temperature responsive 4-branched star polymer as the building block. The living radical polymerization method, the click reaction, and the amide formation by condensation reaction used in this study can be applied not only to the NIPA used here but also to various other monomers. If the construction of a precise network structure is realized by many polymers and the relation with the functional expression derived from the structure is clarified, it will be possible to design the network structure in accordance with the usage of the polymer gel.

DOI： 10.1021/acs.macromol.9b01616

Characterization of Colloidal Amorphous Arrays Prepared by Uniaxial Pressure Application Reviewed International journal

Yui Naoi, Takahiro Seki, Ryosuke Ohnuki, Shinya Yoshioka, Yukikazu Takeoka

LANGMUIR Vol. 35 ( 43 ) page： 13983 - 13990 2019.10

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

We prepared a colloidal amorphous array by applying uniaxial pressure to a powder of monodispersed colloidal silica particles. Pellet-shaped samples were obtained that exhibit different structural colors depending on the diameter of the particles. We characterized the optical properties of the arrays by measuring the angle-dependent scattering spectrum wherein several spectral peaks were observed. The peak at the longest wavelength was caused by the short-range order of the particle arrangement. Interestingly, this peak exhibited a smaller shift in wavelength than that observed in similar samples prepared by several different methods. The other spectral peaks were thought to originate from Mie scattering, which produces a color when the diameter of the colloidal particles is appropriately chosen. Our results showed that uniaxial pressure application can be a suitable method to prepare structurally colored pigments with low angle dependence.

DOI： 10.1021/acs.langmuir.9b02622

Colorful Photonic Pigments Prepared by Using Safe Black and White Materials Reviewed International journal

Miki Sakai, Takahiro Seki, Yukikazu Takeoka

ACS SUSTAINABLE CHEMISTRY & ENGINEERING Vol. 7 ( 17 ) page： 14933 - 14940 2019.9

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

The methods used to prepare vivid color materials that have supported our rich lifestyle are due for review, with the goal of using chemical substances that minimize the significant adverse effects on human health and the environment. In this research, we found that pigments of various colors can be obtained by utilizing submicron-sized amorphous silica fine particles and a complex of iron and tannic acid (Fe-TA complex), which are used for foods, cosmetics, etc. Silica fine particles with uniform submicron particle size appear as a white powder. When silica fine particles form spherical colloidal crystals with short-range order, long-distance order, and periodicity or form colloidal amorphous arrays with only short-range order, the fine particle arrays strongly scatter light with a specific wavelength in all directions. If the wavelength is in the visible light region, these arrays can be used as color materials displaying colors with low angle dependence. However, such arrays formed only from silica fine particles can appear whitish when observed with the naked eye because of noncoherent multiple scattering of light from the interior. Introducing a black Fe-TA complex inside the arrays reduces the effect of the noncoherent multiple scattering of light, and the arrays exhibit bright colors. Safe and inexpensive pigments exhibiting various hues and saturations can be obtained by controlling the size of the silica fine particles, the form of the fine particle arrays, and the incorporated state of the Fe-TA complex. By including TA, the mechanical stability of fine particle arrays and their adhesion to glass substrates are improved, and therefore, the fine particle arrays can be used as coating films.

DOI： 10.1021/acssuschemeng.9b03165

Development of angle-independent color material using colloidal amorphous array Reviewed International journal

Yui Naoi, Takahiro Seki, Shinya Yoshioka, Yukikazu Takeoka

MOLECULAR CRYSTALS AND LIQUID CRYSTALS Vol. 688 ( 1 ) page： 105 - 113 2019.7

Language：English Publishing type：Research paper (scientific journal) Publisher：TAYLOR & FRANCIS LTD

Color materials utilizing physical phenomena such as scattering, diffraction, and interference of light have drawn attention as alternatives to organic dyes that fade by light and some inorganic pigments that are highly toxic. For example, a color material exhibiting structural color caused by a fine structure with a size that is on the order of the wavelength can be prepared using only human body or environmentally friendly materials. If the fine structure is kept stable, the structural colored material can be a nonfading color material. We know that a conventional structural colored material exhibits a property that the hue greatly changes depending on the light irradiation direction and the viewing direction. Recent studies have shown that colloidal amorphous arrays obtained with spherical colloidal particle aggregates with short-range order have almost no angle dependence of the hue under natural light where light is irradiated from all directions. However, the structural color generated from the colloidal amorphous array exhibits angle dependence on the hue under the condition that light is irradiated only from one direction. In this study, we found a light scattering peak, in the scattering spectrum observed from the colloidal amorphous array, showing no angle dependence at all on the shorter wavelength side than the light scattering peak caused by the existence of the short-range order. By exploiting this scattering phenomenon, we will explain the possibility of producing a color material with no angle dependence on the hue even under the condition that light is irradiated only from one direction.

DOI： 10.1080/15421406.2019.1651075

Grating Diffraction or Bragg Diffraction? Coloration Mechanisms of the Photonic Ball Reviewed International journal

Ryosuke Ohnuki, Shinji Isoda, Miki Sakai, Yukikazu Takeoka, Shinya Yoshioka

ADVANCED OPTICAL MATERIALS Vol. 7 ( 13 ) 2019.7

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-V C H VERLAG GMBH

The coloration mechanism of the photonic ball is investigated, which is a spherical aggregation of submicrometer-sized colloidal particles. An interesting optical property is reported for photonic balls with colloidal particles larger than 400 nm: a ring-like iridescent reflection appears on the peripheral part of the ball when observed under an optical microscope. Previous studies considered grating diffraction or Bragg diffraction separately to explain this iridescence. Here, it is shown from detailed structural and optical investigations that both diffraction mechanisms are important. In particular, Bragg diffraction explains the presence of a specific color for the photonic ball when observed with the naked eye in contrast to the iridescence seen under the microscope. The essential idea of the optical analysis is to combine the Bragg diffraction that occurs in the 3D periodic structure with the grating diffraction that originates from the surface with a 2D periodicity. The macroscopic color is almost independent of the angle of observation because of this unique reflection mechanism; hence, the photonic ball can be a suitable candidate for the structurally colored pigment.

DOI： 10.1002/adom.201900227

Optically transparent, high-toughness elastomer using a polyrotaxane cross-linker as a molecular pulley Reviewed International journal

Hiroaki Gotoh, Chang Liu, Abu Bin Imran, Mitsuo Hara, Takahiro Seki, Koichi Mayumi, Kohzo Ito, Yukikazu Takeoka

SCIENCE ADVANCES Vol. 4 ( 10 ) page： eaat7629 2018.10

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER ASSOC ADVANCEMENT SCIENCE

An elastomer is a three-dimensional network with a cross-linked polymer chain that undergoes large deformation with a small external force and returns to its original state when the external force is removed. Because of this hyperelasticity, elastomers are regarded as one of the best candidates for the matrix material of soft robots. However, the comprehensive performance required of matrix materials is a special challenge because improvement of some matrix properties often causes the deterioration of others. For example, an improvement in toughness can be realized by adding a large amount of filler to an elastomer, but to the impairment of optical transparency. Therefore, to produce an elastomer exhibiting optimum properties suitable for the desired purpose, very elaborate, complicated materials are often devised. Here, we have succeeded in creating an optically transparent, easily fabricated elastomer with good extensibility and high toughness by using a polyrotaxane (PR) composed of cyclic molecules and a linear polymer as a cross-linking agent. In general, elastomers having conventional cross-linked structures are susceptible to breakage as a result of loss of extensibility at high cross-linking density. We found that the toughness of the transparent elastomer prepared using the PR cross-linking agent is enhanced along with its Young's modulus as cross-linking density is increased.

DOI： 10.1126/sciadv.aat7629

Spontaneous synthesis of a homogeneous thermoresponsive polymer network composed of polymers with a narrow molecular weight distribution

Jochi Yuto, Seki Takahiro, Soejima Takamasa, Satoh Kotaro, Kamigaito Masami, Takeoka Yukikazu

NPG ASIA MATERIALS Vol. 10 page： 840-848 2018.8

Bioinspired Color Materials Combining Structural, Dye, and Background Colors

Sakai Miki, Seki Takahiro, Takeoka Yukikazu

SMALL Vol. 14 ( 30 ) 2018.7

Spontaneous Preparation of Monodispersed, Structural Colored, Spherical Particles by Rotational Stirring

Teshima Midori, Suzuki Motoki, Seki Takahiro, Takeoka Yukikazu

CHEMNANOMAT Vol. 4 ( 7 ) page： 621-625 2018.7

Environment and human friendly colored materials prepared using black and white components

Takeoka Yukikazu

CHEMICAL COMMUNICATIONS Vol. 54 ( 39 ) page： 4905-4914 2018.5

Structural Coloration of a Colloidal Amorphous Array is Intensified by Carbon Nanolayers

Takeoka Yukikazu, Iwata Masanori, Seki Takahiro, Nueangnoraj Khanin, Nishihara Hirotomo, Yoshioka Shinya

LANGMUIR Vol. 34 ( 14 ) page： 4282-4288 2018.4

Angle-independent structural colored materials by black and white components

Takeoka Yukikazu

ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY Vol. 255 page： . 2018.3

Preparation of angle-independent color materials by applying Mie resonances

Naoi Yui, Takeoka Yukikazu, Seki Takahiro

ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY Vol. 255 page： . 2018.3

Simple preparation of magnetic field-responsive structural colored Janus particles

Teshima Midori, Seki Takahiro, Takeoka Yukikazu

CHEMICAL COMMUNICATIONS Vol. 54 ( 21 ) page： 2607-2610 2018.3

Angle-independent structural colored materials by black and white components Reviewed

Yukikazu Takeoka

ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY Vol. 255 page： . 2018.3

Preparation of angle-independent color materials by applying Mie resonances Reviewed

Yui Naoi, Yukikazu Takeoka, Takahiro Seki

ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY Vol. 255 page： . 2018.3

Structurally colored coating films with tunable iridescence fabricated via cathodic electrophoretic deposition of silica particles Reviewed International journal

Kiyofumi Katagiri, Kensuke Uemura, Ryo Uesugi, Kei Inumaru, Takahiro Seki, Yukikazu Takeoka

RSC ADVANCES Vol. 8 ( 20 ) page： 10776 - 10784 2018

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

In recent years, colloidal arrays of submicrometer-sized monodisperse particles used as structurally colored coatings have drawn great attention due to their non-bleaching properties and low impact on human health and the environment. In this paper, structurally colored coating films were fabricated using monodisperse SiO2 particles via the cathodic electrophoretic deposition (EPD) technique. The addition of a strong polycation, poly(diallyldimethylammonium chloride) (PDDA), enables the cathodic EPD of SiO2 particles and carbon black (CB) additives. Optimizing the quantities of PDDA and CB results in the appearance of vivid structural color from the coating films. The arrangement of the particle array is controllable by varying the pH of the water added to the coating sols for EPD. Structurally colored coating films with and without iridescence, i.e., angular dependence, can be fabricated on demand by a simple operation of the EPD process. In addition, the coating film prepared by cathodic EPD displayed high abrasion resistance because PDDA acts not only as a charge control agent but also as a binder.

DOI： 10.1039/c8ra01215f

白と黒の材料から作られるカラフルな色材:—鮮やかな構造色の発現には，微細構造と黒色物質の存在が重要—

Angle-independent colored materials based on the Christiansen effect using phase-separated polymer membranes

Takeoka Yukikazu

POLYMER JOURNAL Vol. 49 ( 3 ) page： 301-308 2017.3

Highly Responsive Hydrogel out of Poly(N-isopropyl acryalamide) Grafted Polyrotaxane as Building Block Designed by Living Radical polymerization and Click Chemistry Reviewed

Yasumoto, A., Gotoh, H., Gotoh, Y., Imran, A. B., Seki, T., Sakai, Y., Ito, K., Takeoka, Y.

Macromolecules Vol. 50 page： 364-374 2017

Structural color coating films composed of an amorphous array of colloidal particles via electrophoretic deposition Reviewed

Katagiri, K.,* Tanaka, Y., Uemura K., Inumaru, K., Seki, T., Takeoka, Y.

NPG Asia Materials Vol. 9 page： e355 2017

Bio-inspired Bright Structurally Coloured Colored Colloidal Amorphous Array Enhanced by Controlling Thickness and Black Background Reviewed

Ogawa, K., Hara, M., Nagano, S., Seki, T., Takeoka, Y.

Advanced Materials Vol. 29 page： 1605050(1-8) 2017

Photo-tunable Christiansen Colour Filter Using Photoisomerization of Stilbene Reviewed

Ogawa, K., Hara, M., Nagano, S., Seki, T., Takeoka, Y.

Chem. Lett. Vol. 46 page： 1386-1389 2017

竹岡敬和

化学と教育 Vol. 65 ( 12 ) page： 640-643 - 643 2017

Language：English Publishing type：Research paper (scientific journal) Publisher：公益社団法人日本化学会

自然界には，大きく分けて二種類の発色方法がある。染料や顔料を用いた発色と，光の波長サイズの微細構造を利用した発色である。人類は，多くの染料や顔料を自然界から集め，それを人工的に作る方法を身につけてきた。そのおかげで，現在の我々の生活は様々な色にあふれた豊かな環境にある。しかし，21世紀になってからは，人間や環境に対して，より負荷の低い安全な素材を用いた，高耐久性，高機能性を有する色材が求められるようになり，微細構造を利用した発色材料，つまり，構造発色性材料が注目されている。本稿では，自然にある構造発色性材料を取り上げ，これまでにあまり理解されていなかった構造発色性について説明する。

DOI： 10.20665/kakyoshi.65.12_640

Various Structural Colored Pigments Prepared by White and Black Fine Particles

TAKEOKA Yukikazu

Journal of the Japan Society of Colour Material Vol. 90 ( 11 ) page： 393-397 - 397 2017

Language：English Publishing type：Research paper (scientific journal) Publisher：Japan Society of Colour Material

Because safety to the environment and people is respected, safe and inexpensive non-fading colored materials are required. In this review, I will explain how to prepare a material displaying a vivid structural color by using a fine structure that is a comparable to the wavelength size of visible light and a black substance.

DOI： 10.4011/shikizai.90.393

Preparation of Structural Coloring Material using Functional Black Substance

Molecular Weight Dependency of Polyrotaxane-cross-linked Polymer Gel Extensibility Reviewed

Ohmori, K., Imran, A. B., Seki, T., Liu, C., Mayumi, K., Ito, K., Takeoka, Y.

Chemical Communications Vol. 52 page： 13757-13759 2016

TAKEOKA Yukikazu

Hosokawa Powder Technology Foundation ANNUAL REPORT Vol. 24 ( 0 ) page： 66-69 - 69 2016

Language：English Publishing type：Research paper (scientific journal) Publisher：Hosokawa Powder Technology Foundation

Generally, we have an image that the structural colored material changes its hue depending on the direction of light irradiation and the viewing direction. I found that structural colored materials of various hues without angle dependence could be prepared from white and black materials. As a material, silica, titanium oxide, magnetite, and polymers can be used. We can obtain non-toxic and non-fading color materials at low cost using our materials, because the structural colored materials are composed of environment and people-friendly inexpensive materials. Moreover, because black materials exhibiting various functions such as conductivity, magnetic properties, photo-responsiveness, etc., functional colored materials utilizing these functions may be obtained.

DOI： 10.14356/hptf.14110

Molecular weight dependency of polyrotaxane-cross-linked polymer gel extensibility Reviewed

Kana Ohmori, Imran Abu Bin, Takahiro Seki, Chang Liu, Koichi Mayumi, Kohzo Ito, Yukikazu Takeoka

CHEMICAL COMMUNICATIONS Vol. 52 ( 95 ) page： 13757 - 13759 2016

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

This work investigates the influence of the molecular weight of polyrotaxane (PR) cross-linkers on the extensibility of polymer gels. The polymer gels, which were prepared using PR cross-linkers of three different molecular weights but the same number of cross-linking points per unit volume of gel, have almost the same Young's modulus. By contrast, the extensibility and rupture strength of the polymer gels are substantially increased with increasing molecular weight of the PR cross-linker.

DOI： 10.1039/c6cc07641f

Stimulus-responsive colored materials for sensing and display devices

Yukikazu Takeoka

Springer Series in Materials Science Vol. 229 page： 33 - 50 2016

Language：English Publishing type：Part of collection (book) Publisher：Springer Verlag

In this chapter, two types of angle-independent colored systems are described that are achieved without using dyes and pigments: one is a colloidal amorphous array composed of fine colloidal particles, and the other is a phase-separated colored material based on the Christiansen effect. Stimuli-responsive systems using these materials are also introduced.

DOI： 10.1007/978-3-319-24990-2_2

Thermally Tunable Hydrogels Displaying Angle-Independent Structural Colors Reviewed

Yumiko Ohtsuka, Takahiro Seki, Yukikazu Takeoka

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Vol. 54 ( 51 ) page： 15368 - 15373 2015.12

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-V C H VERLAG GMBH

We report the preparation of thermally tunable hydrogels displaying angle-independent structural colors. The porous structures were formed with short-range order using colloidal amorphous array templates and a small amount of carbon black (CB). The resultant porous hydrogels prepared using colloidal amorphous arrays without CB appeared white, whereas the hydrogels with CB revealed bright structural colors. The brightly colored hydrogels rapidly changed hues in a reversible manner, and the hues varied widely depending on the water temperature. Moreover, the structural colors were angle-independent under diffusive lighting because of the isotropic nanostructure generated from the colloidal amorphous arrays.

DOI： 10.1002/anie.201507503

Thermally Tunable Angle-independent Structurally Coloured Hydrogels Reviewed

Ohtsuka, Y., Seki, T., Takeoka, Y

Angew. Chem. Int. Ed. page： in press 2015.12

Thermally Tunable Angle-independent Structurally Coloured Hydrogels Reviewed

Ohtsuka, Y, Seki, T, Takeoka, Y

Angew. Chem. Int. Ed. page： in press 2015.12

Making colors from black and white

Takeoka Yukikazu

ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY Vol. 250 page： . 2015.8

Making colors from black and white Reviewed

Yukikazu Takeoka

ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY Vol. 250 page： . 2015.8

Fusion materials for biomimetic structurally colored materials Reviewed

Yukikazu Takeoka

POLYMER JOURNAL Vol. 47 ( 2 ) page： 106 - 113 2015.2

Language：English Publishing type：Research paper (scientific journal) Publisher：NATURE PUBLISHING GROUP

This review addresses recent developments in structurally colored materials composed of submicrometer-sized fine particles, where the structural color is not angle-dependent. Recently, studies on colloidal crystals of submicrometer-sized fine particles for structurally colored materials applications have drawn great attention. Materials researchers have become aware that many living things exhibit bright structural colors that arise from amorphous arrays of particles, pores and fibers, and are now engaged in research related to this phenomenon. In particular, colloidal amorphous arrays composed of submicrometer-sized fine particles, which can display vivid structural color without angle dependence, have become a popular topic of study within recent years. In this paper, I review the possibility of using colloidal amorphous arrays as stimuli-responsive colored materials based on the properties of colloidal amorphous arrays that have been elucidated in recent experimental investigations.

DOI： 10.1038/pj.2014.125

Facile morphological control of fluorescent nano/microstructures via self-assembly and phase separation of trigonal azobenzenes showing aggregation-induced emission enhancement in polymer matrices

Preparation of Structurally Colored, Monodisperse Spherical Assemblies Composed of Black and White Colloidal Particles using a Micro Flow-Focusing Device Reviewed

Midori Teshima, Takahiro Seki, Ryuji Kawano, Shoji Takeuchi, Shinya Yoshioka, Yukikazu Takeoka

J. Materials Chemistry C, Vol. 3 page： 769-777 2015

Fusion Materials for Biomimetic Structurally Colored Materials Invited Reviewed

Y. Takeoka

Polymer Journal Vol. 47 page： 106-113 2015

Facile morphological control of fluorescent nano/microstructures via self-assembly and phase separation of trigonal azobenzenes showing aggregation-induced emission enhancement in polymer matrices Reviewed

Han, M., Takeoka, Y., Seki, T.

J. Materials Chemistry C, Vol. 3 page： 4093-4098 2015

Han Mina, Takeoka Yukikazu, Seki Takahiro

JOURNAL OF MATERIALS CHEMISTRY C Vol. 3 ( 16 ) page： 4093-4098 2015

Preparation of structurally colored, monodisperse spherical assemblies composed of black and white colloidal particles using a micro-flow-focusing device Reviewed

Midori Teshima, Takahiro Seki, Ryuji Kawano, Shoji Takeuchi, Shinya Yoshioka, Yukikazu Takeoka

JOURNAL OF MATERIALS CHEMISTRY C Vol. 3 ( 4 ) page： 769 - 777 2015

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

It is very annoying when colors fade over time from exposure to bright light. A structurally colored material is a strong candidate for the fabrication of non-fading colored materials composed of environmentally friendly and non-toxic chemicals. We demonstrate that by using a micro-flow-focusing device, monodisperse spherical assemblies displaying various structural colors in air can be prepared from a suspension containing environmentally friendly white and black colloidal particles: monodisperse submicron-sized SiO2 colloidal particles and black magnetite colloidal particles. The average size of the monodisperse spherical assemblies can be controlled by changing the amount of SiO2 colloidal particles used in the preparation of the suspension. The hue of the monodisperse spherical assemblies can be varied by simply altering the size of the SiO2 colloidal particles. These monodisperse spherical assemblies exhibit either iridescent or non-iridescent structural colors, depending on the aggregation state of the SiO2 colloidal particles, which can be controlled by the presence or absence of an electrolyte. Moreover, the saturation of the colors produced by the monodisperse spherical assemblies can be altered by modifying the amount of magnetite colloidal particles that is added. Our results should offer new possibilities for structurally colored materials for future application in pigments and test agents.

DOI： 10.1039/c4tc01929f

Extremely stretchable thermosensitive hydrogels by introducing slide-ring polyrotaxane cross-linkers and ionic groups into the polymer network Reviewed International journal

Abu Bin Imran, Kenta Esaki, Hiroaki Gotoh, Takahiro Seki, Kohzo Ito, Yasuhiro Sakai, Yukikazu Takeoka

NATURE COMMUNICATIONS Vol. 5 page： 5124 2014.10

Language：English Publishing type：Research paper (scientific journal) Publisher：NATURE PUBLISHING GROUP

Stimuli-sensitive hydrogels changing their volumes and shapes in response to various stimulations have potential applications in multiple fields. However, these hydrogels have not yet been commercialized due to some problems that need to be overcome. One of the most significant problems is that conventional stimuli-sensitive hydrogels are usually brittle. Here we prepare extremely stretchable thermosensitive hydrogels with good toughness by using polyrotaxane derivatives composed of alpha-cyclodextrin and polyethylene glycol as cross-linkers and introducing ionic groups into the polymer network. The ionic groups help the polyrotaxane cross-linkers to become well extended in the polymer network. The resulting hydrogels are surprisingly stretchable and tough because the cross-linked alpha-cyclodextrin molecules can move along the polyethylene glycol chains. In addition, the polyrotaxane cross-linkers can be used with a variety of vinyl monomers; the mechanical properties of the wide variety of polymer gels can be improved by using these cross-linkers.

DOI： 10.1038/ncomms6124

Production of Colourful Pigments Consisting of Amorphous Arrays of Silica Particles Reviewed International journal

Shinya Yoshioka, Yukikazu Takeoka

CHEMPHYSCHEM Vol. 15 ( 11 ) page： 2209 - 2215 2014.8

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-V C H VERLAG GMBH

It is desirable to produce colourful pigments that have anti-fading properties and are environmentally friendly. In this Concept, we describe recently developed pigments that exhibit such characteristics. The pigments consist of amorphous arrays of submicron silica particles, and they exhibit saturated and angle-independent structural colours. Variously coloured pigments can be produced by changing the size of the particles, and the saturation of the colour can be controlled by incorporating small amounts of black particles. We review a simple analysis that is useful for interpreting the angular independence of the structural colours and discuss the remaining tasks that must be accomplished for the realistic application of these pigments.

DOI： 10.1002/cphc.201402095

Angle-independent Structural Coloured Materials inspired by Blue Feather Barbs

Colorful-pigment production with amorphous arrays of silica particles Invited Reviewed

S. Yoshioka, Y. Takeoka

ChemPhysChem 2014.6

Light-induced Saturation Change in the Angle-independent Structural Coloration of Colloidal Amorphous Arrays Reviewed

Hirashima, R., Seki, T., Katagiri, K., Akuzawa, Y., Torimoto, T., Takeoka, Y.

J. Materials Chemistry C, Vol. 2 page： 344-348 2014.1

Extremely stretchable thermosensitive hydrogels prepared by introducing polyrotaxane-based slide-ring cross-linkers and ionic groups into the polymer network Reviewed

Abu Bin Imran, Kenta Esaki, Hiroaki Gotoh, Takahiro Seki, Kohzo Ito, Yasuhiro Sakai, Yukikazu Takeoka

Nature Communications Vol. 5 page： 5124:1-8 2014

TAKEOKA Yukikazu

NIPPON GOMU KYOKAISHI Vol. 87 ( 6 ) page： 226-230 - 230 2014

Language：English Publishing type：Research paper (scientific journal) Publisher：THE SOCIRETY OF RUBBER SCIENCE AND TECHNOLOGYY, JAPAN

In this review, I introduce the microstructures and optical properties of angle-independent structurally coloured barbs of blue birds, then describe the fabrication and the optical nature of the artificially prepared imitations of such biological systems.

DOI： 10.2324/gomu.87.226

Light-induced saturation change in the angle-independent structural coloration of colloidal amorphous arrays Reviewed

Ryoko Hirashima, Takahiro Seki, Kiyofumi Katagiri, Yuki Akuzawa, Tsukasa Torimotoa, Yukikazu Takeoka

JOURNAL OF MATERIALS CHEMISTRY C Vol. 2 ( 2 ) page： 344 - 348 2014

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

Light-induced saturation changes in the angle-independent structural coloration of a colloidal amorphous array mainly composed of submicron-sized fine spherical silica particles including a tiny amount of titanium oxide nanoparticles were investigated using a photoelectrochemical reaction of the Ag/Ag+ system, which can exhibit a change in the brightness of the black color.

DOI： 10.1039/c3tc31438c

Structurally Coloured Secondary Particles Composed of Black and White Colloidal Particles Reviewed International journal

Yukikazu Takeoka, Shinya Yoshioka, Midori Teshima, Atsushi Takano, Mohammad Harun-Ur-Rashid, Takahiro Seki

SCIENTIFIC REPORTS Vol. 3 page： 2371 2013.8

Language：English Publishing type：Research paper (scientific journal) Publisher：NATURE PUBLISHING GROUP

This study investigated the colourful secondary particles formed by controlling the aggregation states of colloidal silica particles and the enhancement of the structural colouration of the secondary particles caused by adding black particles. We obtained glossy, partially structurally coloured secondary particles in the absence of NaCl, but matte, whitish secondary particles were obtained in the presence of NaCl. When a small amount of carbon black was incorporated into both types of secondary particles, the incoherent multiple scattering of light from the amorphous region was considerably reduced. However, the peak intensities in the reflection spectra, caused by Bragg reflection and by coherent single wavelength scattering, were only slightly decreased. Consequently, a brighter structural colour of these secondary particles was observed with the naked eye. Furthermore, when magnetite was added as a black particle, the coloured secondary particles could be moved and collected by applying an external magnetic field.

DOI： 10.1038/srep02371

Production of Colored Pigments with Amorphous Arrays of Black and White Colloidal Particles Reviewed

Yukikazu Takeoka, Shinya Yoshioka, Atsushi Takano, Shigeo Arai, Khanin Nueangnoraj, Hirotomo Nishihara, Midori Teshima, Yumiko Ohtsuka, Takahiro Seki

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Vol. 52 ( 28 ) page： 7261 - 7265 2013.7

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-V C H VERLAG GMBH

Sprayed: Pigments with various angle-independent colors were prepared by a spray method (see picture), which is a remarkably simple method using submicrometer-sized silica particles and carbon black. The use of a polyelectrolyte that adheres to the particles can stabilize the structure of the colloidal amorphous arrays to create highly stressable, nonfading pigments. Copyright © 2013 WILEY-VCH Verlag GmbH &amp
Co. KGaA, Weinheim.

DOI： 10.1002/anie.201301321

角度依存性のない構造発色材料 (有機エレクトロニクス)

竹岡敬和

電子情報通信学会技術研究報告 : 信学技報 Vol. 112 ( 410 ) page： 1-5 - 5 2013.1

角度依存性のない構造発色材料

竹岡敬和

電気学会研究会資料. DEI, 誘電・絶縁材料研究会 Vol. 2013 ( 1 ) page： 1-5 - 5 2013.1

Stimuli-Responsive Opals: Colloidal Crystals and Colloidal Amorphous Arrays for Use in Functional Structurally Colored Materials Invited Reviewed

Takeoka, Y.

J. Materials Chemistry C, Vol. 1 page： 6059-6074 2013.1

Producing Coloured Pigments with Amorphous Arrays of Black and White Colloidal Particles Reviewed

Takeoka, Y., Yoshioka, S., Takano, A., Arai, S., Khanin, N., Nishihara, H., Teshima, M., Ohtsuka, Y., Seki, T.

Angew. Chem. Int. Ed. Vol. 52 page： 7261-7265 2013.1

Structurally Coloured Secondary Particles Composed of Black and White Colloidal Particles Reviewed

Takeoka, Y., Yoshioka, S., Teshima, M., Takano, A., Harun-Ur-Rashid, M., Seki, T.

Sci. Rep. Vol. 3 page： 2371-1-7 2013.1

Producing Coloured Pigments with Amorphous Arrays of Black and White Colloidal Particles Reviewed

Takeoka, Y, Yoshioka, S, Takano, A, Arai, S, Khanin, N, Nishihara, H, Teshima, M, Ohtsuka, Y, Seki, T

Angew. Chem. Int. Ed. Vol. 52 page： 7261-7265 2013.1

Applications of Stimuli-Sensitive Inverse Opal Gels

Takeoka Yukikazu

RESPONSIVE PHOTONIC NANOSTRUCTURES: SMART NANOSCALE OPTICAL MATERIALS ( 5 ) page： 150 - 189 2013

Stimuli-responsive opals: colloidal crystals and colloidal amorphous arrays for use in functional structurally colored materials Reviewed

Yukikazu Takeoka

JOURNAL OF MATERIALS CHEMISTRY C Vol. 1 ( 38 ) page： 6059 - 6074 2013

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

Two distinct types of colloidal particle aggregated states exist in opal, namely, the colloidal crystal and the colloidal amorphous array. Today, these aggregates can be artificially prepared and are now studied as non-fading structurally colored materials as a result of our better understanding of their optical properties. Additionally, by applying the aggregates as stimuli-responsive materials, we can fabricate stimuli-responsive structurally colored systems that change their hue and saturation in response to external stimuli. In this review, the conditions necessary for fabricating stimuli-responsive structurally colored systems using the two types of aggregates present in opal are explained.

DOI： 10.1039/c3tc30885e

Angle-independent structural coloured amorphous arrays Reviewed

Yukikazu Takeoka

JOURNAL OF MATERIALS CHEMISTRY Vol. 22 ( 44 ) page： 23299 - 23309 2012.11

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

We are able to observe a colour due to the interference of light from microstructures composed of different refractive index materials that is comparable to the visible wavelength of light; such a colour is called a structural colour. Because structural colour is fadeless and no energy is lost from the colour mechanism, structurally coloured materials are expected to be used for energy-saving reflective displays and sensors. Previously, however, the word "iridescence" rather than "structural colour" was used to describe the property of a surface that appears to change colour as the viewing angle or the angle of light illumination changes. Thus, people who are aware of the concept of interference colour have a strong impression that all structurally coloured materials change hue when viewed from different angles, as indicated by the term "iridescence." In fact, most artificial structurally coloured materials that we and other groups have studied so far change their hue depending on the viewing and light illumination angles because these structural colours are derived from Bragg reflection. Such angle dependence presents a barrier for developing displays and sensors using structurally coloured materials. Therefore, my group has been working to develop angle-independent structural coloured materials. The latest most notable ones are amorphous array systems. In this review, I first introduce the microstructures and optical properties of low-angle-dependent structurally coloured amorphous arrays in biological systems, then describe the fabrication and the optical nature of the artificially prepared imitations of such biological systems, and finally, present the related theoretical studies.

DOI： 10.1039/c2jm33643j

An amorphous array of poly(N-isopropylacrylamide) brush-coated silica particles for thermally tunable angle-independent photonic band gap materials International journal

Yoshie Gotoh, Hiromasa Suzuki, Naomi Kumano, Takahiro Seki, Kiyofumi Katagiri, Yukikazu Takeoka

NEW JOURNAL OF CHEMISTRY Vol. 36 ( 11 ) page： 2171 - 2175 2012.11

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

We precisely prepared thermo-responsive fine core-shell particles consisting of submicron sized silica particles as cores and high-density polymer brushes of thermo-responsive poly(N-isopropylacrylamide) (PNIPA) as shells. The shells were grown by atom transfer radical polymerisation from the initiator that was modified on the surface of the cores. These core-shell particles tend to aggregate in water, even at lower temperatures than the lower critical solution temperature of linear PNIPA. Nevertheless, along with PNIPA in water, changes in the particle size are dependent on water temperature. In accordance with these properties, the amorphous array of the core-shell particles exhibits temperature-reversible changes in the position and the strength of the photonic band gap that does not depend on angle.

DOI： 10.1039/c2nj40368d

Photoinduced Volume Transition in Liquid Crystalline Polymer Gels Swollen by a Nematic Solvent Reviewed

Yuki Hayata, Shusaku Nagano, Yukikazu Takeoka, Takahiro Seki

ACS MACRO LETTERS Vol. 1 ( 11 ) page： 1357 - 1361 2012.11

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

Nematic liquid crystalline (LC) cross-linked polymer gel sheets containing 3 mol % azobenzene (Az) unit were prepared and swollen by a nematic solvent of 4'-pentyl-4-cyanobiphenyl (5CB). This 5CB-swollen gel sheet exhibited a discontinuous volume change around the nematic-isotoropic phase transition temperature of the LC gel (T-NI(G)). UV irradiation at a temperature slightly lower than T-NI(G) provoked a large volume transition (expansion) due to a loss of nematic order within the gel sheet caused by the trans-to-cis photoisomerization of Az. The volume was reverted by irradiation with 436 run light By templating the colloidal crystal film of monodispersed silica particles, a LC gel sheet possessing a microporous structure was also prepared. Due to the facilitated diffusion of 5CB the microporous LC gel exhibited significant enhancements,in the extent and rate of the photoinduced volume transition.

DOI： 10.1021/mz300447j

Angle-independent Structural Coloured Amorphous Arrays

Y. Takeoka

J. Materials Chemistry Vol. 22 page： 23299-23309 2012.4

Angle-independent Structural Coloured Amorphous Arrays

Y. Takeoka

J. Materials Chemistry Vol. 22 page： 23299-23309 2012.4

Fabrication of mono-dispersed spherical assemblies and these structural colors by using microflow device International journal

Midori Teshima, Yukikazu Takeoka, Takahiro Seki, Ryuji Kawano, Shinya Yoshioka, Shoji Takeuchi

Proceedings of the 16th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2012 page： 644 - 646 2012.1

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

Structural colors are caused by the interaction of visible light with micro structures of the substances, on a length scale comparable to optical wavelength. We pay marked attention to the structural colored materials because of these less fading and low environment burden compared with the colored materials using dyes. This report shows that we fabricated monodispersed spherical assembly (MDSA) composed of submicron silica particles as a structural color material by using a micro flow focusing device (MFFD). Moreover, we will introduce the improvement for the coloration of the spherical assembly by magnetic particles.

Versatile self-assembled hybrid systems with exotic structures and unique functions Reviewed

Amorphous Array of Poly(N-isopropylacrylamide) Brush-Coated Silica Particles for Thermally Tunable Angle-Independent Photonic Band Gap Materials

Gotoh, Y., Suzuki, H., Kumano, N., Seki, T., Katagiri, K., Takeoka, Y.

New Journal of Chemistry Vol. 36 page： 2171-2175 2012

Takashi Nakanishi, Masanobu Naito, Yukikazu Takeoka, Kazunori Matsuura

CURRENT OPINION IN COLLOID & INTERFACE SCIENCE Vol. 16 ( 6 ) page： 482 - 490 2011.12

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE LONDON

In this review article, we describe recent progress about exotic self-assembled systems with various dimensions including biomolecules, supramolecules, unique hydrophobic amphiphiles. polymers, nano-clusters. and colloidal particles. Construction of robust biomolecular assemblies with exotic structures, such as ring and hollow capsule, is achieved by rational designs of symmetric biomolecular conjugates. In addition, we comprehensively summarized leading-edge topics on optical/topological properties of self-assembled hybrid systems, such as circularly polarized luminescence or structural color. The preparation of colloidal amorphous array with photonic band gap-induced angle-independent structural color is also achieved in consideration of the following situations: i) two-body sphere-sphere potential, ii) disorder packing using different sizes of colloidal particles, and iii) softness of colloidal particles. Lastly, we demonstrated useful utilizations of exotic self-assembled objects. Flakelike microparticles were transcribed into various nano-flake metals and applied as temperature indicator for the local heating of an addictive. All findings described here show meaningful hybrid strategies in self-assembly techniques and their functionalization as well as materialization. (C) 2011 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.cocis.2011.08.003

Multicolor Polymer-Dispersed Liquid Crystals Reviewed International journal

Naomi Kumano, Takahiro Seki, Masahiko Ishii, Hiroshi Nakamura, Tomonari Umemura, Yukikazu Takeoka

ADVANCED MATERIALS Vol. 23 ( 7 ) page： 884 - + 2011.2

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-BLACKWELL

The potential of a self-assembled phase-separated macroporous polymer film filled with an appropriate solvent for application in a functional multicolor polymer-dispersed liquid crystal (PDLC) display is explored. The findings demonstrate that a phase-separated porous MMAA-BIS polymer network filled with mixed LCs of 5CB and 5PCH can exhibit changes in structural color covering the whole visible region and an opaque milky color upon temperature variation. This system may be available for energy-saving multicolor displays.

DOI： 10.1002/adma.201003660

Precise Synthesis and Physicochemical Properties of High-Density Polymer Brushes designed with Poly(N-isopropylacrylamide) Reviewed

Tunable Angle-Independent Structural Colour from Phase Separated Porous Gel Reviewed

Kumano, N., Seki, T., Ishii, M., Nakamura, H., Takeoka, Y.

Vol. 50 page： 4012-4015 2011

Versatile Self-Assembled Hybrid Systems with Exotic Structures and Unique Functions Invited Reviewed

Nakanishi, T., Naito, M., Takeoka, Y., Matsuura, K.

Current Opinion in Colloid and Interface Science Vol. 16 page： 482-490 2011

Multi-Colour Polymer Dispersed Liquid Crystal Reviewed

Kumano, N., Seki, T., Ishii, M., Nakamura, H., Umemura, T., Takeoka, Y.

Adv. Mater. Vol. 23 page： 884-888 2011

Tunable Angle-Independent Structural Color from a Phase-Separated Porous Gel Reviewed International journal

Naomi Kumano, Takahiro Seki, Masahiko Ishii, Hiroshi Nakamura, Yukikazu Takeoka

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Vol. 50 ( 17 ) page： 4012 - 4015 2011

Hiromasa Suzuki, Huda Muhammad Nurul, Takahiro Seki, Taisuke Kawamoto, Hisashi Haga, Kazushige Kawabata, Yukikazu Takeoka

MACROMOLECULES Vol. 43 ( 23 ) page： 9945 - 9956 2010.12

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

A high-density polymer brush of poly(N-isopropylacrylamide) (PNIPA) was precisely prepared following carefully selected procedures, which included selecting the underlying substrate, preparing its surface, and grafting PNIPA on the substrate. As a result, the graft density and the dried thickness of the brush reached more than 0.5 chains/nm(2) and 200 nm, respectively, for the best combination of each procedure. This high-density polymer brush showed gradual collapse with increasing temperature in water, which must be attributed to both the low swelling and the low shrinking abilities of the brush that result from the physically constrained state of the polymers. The contact angle of the air bubbles underneath the high-density polymer brush also gradually decreased up to around 25 degrees C in water with increasing temperature, which indicates that the hydrophilicity of the surface decreases as it does in typical PNIPA-grafted membranes and gels. Starting at the lower critical solution temperature of free PNIPA in water, approximately 32 degrees C, the value of the contact angle started to increase dramatically, and it became constant when the solution temperature exceeded 40 degrees C. Ultimately, the surface exhibited a mostly hydrophilic nature at higher temperatures. The temperature-dependent contact angles can be interpreted by assuming that the terminally chlorinated alkyl groups of the elongated PNIPAs can be positioned on the surfaces or hidden in the vicinity of the membranes, depending on the temperature of the solution.

DOI： 10.1021/ma101439f

Recent advances in hydrogels in terms of fast stimuli responsiveness and superior mechanical performance

Imran Abu Bin, Seki Takahiro, Takeoka Yukikazu

Polymer journal Vol. 42 ( 11 ) page： 839-851 2010.11

Recent advances in hydrogels in terms of fast stimuli responsiveness and superior mechanical performance

Bin Imran Abu, Seki Takahiro, Takeoka Yukikazu

POLYMER JOURNAL Vol. 42 ( 11 ) page： 839-851 2010.11

Poly(N-isopropylacrylamide) Gel Prepared Using a Hydrophilic Polyrotaxane-Based Movable Cross-Linker Reviewed

Abu Bin Imran, Takahiro Seki, Kohzo Ito, Yukikazu Takeoka

MACROMOLECULES Vol. 43 ( 4 ) page： 1975 - 1980 2010.2

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

A novel type of thermosensitive polymer gel was fabricated using a hydrophilic polyrotaxane as a movable cross-linker and N-isopropylacrylamide (NIPA) as a monomer. An optical transparence, mechanical softness, abnormal swelling capacity, and unprecedentedly fast thermosensitivity are among the salient features of this new polyNIPA gel in comparison with typical polyNIPA gels prepared by bifunctional cross-linker Such as N,N'-methylenebisacrylamide (TN gels) and a previously reported polyNIPA gel using a hydrophobic polyrotaxane as a cross-linker. Whereas TN gels can take more than a day to undergo full deswelling in response to sudden temperature change, Our new gel collapses in similar to 10 min. The hydrophilicity and movability of the cross-linker contribute to these unprecedented properties of this thermosensitive polyNIPA gel. Moreover, this new type of cross-linker can be applied to any of the conventional gels made by radical polymerization and will likely improve the stimuli responses and mechanical properties of the gels.

DOI： 10.1021/ma902349j

Characteristics of High-Density Poly(N-isopropylacrylamide) (PNIPA) Brushes on Silicon Surface by Atom Transfer Radical Polymerization

Angle-Independent Structural Color in Colloidal Amorphous Arrays Reviewed

Mohammad Harun-Ur-Rashid, Abu Bin Imran, Takahiro Seki, Masahiko Ishi, Hiroshi Nakamura, Yukikazu Takeoka

CHEMPHYSCHEM Vol. 11 ( 3 ) page： 579 - 583 2010.2

Angle-Independent Structural Color in Colloidal Amorphous Arrays Reviewed

Harun-Ur-Rashid, M., Imran, A. B., Seki, T., Ishii, M., Nakamura, H., Takeoka, Y.

ChemPhysChem. Vol. 11 page： 579-583 2010

Characteristics of disperse poly(N-isopropylacrylamide) brushes on silicon surfaces by Atom transfer radical polymerization

Huda, M.N., Seki, T., Suzuki, H., Kabir, A.N.M.H., Rashid, H.U., Takeoka, Y.

Transactions of the Materials Research Society Japan Vol. in press. 2010

Hydrophobic and hydrophilic polyrotaxane based movable cross-linkers for thermo-sensitive poly(N-isopropylacrylamide) gels Reviewed

Imran, A. B., Seki, T., Ito, K., Takeoka, Y.

Transactions of the Materials Research Society Japan Vol. in press. 2010

Facile synthesis of sliding poly(NIPA) gels using a vinyl modified polyrotaxane as a Cross-linker Reviewed

Vol. in press. 2010

Poly(N-isopropylacrylamide) gel prepared using a hydrophilic polyrotaxane-based movable cross-linker Reviewed

Imran, A. B., Seki, T., Ito, K., Takeoka, Y.

Macromolecules Vol. 43 page： 1975-1980 2010

Huda M.Nurul, Seki Takahiro, Suzuki Hiromasa, Kabir A.N.M Hamidul, Rashid M. Harunur, Takeoka Yukikazu

Transactions of the Materials Research Society of Japan Vol. 35 ( 4 ) page： 845-848 - 848 2010

Language：English Publishing type：Research paper (scientific journal) Publisher：The Materials Research Society of Japan

High-density poly(N-isopropylacrylamide) (PNIPA) brushes were synthesized on silicon surfaces by surface initiated ATRP at various polymerization conditions. Polymerization was achieved using CuCl/tris(2-(dimethylamino)ethyl)amine (Me6TREN) as a catalytic system in DMSO at 20℃. The linear evolution of number average molecular weight (Mn) versus monomer conversion, the increase in layer thickness with polymerization time and relatively low molecular weight distribution (～ 1.2) indicate a well-controlled manner of polymerization. The average value of grafting density of PNIPA brushes was around 0.48 chain/nm2: We obtained high-density PNIPA brushes. During the measurement of air bubble contact angle under the surface of the PNIPA brushes in water, the surface property of PNIPA brushes shows an interesting phenomenon, which is antithetic to that of typical PNIPA gel. With the increase of temperature from 10℃, the surfaces of the PNIPA brushes gradually change to more hydrophobic natures. But as temperature approaches the LCST, the brush surfaces turned back to hydrophilic state. This might be the effect of the change in the surface morphology of the polymer brushes and/or the change in physical state of the terminal end groups of the polymer, depending on temperature.

DOI： 10.14723/tmrsj.35.845

Hydrophobic and hydrophilic polyrotaxane based movable cross-linkers for thermo-sensitive poly(N-isopropylacrylamide) gels

Imran Abu Bin, Seki Takahiro, Ito Kohzo, Takeoka Yukikazu

Transactions of the Materials Research Society of Japan Vol. 35 ( 2 ) page： 291-297 - 297 2010

Language：English Publishing type：Research paper (scientific journal) Publisher：The Materials Research Society of Japan

A novel hydrogel has been fabricated using vinyl modified polyrotaxane as a cross-linker. A sparsely dispersed propylene oxide modified α-cyclodextrins which were threaded into the long polyethylene glycol (Mw = 35000) and were trapped by bulky 1-adamantanamine molecules was used as a hydrophilic polyrotaxane, HPR. HPR was modified by a small amount 2-acryloyloxyethylisocyanate monomer to obtain a water soluble polyrotaxane-based movable cross-linker, MHPR. Polymer gels, prepared by free radical polymerization of thermo-sensitive monomer N-isopropylacrylamide (NIPA) in presence of MHPR cross-linker, gave transparent, soft and flexible, mechanically strong and fast thermo-sensitive gels. The gel changes its volume isotropically and reaches rapidly to the equilibrium shrunken state after a temperature jump. The hydrophilicity of the cross-linker retains the homogeneity in the gel network and restricts the formation of aggregated globules, which permits the poly(NIPA) chains along with macrocycles to move or rotate freely inside the gel networks under deformation. The movability of the cross-links can strongly minimize their localized stress during deformation. The fascinating characteristics of the gel was compared and contrasted with the gels prepared using using hydrophobic polyrotaxane-based multifunctional and bi-functional N,N'-methylene-bis-acrylamide cross-linkers.

DOI： 10.14723/tmrsj.35.291

Facile synthesis of sliding poly(NIPA) gels using a vinyl modified polyrotaxane as a cross-linker

Bin Imran Abu, Seki Takahiro, Ito Kohzo, Takeoka Yukikazu

Transactions of the Materials Research Society of Japan Vol. 35 ( 4 ) page： 841-844 - 844 2010

Language：English Publishing type：Research paper (scientific journal) Publisher：The Materials Research Society of Japan

A unique hydrogel has been synthesized using supramolecular polyrotaxane as the starting material. Sparsely dispersed α-cyclodextrins threaded into long polyethylene glycol axle (Mw=35000) trapped with a stable capping agent, 1-adamantanamine of polyrotaxane (PR) unit was used for this purpose. The modification of the hydroxyl groups of α-CDs of the PR by a vinyl monomer containing an active isocyanate group at one end resulted in the formation of a stable carbamate bond with hydroxyl groups to give the modified polyrotaxane based cross-linker (MPR). Polymer gels were designed using MPR as a cross-linker and N-isopropylacrylamide, NIPA as a monomer and transparent, very soft, flexible, fast responsive and mechanically improved polymer gels could be obtained. The polymer chains can slide and rotate about the movable cross-linker in the gel network, which potentially improves the properties of the gels over conventional chemically cross-linked polymer gel.

DOI： 10.14723/tmrsj.35.841

Confined Stimuli-Responsive Polymer Gel in Inverse Opal Polymer Membrane for Colorimetric Glucose Sensor Reviewed

Characteristics of disperse poly(N-isopropylacrylamide) brushes on silicon surfaces by Atom transfer radical polymerization

Huda, M.N, Seki, T, Suzuki, H, Kabir, A.N.M.H, Rashid, H.U, Takeoka, Y

Transactions of the Materials Research Society Japan Vol. in press. 2010

Hydrophobic and hydrophilic polyrotaxane based movable cross-linkers for thermo-sensitive poly(N-isopropylacrylamide) gels Reviewed

Imran, A. B, Seki, T, Ito, K, Takeoka, Y

Transactions of the Materials Research Society Japan Vol. in press. 2010

Facile synthesis of sliding poly(NIPA) gels using a vinyl modified polyrotaxane as a Cross-linker Reviewed

Vol. in press. 2010

Masaki Honda, Kazunori Kataoka, Takahiro Seki, Yukikazu Takeoka

LANGMUIR Vol. 25 ( 14 ) page： 8349 - 8356 2009.7

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

We developed a totally synthetic colorimetric glucose-sensing system that is composed of glucose-responsive hydrogel particles confined in all inverse opal polymer membrane. This system exhibits structural color on the basis of Bragg diffraction arising from the 3-D ordered structure with periodicity on the order of the wavelength of visible light. The volume of the hydrogel particles reversibly changes as the glucose concentration varies in the separated pores of the inverse opal polymer membrane; this system reveals a reversible change in the color appearance and the peak intensity of the reflection spectra with the variation in the glucose concentration. By careful design of the system, we can detect the important range of glucose concentration around the threshold value for diagnosing diabetes mellitus by using the colorimetric glucose-sensing system.

DOI： 10.1021/la804262b

Dual Tuning of the Photonic Band-Gap Structure in Soft Photonic Crystals Reviewed International journal

Masaki Honda, Takahiro Seki, Yukikazu Takeoka

ADVANCED MATERIALS Vol. 21 ( 18 ) page： 1801 - + 2009.5

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-V C H VERLAG GMBH

A dually tunable photonic crystal composed of thermosensitive gel particles confined in a pH-sensitive inverse-opal gel is reported. The position of the photonic band-gap can be thermally regulated, while its intensity is dramatically changed by pH. Reversible, independent, and extensive switching of the position and intensity of the photonic band-gap could be achieved using independent external stimuli.

DOI： 10.1002/adma.200801258

Structural Colored Liquid Membrane without Angle Dependence Reviewed International journal

Yukikazu Takeoka, Masaki Honda, Takahiro Seki, Masahiko Ishii, Hiroshi Nakamura

ACS APPLIED MATERIALS & INTERFACES Vol. 1 ( 5 ) page： 982 - 986 2009.5

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

We have demonstrated for the first time that condensed gel particle suspensions in amorphous-like states display structural color with low angle dependence. This finding is in contrast to the common understanding that a periodic dielectric structure is fundamental to photonic band gap (PBG) production, and it validates the theory that a "tight bonding model" that is applicable to semiconductor systems can also be applied to photonic systems. More practically, this structural colored suspension represents a promising new material for the manufacture of reflective full-color displays with a wide viewing angle and nonfading color materials. This liquid system shows promise as a display material because electronic equipment used for display systems can easily be filled with the liquid in the same way that liquid crystals are currently used.

DOI： 10.1021/am900074v

Several Aggregation States Composed of Colloidal Particles: Application to Structural Colored Materials(<Special Issue>The Front Line of Pseudo-Crystalline Structures Formed by Complex Polymers)

Structural Colored Gel Invited Reviewed

Takeoka, Y.

J. Photopolymer Sci. & Tech. Vol. 22 page： 123 - 132 2009

Electrochromism based on structural clour changes in a polyelectrolyte gel Reviewed

Ueno, K., Sakamoto, J., Takeoka, Y. Watanabe, M.

J. Mater. Chem. Vol. 1 page： 4778-4783 2009

Structural Coloured Liquid Membrane without Angle-Dependence Reviewed

Takeoka, Y. Honda, M., Seki, T., Ishii, M., Nakamura, H.

ACS Applied Materials & Interfaces Vol. 1 page： 982-986 2009

Template Synthesis for Stimuli-Responsive Angle Independent Structural ColoredSmart Materials Reviewed

Harun-Ur-Rashid, M., Imran, A. B., Seki, T., Ishii, M., Nakamura, H., Takeoka, Y.

Transactions of the Materials Research Society Japan Vol. in press 2009

Confined Stimuli-Responsive Polymer Gel in Inverse Opal Polymer Membrane for Colorimetric Glucose sensor Reviewed

Honda, M., Kataoka, K., Seki, T., Takeoka, Y.

Langmuir Vol. 25 page： 8349-8356 2009

*Dual Tuning of Photonic Band Gap Structure in Soft Photonic Crystal Reviewed

Honda, M., Seki, T., Takeoka, Y.

Adv. Mater. Vol. 21 page： 1801-1804 2009

Structural Colored Gels for Tunable Soft Photonic Crystals Invited Reviewed

Rashid, H.-u., Seki, T., Takeoka, Y.

The Chemical Record Vol. 9 page： 87-105 2009

Takeoka Yukikazu

Journal of the Japanese Association for Crystal Growth Vol. 36 ( 1 ) page： 49-54 - 54 2009

Language：English Publishing type：Research paper (scientific journal) Publisher：The Japanese Association for Crystal Growth (JACG)

Here, I show the fundamental optical behaviors of aggregation states of colloidal particles: colloidal crystal, colloidal amorphous, and colloidal quasi-crystal.

DOI： 10.19009/jjacg.36.1_49

Electrochromism based on structural colour changes in a polyelectrolyte gel Reviewed International journal

Kazuhide Ueno, Junji Sakamoto, Yukikazu Takeoka, Masayoshi Watanabe

JOURNAL OF MATERIALS CHEMISTRY Vol. 19 ( 27 ) page： 4778 - 4783 2009

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

Electrochromism based on structural colours was demonstrated by employing a simple system composed of a two-electrode cell, a salt-free organic solvent, and a nanostructured electroactive soft material. A polyelectrolyte gel, poly(HEMA-co-MAPTA-PF6), with an inverse-opal structure was prepared by using a polystyrene close-packed colloidal crystal as a template. The resulting gel swollen in binary organic solvents exhibited monochromatic structural colours. The structural colour of the gel was altered over the entire visible light region by changing the solvent polarity. Moreover, the structural colour could be tuned by applying a relatively low voltage, where the change in the lattice constant of the inverse-opal along the gel thickness direction, triggered by an electrodragging force on the polyelectrolyte gel under the electric field, was responsible for the colour change. The present system offers a novel concept for full-colour electrochromic materials, and the system can be tuned to exhibit the full range of colours by using single materials.

DOI： 10.1039/b900261h

Structural Colored Gel

Takeoka Yukikazu

JOURNAL OF PHOTOPOLYMER SCIENCE AND TECHNOLOGY Vol. 22 ( 2 ) page： 123-132 2009

Structural Colored Gel Reviewed

Yukikazu Takeoka

JOURNAL OF PHOTOPOLYMER SCIENCE AND TECHNOLOGY Vol. 22 ( 2 ) page： 123 - 132 2009

Language：English Publishing type：Research paper (scientific journal) Publisher：TECHNICAL ASSOC PHOTOPOLYMERS,JAPAN

A periodically ordered interconnecting porous structure can be embodied in a chemical gel by using a closest-packed colloidal crystal as a template. The interconnecting porosity not only provides a quick response but also endows the porous gel with structural color arising from coherent Bragg optical diffraction. The structural color revealed by porous gels can be regulated by several techniques, and thus it is feasible to obtain desirable, smart, soft materials. The swelling parameter of the polymer chains in the polymer network in response to the environment may be recognized through the variation in the color of the structural colored gel by using the fine colloidal crystal. The role of the volume interactions between the polymer chains in the gel can be estimated by simply measuring the length of the gel, based on the assumption that the subchains in the polymer network under the preparation conditions behave as unperturbed Gaussian coils. This means that it is possible to determine the change at the molecular level in the gel such as the swelling parameter of the polymer chains in the polymer network in response to the environment with the naked eye only when the gel is fabricated from specific a pre-gel solution and a colloidal crystal. The linear expansion factor of the subchains was assessed by comparing the positions of the diffraction peak (lambda(max)) in a given situation and the Gaussian state at temperatures lower than the LCST of the porous gel. The periodically ordered structure with a size corresponding to the wavelength of optical light allows us to detect the behavior of polymer chains through the structural color. This review focuses on the synthesis of the structural colored porous gel and on the visualizing conformations of subchains by creating optical wavelength-sized periodically ordered structure in hydrogel. The main portion of this article was previously published in Langmuir.(19)

DOI： 10.2494/photopolymer.22.123

Structural Colored Gels for Tunable Soft Photonic Crystals Reviewed

Mohammad Harun-Ur-Rashid, Takahiro Seki, Yukikazu Takeoka

CHEMICAL RECORD Vol. 9 ( 2 ) page： 87 - 105 2009

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-V C H VERLAG GMBH

A periodically ordered interconnecting porous structure can be embodied in chemical gels by using closest-packed colloidal crystals as templates. The interconnecting porosity not only provides a quick response but also endows the porous gels with structural color arising from coherent Bragg optical diffraction. The structural colors revealed by porous gels can be regulated by several techniques, and thus, it is feasible to obtain desirable, smart, soft materials. A well-known thermosensitive monomer, N-isopropylacrylamide (NIPA), and other minor monomers were used to fabricate various structural colored gels. The selection of minor monomers depended on the targeted properties. This review focuses on the synthesis of templates, structural colored porous gels, and the applications of structural colored gel as smart soft materials for tunable photonic crystals. (D 2009 The Japan Chemical journal Forum and Wiley Periodicals, Inc. Chem Rec 9: 87-105; 2009: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.20169

DOI： 10.1002/tcr.20169

Template Synthesis for Stimuli-Responsive Angle Independent Structural Colored Smart Materials

Harun-Ur-Rashid Mohammad, Imran Abu Bin, Seki Takahiro, Takeoka Yukikazu, Ishii Masahiko, Nakamura Hiroshi

Transactions of the Materials Research Society of Japan Vol. 34 ( 2 ) page： 333-337 - 337 2009

Language：English Publishing type：Research paper (scientific journal) Publisher：The Materials Research Society of Japan

Like other conventional smart materials, structural color showing smart materials inherit physical and chemical characteristics imposed by the templates. Smart Material such as structural colored gel made of photonic crystal (PC) as template, exhibits angle dependent structural color because the color arises from the Bragg optical diffraction of light from crystal planes. But angle independent or low angle dependent structural color is required for devising of display with a wide viewing angle. To meet this purpose we prepared photonic glass (PG) from silica colloidal spheres. This PG is able to exhibit structural color, which is stable against the change of the angle of view and the angle of illumination. The transmittance spectrum evidences the angle independence of the structural color of PG. The Fast Fourier Transformation and the autocorrelation function prove that we prepared an amorphous material. The existence of short range order helps PG to exhibit angle independent structural color.

DOI： 10.14723/tmrsj.34.333

Template Synthesis for Stimuli-Responsive Angle Independent Structural ColoredSmart Materials Reviewed

Harun-Ur-Rashid, M, Imran, A. B, Seki, T, Ishii, M, Nakamura, H, Takeoka, Y

Transactions of the Materials Research Society Japan Vol. in press 2009

Chromic slide-ring gel based on reflection from photonic bandgap Reviewed

Harumi Murayama, Abu Bin Imran, Shusaku Nagano, Takahiro Seki, Masatoshi Kidowaki, Kohzo Ito, Yukikazu Takeoka

MACROMOLECULES Vol. 41 ( 5 ) page： 1808 - 1814 2008.3

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

Here we report on a chromic slide-ring gel consisting of polyrotaxane by using a close-packed colloidal crystal as a template. In the slide-ring gel, the polymer chains with bulky end groups are not covalently cross-linked like chemical gels nor do they interact attractively like physical gets, but are topologically interlocked by figure-of-eight cross-links. The slide-ring gel has freely movable cross-links, which have a pulley effect on tensile deformation. This effect improves the mechanical properties of polymer gels. In this work, this physically and mechanically optimized polymer gel was used to make stimuli-responsive photonic band gap materials. Our gel exhibits solvatochromic behavior based on the change in structural color.

DOI： 10.1021/ma0715627

Chemical and optical control of peristaltic actuator based on self-oscillating porous gel Reviewed

*Photoregulated Worm-like Motion of Gel Reviewed

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

Angew. Chem. Int. Ed. Vol. 97 page： 9039-9043 2008

*Fabrication of Mechanically Improved Hydrogels Using Movable Cross-linker Based on Vinyl Modified Polyrotaxane Reviewed

Imran, A. B., Seki, T., Kataoka, T., Kidowaki, M., Ito, K., Takeoka, Y.

Chemical Communications page： 5227-5229 2008

Chemical and Optical Control of Peristaltic Actuator Based on Self-Oscillating Porous Gel Reviewed

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

Chemical Communications Vol. 4735-4737 2008

Chromic Slide-Ring Gel based on Reflection from Photonic Bandgap Reviewed

Murayama, H., Imran, A. B., Nagano, S., Seki, T., Kidowaki, M., Ito, K., Takeoka, Y.

Macromolecules Vol. 41 page： 1808-1814 2008

Shu-ichi Shinohara, Takahiro Seki, Takamasa Sakai, Ryo Yoshida, Yukikazu Takeoka

CHEMICAL COMMUNICATIONS Vol. 4735-4737 ( 39 ) page： 4735 - 4737 2008

Photoregulated Wormlike Motion of a Gel Reviewed International journal

Shu-ichi Shinohara, Takahiro Seki, Takamasa Sakai, Ryo Yoshida, Yukikazu Takeoka

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Vol. 47 ( 47 ) page： 9039 - 9043 2008

Fabrication of mechanically improved hydrogels using a movable cross-linker based on vinyl modified polyrotaxane Reviewed International journal

Abu Bin Imran, Takahiro Seki, Toshiyuki Kataoka, Masatoshi Kidowaki, Kohzo Ito, Yukikazu Takeoka

CHEMICAL COMMUNICATIONS ( 41 ) page： 5227 - 5229 2008

Photoregulated wormlike motion of a gel Reviewed

Shinohara Shu-ichi, Seki Takahiro, Sakai Takamasa, Yoshida Ryo, Takeoka Yukikazu

Angewandte Chemie Vol. 120 ( 47 ) page： 9179 2008

An electro- and thermochromic hydrogel as a full-color indicator Reviewed International journal

Kazuhide Ueno, Kazuki Matsubara, Masayoshi Watanabe, Yukikazu Takeoka

ADVANCED MATERIALS Vol. 19 ( 19 ) page： 2807 - + 2007.10

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-V C H VERLAG GMBH

Electric-field-triggered "two-state switching" between two arbitrary structural colors (see figure) in the entire visible region at certain temperatures is shown by a stimuli-responsive chromic hydrogel. The external rapid tuning in the structural color of this hydrogel is successfully achieved by introducing a periodically ordered interconnecting porous structure.

DOI： 10.1002/adma.200700159

Organized monolayer of thermosensitive microgel beads prepared by double-template polymerization Reviewed

Photochromic gels

TAKEOKA Yukikazu

Photochemistry Vol. 38 ( 2 ) page： 126-129 - 129 2007.9

Takamasa Sakai, Yukikazu Takeoka, Takahiro Seki, Ryo Yoshida

LANGMUIR Vol. 23 ( 17 ) page： 8651 - 8654 2007.8

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

A 2D close-packed array of thermosensitive microgel beads was prepared by the double-template polymerization method. First, a 2D colloidal crystal of silica beads with 10 mu m diameter was obtained by the solvent evaporation method. This monolayer of colloidal crystals can serve as the first template for the preparation of macroporous polystyrene. The macroporous polystyrene trapping the crystalline order can be used as a negative template for fabricating gel beads arrays. A functional surface using thermosensitive poly(N-isopropylacrylamide) gel beads array was fabricated by the double-template polymerization method.

DOI： 10.1021/la700448t

Photoresponsive slide-ring gel Reviewed

Taiga Sakai, Harumi Murayama, Shusaku Nagano, Yukikazu Takeoka, Masatoshi Kidowaki, Kohzo Ito, Takahiro Seki

ADVANCED MATERIALS Vol. 19 ( 15 ) page： 2023 - + 2007.8

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-V C H VERLAG GMBH

Slide-ring topological gels with mobile cross-linking units are a new class of soft materials that exhibit distinct features differing from those of conventional chemically or physically crosslinked gels. Photoresponsive behavior arising from the dynamic nature of the cross-linkers is demonstrated for a slide-ring, gel prepared by adding azobenzene units to the mobile a-cyclodextrin units of a poly(ethylene oxide)based polyrotaxane (see figure).

DOI： 10.1002/adma.200700457

Biform structural colored hydrogel for observation of subchain conformations Reviewed

Yukikazu Takeoka, Takahiro Seki

MACROMOLECULES Vol. 40 ( 15 ) page： 5513 - 5518 2007.7

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

We prepared a biform structural colored thermosensitive gel using both a close-packed colloidal crystal and a wing of a morpho butterfly. The porous portion of the gel obtained by the close-packed colloidal crystal as a template exhibits a change in "structural color" according to the volume when the water temperature is altered. Meanwhile, the portion where tiny scales of the wing are strewn on the surface of the gel (a morpho gel) also reveals "structural color", but irrespective of the volume change. The reflection spectrum from "the morpho gel" portion provides the standard value of the peak position, lambda(max,0), indicating that the subchains in the gel are Gaussian chains. Consequently, we can estimate the linear expansion factor alpha of the subchains by comparing the peak positions of the reflection spectra from the porous gel, lambda(max), and from the morpho gel, lambda(max,0): lambda(max)/lambda(max,0) similar to alpha. We can detect the change in the conformation of subchains in the gel in response to the external perturbations surrounding the gel with the naked eye and/or spectroscopic methods through the comparison of the both structural colors.

DOI： 10.1021/ma0701078

Organized Thermosensitive Microgel Bead Monolayer Prepared by Double Template Polymerization

SAKAI Takamasa, TAKEOKA Yukikazu, SEKI Takahiro, YOSHIDA Ryo

Vol. 64 ( 1 ) page： 45-49 2007.1

*Thermally-Adjustable Multicolor Photochromic Hydrogel Reviewed

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

Angew. Chem. Int. Ed. Vol. 46 page： 1688-1692 2007

二段階鋳型重合法を用いた温度応答型ゲル微粒子単層組織化膜の作製 Reviewed

酒井崇匡、竹岡敬和、関　隆広、吉田　亮

高分子論文集 Vol. 64 page： 45-49 2007

Organized monolayer of thermosensitive microgel beads prepared bydouble template polymerization Reviewed

Sakai, T., Takeoka, Y., Seki, T., Yoshida, R.

Langmuir Vol. 23 page： 8651-8654 2007

Photoresponsive Slide-Ring Gel Reviewed

Sakai, T. Murayama, H., Nagano, S., Takeoka, Y., Kidowaki, M., Ito, K., Seki, T.

Adv. Mater. Vol. 23 page： 8651-8654 2007

Biform Structural Colored Hydrogel For Observation of Subchain Conformations Reviewed

Takeoka, Y., Seki, T.

Macromolecules Vol. 40 page： 5513-5518 2007

*Electro- and Thermo- chromic Hydrogel as Full-color Indicator Reviewed

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

Adv. Mater. Vol. 19 page： 2807-2812 2007

Organized thermosensitive microgel bead monolayer prepared by double template polymerization Reviewed

Takamasa Sakai, Yukikazu Takeoka, Takahiro Seki, Ryo Yoshida

KOBUNSHI RONBUNSHU Vol. 64 ( 1 ) page： 45 - 49 2007

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：SOC POLYMER SCIENCE JAPAN

A 2D close-packed array of thermosensitive microgel beads was prepared by a double template polymerization method. Firstly, colloidal crystals of silica beads were obtained by solvent evaporation method. A concave and rather flat meniscus was formed at liquid-air interface by using O-rings. This monolayer of colloidal crystal can serve as the first template for preparation of macroporous polystyrene. The macroporous polymer template that trapped the crystalline order was soaked in pre-gel solution as the second template, and then polymerization was carried out in the pores. By etching the surrounding polystyrene template, we obtained a 2D monolayer of thermosensitive microgel beads. The 2D monolayer of the gel beads may be utilized as a functional surface for several applications to optical device and biomaterials.

DOI： 10.1295/koron.64.45

A thermally adjustable multicolor photochromic hydrogel

Matsubara Kazuki, Watanabe Masayoshi, Takeoka Yukikazu

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Vol. 46 ( 10 ) page： 1688-1692 2007

Organized thermosensitive microgel bead monolayer prepared by double template polymerization

Sakai Takamasa, Takeoka Yukikazu, Seki Takahiro, Yoshida Ryo

KOBUNSHI RONBUNSHU Vol. 64 ( 1 ) page： 45-49 2007

A thermally adjustable multicolor photochromic hydrogel

Matsubara Kazuki, Watanabe Masayoshi, Takeoka Yukikazu

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Vol. 46 ( 10 ) page： 1688-1692 2007

A thermally adjustable multicolor photochromic hydrogel

Matsubara Kazuki, Watanabe Masayoshi, Takeoka Yukikazu

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Vol. 46 ( 10 ) page： 1688-1692 2007

二段階鋳型重合法を用いた温度応答型ゲル微粒子単層組織化膜の作製 Reviewed

酒井崇匡, 竹岡敬和, 関隆広, 吉田亮

高分子論文集 Vol. 64 page： 45-49 2007

Visualizing conformations of subchains by creating optical wavelength-sized periodically ordered structure in hydrogel Reviewed International journal

Yukikazu Takeoka, Takahiro Seki

LANGMUIR Vol. 22 ( 24 ) page： 10223 - 10232 2006.11

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

Thick single-crystalline fcc colloidal crystals exhibiting structural color are obtained by a solvent evaporation method from silica colloidal particle suspensions. A periodically ordered interconnecting porous structure can be imprinted in thermosensitive N-isopropylacrylamide (NIPA) gels by using the colloidal crystals as templates. The porous structure endows a structural color to the NIPA gels. We find that the peak position of the reflection spectra from the porous gels (lambda(max)') is expressed as a function of the swelling degree and is synchronized with the change in the swelling degree. The color can be precisely tuned by simply changing the amount of the monomer and the cross-linker in the pre-gel solutions. We can estimate the linear expansion factor alpha (>= 1) of the subchains by comparing the peak position at a given situation (lambda(max)') and the reference state (lambda(max,0)'), in which the subchains behave as Gaussian coils. Creating the periodically ordered structure, which is similar in size to the wavelength of optical light, in the gels allows us to determine the behavior of polymer chains by observing the structural color.

DOI： 10.1021/la061945i

Visualizing Conformations of Subchains in Structural Colored Gel

TAKEOKA Yukikazu

MEMBRANE Vol. 31 ( 6 ) page： 296-301 - 301 2006.11

Language：English Publishing type：Research paper (scientific journal) Publisher：THE MEMBRANE SOCIETY OF JAPAN

We prepared porous polymer gels using a colloidal crystal as a template. The porous structure endows a structural
color to polymer gels. We found that the peak position of the reflection spectra from the porous gels (λmax) is
expressed as a function of the swelling degree, and is synchronized with the change in the swelling degree. We can
estimate the linear expansion factor α of the subchains by comparing the peak position at a given situation (λmax)
and the reference state (λmax, 0), in which the subchains behave as Gaussian coils. Creating the periodically ordered structure, which is similar in size to the wavelength of optical light, in the gels allows us to determine the behavior of polymer chains by observing the structural color.

DOI： 10.5360/membrane.31.296

Preparations and optical properties of. ordered arrays of submicron gel particles: Interconnected state and trapped state Reviewed International journal

M Kumoda, M Watanabe, Y Takeoka

LANGMUIR Vol. 22 ( 9 ) page： 4403 - 4407 2006.4

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

Two types of thermosensitive opal-structured hydrogel systems, "interconnected" and "trapped" gel particle arrays, were newly developed by extremely simple methods using silica colloidal crystal as a template. Although both systems diffract visible light following Bragg's law combined with Snell's law, the temperature dependences of their optical properties were quite different. The "interconnected" array exhibited a reversible change in the peak values of the reflection spectra, mainly determined by the swelling ratio of the hydrogel, as a function of the water temperature. Since the swelling ratio is dominant over the peak value, we can observe water temperature through the color of the interconnected type of gel membrane. The "trapped" array revealed a reversible change in the peak intensity of the reflection spectra with the change in temperature, whereas no change in the peak position was observed. We can interpret this phenomenon in the following ways. As the rise in temperature causes a decrease in the water content of the NIPA gel particles, the gel particles becomes stickier on the cavity wall of polystyrene PPM. This may induce a disturbance in the ordered array of the gel particles and form many layers of rough surfaces in the inverse opal structure of the PPM. This situation may lead to the stronger diffused reflection of light from the gel particles, resulting in the decrease in peak intensity at higher temperatures.

DOI： 10.1021/la060224g

Photomechanical effect of azobenzene liquid crystalline gel impregnated with low molecular weight liquid crystals.

Visualizing Conformations of Subchains by Creating Optical Wavelength-Sized Periodically Ordered Structure in Hydrogel Reviewed

Takeoka, Y. and Seki, T.

Langmuir Vol. 22 page： 10223-10232 2006

Preparations and optical properties of ordered arrays of submicron gel particles: Interconnected state and trapped state Reviewed

Kumoda, M., Watanabe, M., Takeoka, Y.

Langmuir Vol. 22 page： 4403-4407 2006

HAYATA Yuki, NAGANO Shusaku, TAKEOKA Yukikazu, SEKI Takahiro

Proceedings of Japanese Liquid Crystal Society Annual meeting Vol. 2006 ( 0 ) page： 175-175 - 175 2006

Language：English Publishing type：Research paper (scientific journal) Publisher：THE JAPANESE LIQUID CRYSTAL SOCIETY

Crosslinked side-chain liquid crystalline gels thin films containing azobenzene moieties were prepared by photopolymerized under visible light (436 nm) irradiation in the liquid crystalline state. The monodomain and polydomain gels were prepared on a rubbed and non-rubbed polymer film, respectively. Swelling and shrinkage in low molecular weight liquid crystal solvents were induced by the photoisomerization of azobenzene. Because the amount of azobenzene moieties were lowered to 3 wt%, the whole volume changed, and the photoisomerization behavior could be precisely evaluated by optical microscopy and UV-Vis spectroscopy.

DOI： 10.11538/ekitou.2006.0.175.0

Structural Colored Gel

TAKEOKA Yukikazu

Vol. 54 ( 4 ) page： 258-263 - 263 2005.4

Ionic conductivity and thermal stability of room temperature molten salts perfluorosulfonic acid membranes for fuel cell application Reviewed

S Mitsushima, R. Sakamoto, K. Kudo, Y. Takeoka, N. Kamiya, and Ken-ichi Ota

J. New Materials for Electrochem. Sys. Vol. 1 page： 77-84 2005

高分子科学最近の進歩構造色ゲル

竹岡敬和

高分子 Vol. 54 ( 4 ) page： 258-263 - 263 2005

Surface activity and redox behavior of a non-ionic surfactant containing a phenothiazine group Reviewed

MABH Susan, A Ishibashi, Y Takeoka, M Watanabe

COLLOIDS AND SURFACES B-BIOINTERFACES Vol. 38 ( 3-4 ) page： 167 - 173 2004.11

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

A novel non-ionic surfactant, alpha-(phenothiazinylhexyl)-omega-hydroxy-oligo(ethylene oxide) (PCPEG) containing phenothiazine as an electroactive group has been synthesized. Fundamental interfacial behavior of the surfactant at the air/water interface has been investigated by means of surface tensiometry to provide an insight into the relationship between the structure of the hydrophobic moiety and the surfactant properties. A comparison of diffusivity of PCPEG in the aqueous phase with that in the acetonitrile solution at high PCPEG concentrations shows that micellization has a pronounced effect on the redox behavior of PCPEG. The electrochemical responses for PCPEG aqueous solutions at the interface of a glassy carbon electrode are fairly dependent on the concentration of PCPEG. Above CMC, PCPEG molecules self-associate to form micellar aggregates and the formation and disruption of micelles can be reversibly controlled by change in the redox state of the phenothiazine group. The cyclic voltammetric responses for PCPEG aqueous solutions have been correlated with the dissolved states to explain the distinctive feature of the surfactant. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.colsurfb.2004.01.016

Structural Colored Gel

TAKEOKA Yukikazu, WATANABE Masayoshi

NIPPON GOMU KYOKAISHI Vol. 77 ( 5 ) page： 155-158 - 158 2004.5

Language：English Publishing type：Research paper (scientific journal) Publisher：THE SOCIRETY OF RUBBER SCIENCE AND TECHNOLOGYY, JAPAN

A periodically ordered interconnecting porous structure could be imprinted in hydrogels by using closest packing silica colloidal crystals as mesoscopically sized templates. The interconnecting porous structure provides fast response to an infinitesimal change of environment for reversible swelling and shrinking of the hydrogels, while the periodically ordered mesoscopical structure endows a structural color in the gel. The structural color with different optical behaviors can be tuned by simply changing the amount of the cross-linker in the pre-gel solutions. The structural color imprinted in the gel is quickly synchronized with the change in the volume of the gels. The newly invented porous hydrogels possess optical properties as environmentally sensitive smart gels.

DOI： 10.2324/gomu.77.155

Surface activity and redox behavior of a non-ionic surfactant containing a phenothiazine group Reviewed

Susan, M.A.B.H., Ishibashi, A., Takeoka, Y. and Watanabe, M.

Colloids and Surfaces B-Biointerfaces Vol. 38 page： 167-173 2004

Controlled multistructural color of a gel membrane Reviewed

Y Takeoka, M Watanabe

LANGMUIR Vol. 19 ( 23 ) page： 9554 - 9557 2003.11

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

A "smart" soft membrane exhibiting controlled multistructural color has been synthesized by the mechanical immobilization of a single side of a polymerized nonclosest packing colloidal crystal. A tapered gel with one fixed surface on a gel-bond film reveals monostructural color. After a partial hydrolysis of the gel to change its volume from the original size, the structural color varies depending on the thickness of the membrane. The tone can be tuned by simply changing the composition of the mixed solvent.

DOI： 10.1021/la0344175

Self-sustaining peristaltic motion on the surface of a porous gel Reviewed

Y Takeoka, M Watanabe, R Yoshida

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Vol. 125 ( 44 ) page： 13320 - 13321 2003.11

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

Many materials in living organisms exhibit self-sustaining 
oscillations of chemical and/or physical organization, 
for example,the peristaltic motion of the intestinal tract. 
Some artificial materials have similar properties and thus the 
potential for mimicking biological functions.Now researchers in 
Japan have developed a polymer-gel system that undergoes 
colour changes such that the oscillations can be observed on the 
surface of the gel for the first time (Takeoka,Y.,Watanabe,M.& 
Yoshida,R.Journal of the American Chemical Society 125, 
13320.V13321; 2003).The gel consists of two monomers, 
N-isopopylacrylamide,which controls the swelling and collapse 
of the gel in response to temperature,and a Ru-complex. 
Under certain chemical conditions,the Ru-complex ion 
catalyses a specific reaction (BZ) in which the ion is alternately 
oxidized and reduced as the reaction propagates,resulting in 
colour changes.When the gel is simultaneously subjected to 
changes in temperature,the swelling response of the gel 
occurs in parallel with the BZ reaction,resulting in waves of colour 
changes concomitant with the peristaltic motion.The colour 
tunability of these gels have the potential for use in devices

DOI： 10.1021/ja036904c

Tuning structural color changes of porous thermosensitive gels through quantitative adjustment of the cross-linker in pre-gel solutions Reviewed

Y Takeoka, M Watanabe

LANGMUIR Vol. 19 ( 22 ) page： 9104 - 9106 2003.10

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

DOI： 10.1021/la035142w

Template synthesis and optical properties of chameleonic poly(N-isopropylacrylamide) gels using closest-packed self-assembled colloidal silica crystals Reviewed

Y Takeoka, M Watanabe

ADVANCED MATERIALS Vol. 15 ( 3 ) page： 199 - + 2003.2

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-V C H VERLAG GMBH

Smart macroporous hydrogels with a range of optical behavior have been prepared using colloidal crystals as templates. The structural color imprinted in the gel (see Figure and cover) varies with a change in the volume of the gel. It is now possible to build a soft material that displays the various structural colors available to living things.

Template synthesis of poly(N-isopropylacrylamide) minigels using interconnecting macroporous polystyrene Reviewed

M Kumoda, Y Takeoka, M Watanabe

LANGMUIR Vol. 19 ( 3 ) page： 525 - 528 2003.2

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

Thermosensitive uniform-sized poly(N-isopropylacrylamide) minigels with diameters of several micrometers were synthesized by a double template method using silica particles as original molds. The first template composed of the silica particles produced a macroporous polystyrene as the second template to decide the shape and the size of the minigels. The resultant minigels in the second template covalently interconnect with each other. After the minigels were collapsed in each compartment of the macroporous polystyrene, the separated minigel particles were obtained.

DOI： 10.1021/la020758r

Polymer Gels that Memorize Structures of Mesoscopically Sized Templates Reviewed

Takeoka, Y, Watanabe, M

Langmuir Vol. 18 page： 5977-5980 2003

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

H Saito, Y Takeoka, M Watanabe

CHEMICAL COMMUNICATIONS ( 17 ) page： 2126 - 2127 2003

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

DOI： 10.1039/b304306a

Self-Sustaining Peristaltic Motion on the Surface of a Porous Gel Reviewed

Takeoka, Y., Watanabe, M., and Yoshida, R.

J. Am. Chem. Soc Vol. 125 page： 13320 2003

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

Many materials in living organisms exhibit self-sustaining
oscillations of chemical and/or physical organization,
for example,the peristaltic motion of the intestinal tract.
Some artificial materials have similar properties and thus the
potential for mimicking biological functions.Now researchers in
Japan have developed a polymer-gel system that undergoes
colour changes such that the oscillations can be observed on the
surface of the gel for the first time (Takeoka,Y.,Watanabe,M.&
Yoshida,R.Journal of the American Chemical Society 125,
13320.V13321; 2003).The gel consists of two monomers,
N-isopopylacrylamide,which controls the swelling and collapse
of the gel in response to temperature,and a Ru-complex.
Under certain chemical conditions,the Ru-complex ion
catalyses a specific reaction (BZ) in which the ion is alternately
oxidized and reduced as the reaction propagates,resulting in
colour changes.When the gel is simultaneously subjected to
changes in temperature,the swelling response of the gel
occurs in parallel with the BZ reaction,resulting in waves of colour
changes concomitant with the peristaltic motion.The colour
tunability of these gels have the potential for use in devices used
for determining oscillations in nonlinear chemical reactions.

Controlled Multi-Structural-Color of a Gel Membrane Reviewed

Takeoka, Y. and Watanabe, M.

Langmuir Vol. 19 page： 9554-9557 2003

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

Saito, H., Takeoka, Y. and Watanabe, M.

Chem. Commun. page： 2126-2127 2003

Polymer Gels that Memorize Structures of Mesoscopically Sized Templates Reviewed

Takeoka, Y. and Watanabe, M.

Langmuir Vol. 18 page： 5977-5980 2003

Template synthesis of poly(N-isopropylacrylamide) minigels using interconnecting macroporous polystyrene Reviewed

Kumoda, M., Takeoka, Y. and Watanabe, M.

Langmuir Vol. 19 page： 525-528 2003

Template synthesis and optical properties of chameleonic poly(N-isopropylacrylamide)gels using closest-packed self-assembled colloidal silica crystals Reviewed

Takeoka, Y. and Watanabe, M.

Adv. Mater, Vol. 15 page： 199-201 2003

Simple and Precision Preparation of Porous Gel for Colorimetric Chemical Sensor by Templating Technique Reviewed

Nakayama, D., Takeoka, Y., Watanabe, M., Kataoka, K.

Angew. Chem. Int. Ed. Vol. 42 page： 4197-4200 2003

Tuning Structural Color Changes of Porous Thermo-sensitive Gels Through Quantitative Adjustment of The Cross-linker in Pre-gel Solutions Reviewed

Takeoka, Y. and Watanabe, M.

Langmuir Vol. 19 page： 9104-9106 2003

Simple and precise preparation of a porous gel for a colorimetric glucose sensor by a templating technique Reviewed

D Nakayama, Y Takeoka, M Watanabe, K Kataoka

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Vol. 42 ( 35 ) page： 4197 - 4200 2003

Reversible adsorption of calcium ions by imprinted temperature sensitive gels Reviewed

C Alvarez-Lorenzo, O Guney, T Oya, Y Sakai, M Kobayashi, T Enoki, Y Takeoka, T Ishibashi, K Kuroda, K Tanaka, GQ Wang, AY Grosberg, S Masamune, T Tanaka

JOURNAL OF CHEMICAL PHYSICS Vol. 114 ( 6 ) page： 2812 - 2816 2001.2

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER INST PHYSICS

With the aim of developing polymeric gels sensitive to external stimuli and able to reversibly adsorb and release divalent ions, copolymer gels of N-isopropylacrylamide (NIPA) and methacrylic (MAA) monomers were prepared. We chose calcium as a target divalent ion. Two MAAs form a complex with a calcium ion, and the NIPA component allows the polymers to swell and shrink reversibly in response to temperature. The adsorbing site develops an affinity to target ions when the adsorbing molecules come into proximity, but when they are separated, the affinity diminishes. To enhance the affinity to calcium, an imprinting technique was applied using Ca2+ and Pb2+ ions as templates in methylsulfoxide and dioxane media, respectively. The adsorption capacity of the imprinted gels was compared with that of the nonimprinted gels, and the effects of the templates, the solvents, and the amount of methacrylic monomers used in the synthesis and the medium temperature over the Ca2+ adsorption capacity of the gels from aqueous solutions were evaluated. The analysis of the adsorption revealed that (a) the adsorption can be described by the Langmuir isotherms; (b) there is an approximately linear relationship between saturation and methacrylic monomer concentration; (c) the affinity depends on the degree of gel swelling or shrinkage that can be switched on and off by temperature; (d) in the shrunken state, the affinity depends approximately linearly on the MAA concentration in the imprinted gels, whereas in the nonimprinted gels it is proportional to the square of MAA concentration; (e) the imprinted gels adsorb more than the nonimprinted gels when MAA concentration is less than that of permanent cross linkers. The success of imprinting of CaMAA(2) and PbMAA(2) complex is evidence for memory of such complex onto the weakly cross-linked gel. (C) 2001 American Institute of Physics.

Reversible adsorption of calcium ions by imprinted temperature sensitive gels Reviewed

Carmen Alvarez-Lorenzo, Orhan Guney, Taro Oya, Yasuzo Sakai, Masatoshi Kobayashi, Takashi Enoki, Yukikazu Takeoka, Toru Ishibashi, Kenichi Kuroda, Kazunori 8Tanaka, Guoqiang Wang, Alexander Yu. Grosberg, Satoru Masamune, and Toyoichi Tanaka

J. Chem. Phys. Vol. 114 ( 6 ) page： 2812-2816 2001

Frustrations in polymer conformation in gels and their minimization through molecular imprinting Reviewed

T Enoki, K Tanaka, T Watanabe, T Oya, T Sakiyama, Y Takeoka, K Ito, GQ Wang, M Annaka, K Hara, R Du, J Chuang, K Wasserman, AY Grosberg, S Masamune, T Tanaka

PHYSICAL REVIEW LETTERS Vol. 85 ( 23 ) page： 5000 - 5003 2000.12

Language：English Publishing type：Research paper (scientific journal) Publisher：AMERICAN PHYSICAL SOC

We report an experimental realization of a gel system in which frustrations exist and can be minimized, thus meeting two crucial criteria predicted to enable memory of conformations in polymers. The gels consist of a thermosensitive major monomer component and two minor components. One minor component is positively charged and will form complexes around negatively charged target molecules placed in solution. The complexes can be imprinted into the gel by then cross-linking the second minor component, which will form cross-links additional to those in the major polymer matrix. The complexes are destroyed and reformed upon swelling and reshrinking of the gels, showing that memorization has been achieved.

Polymer gels that memorize elements of molecular conformation Reviewed

C Alvarez-Lorenzo, O Guney, T Oya, Y Sakai, M Kobayashi, T Enoki, Y Takeoka, T Ishibashi, K Kuroda, K Tanaka, GQ Wang, AY Grosberg, S Masamune, T Tanaka

MACROMOLECULES Vol. 33 ( 23 ) page： 8693 - 8697 2000.11

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

Weakly cross-linked heteropolymer gels that memorize molecular pairs have been designed and synthesized. The polymer consists of a main monomer component responsible for volume phase transition, methacrylic acid that adsorbs one divalent ion as a pair, and cross-links; The memory of pairing of methacrylic acids within the gels was encoded in the primary sequence of main monomers, methacrylic acids and cross-links within the gels, which was achieved by "imprinting", namely, by synthesizing gels while methacrylic monomers were paired prior to polymerization. The control gels, where methacrylic monomers were randomly distributed, showed frustration in forming pairs, whereas such frustration was completely diminished in the imprinted gels allowing the memory of pair formation.

Gel catalysts that switch on and off Reviewed

GQ Wang, K Kuroda, T Enoki, A Grosberg, S Masamune, T Oya, Y Takeoka, T Tanaka

PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Vol. 97 ( 18 ) page： 9861 - 9864 2000.8

Language：English Publishing type：Research paper (scientific journal) Publisher：NATL ACAD SCIENCES

We report development of a polymer gel with a catalytic activity that can be switched on and off when the solvent composition is changed. The gel consists of two species of monomers. The major component, N-isopropylacrylamide, makes the gel swell and shrink in response to a change in composition of ethanol/water mixtures. The minor component, vinylimidazole, which is capable of catalysis, is copolymerized into the gel network. The reaction rate for catalytic hydrolysis of p-nitrophenyl caprylate was small when the gel was swollen. In contrast, when the gel was shrunken, the reaction rate increased 5 times. The activity changes discontinuously as a function of solvent composition, thus the catalysis can be switched on and off by an infinitesimal change in solvent composition. The kinetics of catalysis by the gel in the shrunken state is well described by the Michaelis-Menten formula, indicating that the absorption of the substrate by the hydrophobic environment created by the N-isopropylacrylamide polymer in the shrunken gel is responsible for enhancement of catalytic activity, In the swollen state, the rate vs. active site concentration is linear, indicating that the substrate absorption is not a primary factor determining the kinetics, Catalytic activity of the gel is studied for substrates with various alkyl chain lengths; of those studied the switching effect is most pronounced for p-nitrophenyl caprylate.

Study of the correlation of the cyclic voltammetric responses of a nonionic surfactant containing an anthraquinone group with the dissolved states Reviewed

Md. Abu Bin Hasan Susan, Mahbuba Begum, Yukikazu Takeoka, Masayoshi Watanabe

Langmuir Vol. 16 ( 7 ) page： 3509 - 3516 2000.4

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

Cyclic voltammetric behavior of a nonionic surfactant, α-(anthraquinonyloxyhexyl)-ω-hydroxy-oligo-(ethylene oxide), ACPEG, has been studied in detail in aqueous media with NaCl as the supporting electrolyte. Attempts have been made to correlate the electrochemical responses with the dissolved states of the surfactant. The shapes of the cyclic voltammograms at a glassy carbon electrode have proved to be fairly dependent on the concentration of ACPEG and on the redox state of the anthraquinone group. Below the critical micelle concentration (cmc), the cyclic voltammogram (v = 10 mV/s) corresponds to the surfactant molecules adsorbed onto the electrode surface. The adsorption of ACPEG molecules at the electrode surface is very weak in nature owing to its low surface activity. A high cmc value and weak adsorption allow diffusion of the monomeric species prior to the reduction to contribute to the total current even below the cmc. At concentrations higher than the cmc, the diffusion-controlled waves are superimposed on the surface waves, and far above the cmc, the voltammetric shape is of a typical diffusion-controlled species. Above the cmc, self-association of ACPEG results in the formation of micellar aggregates, which diffuse to the electrode surface to dominate the adsorption wave. The redox process is influenced by the formation of a quinhydrone-like charge transfer complex. The cyclic voltammetrically determined apparent diffusion coefficient of the micellar solutions changes continuously with concentration
with decreasing concentration the apparent diffusion coefficient approaches the monomeric diffusion coefficient while with increasing concentration it approaches the micellar value. This has been interpreted in terms of change in the diffusion species by dissociation of the micelles formed above the cmc to monomers in the concentration gradient in the diffusion layers. The formation and dissociation reaction can be reversibly controlled by a change in the redox state. A CEC mechanism with the electrochemical reaction coupled with the preceding disruption reaction of the micelles (CE) and the following protonation reaction of the reduced state (EC) has been inferred.

DOI： 10.1021/la991033z

Effect of pH and the extent of micellization on the redox behavior of non-ionic surfactants containing an anthraquinone group Reviewed

MA Susan, M Begum, Y Takeoka, M Watanabe

JOURNAL OF ELECTROANALYTICAL CHEMISTRY Vol. 481 ( 2 ) page： 192 - 199 2000.2

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE SA

Cyclic voltammetry has been employed for the study of aqueous electrochemistry of the surfactants, alpha-(anthraquinonyloxyhexyl)-omega-hydroxy-oligo(ethylene oxide) (ACPEG) and alpha-anthraquinonyl-omega-hydroxy-oilgo (ethylene oxide) (APEG), which have wide differences in surface activity. Potential-pH diagrams have been constructed and the various features of the diagrams have been analyzed in the light of the change in solution equilibria and the difference in the extent of micellization. The redox potentials of the surfactants have been found to exhibit strong pH dependence. The electrode reaction involves two-electron reduction of anthraquinone (AQ) to its dianion (AQ(2-)), which is highly sensitive to the pH of the solution. At controlled pH, potential-pH plots allow the establishment of the values of the ionization constants for dihydroanthraquinone (AQH(2)) and its monoanion (AQH(-)) as pK(a)(1) = 7.83 and pK(a)(2) = 11.38, respectively. Under unbuffered conditions, the effective pH close to the electrode surface controls the potential of the electrode process. The changeover from the H+-available to the H+-depleted electrode process gives rise to a sudden jump in potential. In highly alkaline solutions, AQ forms an adduct with hydroxyl ion, which causes a linear decrease in the potentials with increase in pH. The different extent of micellization results in a difference in the peak current and the half wave potentials (E-1/2) for ACPEG and APEG but causes no significant change in the shapes of the E-1/2-DH diagrams. This has been explained in terms of the disruption reaction of the micelles, preceding the electrochemical reaction. (C) 2000 Elsevier Science S.A. All rights reserved.

A study to correlate the electrochemical responses of a non-ionic surfactant containing an anthraquinine group with the dissolved states Reviewed

Susan, M.A.B.H, Begum, M, Takeoka, Y, Watanabe, M

Langmuir Vol. 16 page： 3509-3516 2000

Frustrations in polymer conformation in gels and their minimization through molecular imprinting Reviewed

Takashi Enoki, Kazunori Tanaka, Tsuyoshi Watanabe, Taro Oya, Takaharu Sakiyama, Yukikazu Takeoka, Kenji Ito, Guoqiang Wang, Masahiko Annaka, Kazuhiro Hara, Rose Du, Jeffrey Chuang, Kevin Wasserman, Alexander Yu. Grosberg, Satoru Masamune, and Toyoichi Tanaka

Phys. Rev. Lett. Vol. 85 page： 5000-5003 2000

A study to correlate the electrochemical responses of a non-ionic surfactant containing an anthraquinine group with the dissolved states Reviewed

Susan, M.A.B.H., Begum, M., Takeoka, Y. and Watanabe, M.

Langmuir Vol. 16 page： 3509-3516 2000

Effect of pH and the extent of micellization on the redox behavior of non-ionic surfactants containing an anthraquinone group Reviewed

Susan, M.A.B.H., Begum, M., Takeoka, Y. and Watanabe, M.

J. Electroanal. Chem. Vol. 481 page： 192-199 2000

Polymer Gels That Memorize Elements of Molecular Conformation Reviewed

Alvarez-Lorenzo, Carmen; Guney, Orhan; Oya, Taro; Sakai, Yasuzo; Kobayashi, Masatoshi; Enoki, Takashi; Takeoka, Yukikazu; Ishibashi, Toru; Kuroda, Kenichi, Alexander Grosberg, and Toyoichi Tanaka

Macromolecules Vol. 33 page： 8693-8697 2000

Gel catalysts that switch on and off Reviewed

Guoqiang Wang, Kenichi Kuroda, Takashi Enoki, Alexander Grosberg, Satoru Masamune, Taro Oya, Yukikazu Takeoka, and Toyoichi Tanaka

Proc. Natl. Acad. Sci. USA Vol. 97 page： 9861-9864 2000

Reversible molecular adsorption based on multiple-point interaction by shrinkable gels Reviewed

T Oya, T Enoki, AY Grosberg, S Masamune, T Sakiyama, Y Takeoka, K Tanaka, GQ Wang, Y Yilmaz, MS Feld, R Dasari, T Tanaka

SCIENCE Vol. 286 ( 5444 ) page： 1543 - 1545 1999.11

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER ASSOC ADVANCEMENT SCIENCE

A general approach is presented for creating polymer-gels that can recognize and capture a target molecule by multiple-point interaction and that can reversibly change their affinity to the target by more than one order of magnitude. The polymers consist of majority monomers that make the gel reversibly swell and shrink and minority monomers that constitute multiple-point adsorption centers for the target molecule, Multiple-point interaction is experimentally proven by power Laws found between the affinity and the concentration of the adsorbing monomers within the gels.

First order phase transition and evidence for frustrations in polyampholytic gels Reviewed

Y Takeoka, AN Berker, R Du, T Enoki, A Grosberg, M Kardar, T Oya, K Tanaka, GQ Wang, XH Yu, T Tanaka

PHYSICAL REVIEW LETTERS Vol. 82 ( 24 ) page： 4863 - 4865 1999.6

Language：English Publishing type：Research paper (scientific journal) Publisher：AMERICAN PHYSICAL SOC

Polyampholyte gel, frustrated by the conflicting interactions between its positive and negative monomers, c-an undergo a sharp discontinuous phase transition driven by changing either gel composition or solvent quality and/or permeability. This finding completes the investigation of all four major interactions involved in the biomolecular machinery with respect to their role in the behavior of polymer gels, considered here as a model of biopolymer system. The result also sheds light on the possible role of frustrations in biomolecular systems, such as proteins. [S0031-9007(99)09334-5].

First Order Phase Transition and Evidence for Frustrations in Polyampholyte Gels Reviewed

Yukikazu Takeoka, A. Nihat Berker, Rose Du, Takashi Enoki, Alexander Grosberg, Mehran Kardar, Taro Oya, Kazunori Tanaka, Guoqiang Wang, Xiaohong Yu, Toyoichi Tanaka

Phys. Rev. Lett. Vol. 82 page： 4863-4865 1999

Reversible Molecular Adsorption Based on Multiple-Point Interaction by Shrinkable Gels Reviewed

Taro Oya, Takashi Enoki, Alexander Yu. Grosberg, Satoru Masamune, Takaharu Sakiyama, Yukikazu Takeoka, Kazunori Tanaka, Guoqiang Wang, Yasar Yilmaz, Michael S. Feld, Ramachandra Dasari, and Toyoichi Tanaka

Science Vol. 286 page： 1543-1545 1999

Reversible molecular adsorption as a tool to observe freezing and to perform design of heteropolymer gels Reviewed

T Tanaka, T Enoki, AY Grosberg, S Masamune, T Oya, Y Takaoka, K Tanaka, CN Wang, GQ Wang

BERICHTE DER BUNSEN-GESELLSCHAFT-PHYSICAL CHEMISTRY CHEMICAL PHYSICS Vol. 102 ( 11 ) page： 1529 - 1533 1998.11

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-V C H VERLAG GMBH

Protein folding is one of the most challenging problems in science. How can polymers memorize and fold into unique conformations? How can they recognize molecules, catalyze chemical reactions, transfer molecular information, and create motions? The principle behind these mechanisms lies in the concept of thermodynamically stable phases of heteropolymers. Recent theories predict that the collapsed phase should be further classified into three phases: freely fluctuating like liquid, frozen in degenerate conformations, and frozen in a unique conformation. This yields a clue on how one can attempt creation artificial polymers capable to mimic some of the protein properties and functions. The reversible adsorption of target molecules is suggested as a primary means to achieve this goal. Target molecules with multiple adsorption sites play a twofold role. First, they mediate specific interactions between monomers and thus serve as "gluons". Second, monitoring the adsorption provides the experimental possibility to test directly on monomer contacts, which is directly related to observation of the order parameter associated with heteropolymer freezing transition. A slight change in the backbone conformation alters the spacial arrangement of the group, allowing for reversible adsorption and release. Polymer gels are developed that can reversibly change their affinity to target molecules by orders of magnitude. The gels are made of copolymers of backbone monomers that can reorganize themselves through thermal volume phase transition and of monomers that can attract the target at multiple contact points. Further the gels "imprinted" with the target showed a marked increase in the affinity, thus mimicing a protein-like ability to memorize and recognize certain target.

Reversible molecular adsorption as a tool to observe freezing and to perform design of heteropolymer gels Reviewed

Tanaka, Toyoichi; Enoki, Takashi; Grosberg, Alexander Y.; Masamune, Satoru; Oya, Taro; Takaoka, Yukikazu; Tanaka, Kazunori; Wang, Changnan; Wang, Guoqiang.

Ber. Bunsen-Ges. Vol. 102 ( 11 ) page： 1529-1533 1998

Effect of supporting electrolyte concentration on the electrochemical reaction of redox-active surfactant micelles in aqueous solutions Reviewed

Yukikazu Takeoka, Takashi Aoki, Kohei Sanui, Naoya Ogata, Masayoshi Watanabe

Journal of Electroanalytical Chemistry Vol. 438 ( 1-2 ) page： 153 - 158 1997.11

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

The effect of NaCl concentration on the redox potential of α-ferrocenylundecyl-ω-hydroxy-polyoxyethylene (FPEG) micelles has been studied in aqueous solutions. With increasing NaCl concentration, the anodic half-wave potentials E1/2 of cyclic voltammograms of the aqueous solutions shift to higher potential, and the peak currents of the cyclic voltammograms decrease. The results are discussed in terms of thermodynamics of the micelle formation. An equation which interprets the correlation between the E1/2, the salt concentration, diffusion coefficient of the micelle DM, and the aggregation number m, has been derived. The changes in DM and m with NaCl concentration do not explain the change in the value of E1/2. The decrease in the equilibrium constant for the micelle-disruption Kd with increasing NaCl concentration affects the redox-potential of the FPEG micellar solutions. © 1997 Elsevier Science S.A.

DOI： 10.1016/S0022-0728(97)00128-9

Effect of supporting electrolyte concentration on the electrochemical reaction of redox-active surfactant micelles in aqueous solutions Reviewed

Y Takeoka, T Aoki, K Sanui, N Ogata, R Watanabe

JOURNAL OF ELECTROANALYTICAL CHEMISTRY Vol. 438 ( 1-2 ) page： 153 - 158 1997.11

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE SA

The effect of NaCl concentration on the redox potential of alpha-ferrocenylundecyl-omega-hydroxy-polyoxyethylene (FPEG) micelles has been studied in aqueous solutions. With increasing NaCl concentration, the anodic half-wave potentials E-1/2 of cyclic voltammograms of the aqueous solutions shift to higher potential, and the peak currents of the cyclic voltammograms decrease. The results are discussed in terms of thermodynamics of the micelle formation. An equation which interprets the correlation between the E-1/2, the salt concentration, diffusion coefficient of the micelle D-M, and the aggregation number m, has been derived. The changes in D-M and m with NaCl concentration do not explain the change in the value of E-1/2. The decrease in the equilibrium constant for the micelle-disruption K-d with increasing NaCl concentration affects the redox-potential of the FPEG micellar solutions. (C) 1997 Elsevier Science S.A.

Cyclic voltammetric study of redox-active surfactant by hydrogel-modified electrode Reviewed

Y Takeoka, T Aoki, K Sanui, N Ogata, M Watanabe

POLYMER GELS AND NETWORKS Vol. 5 ( 4 ) page： 369 - 383 1997

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

The dissolved states of redox-active non-ionic surfactant (FPEG) in the swollen state of N-isopropyl acrylamide (NIPA) hydrogel have been studied by using a gel-modified electrode. The pronounced decrease in the peak current and the negative shift in the formal potential of CV at the gel-modified electrode, as compared with the normal GC electrode, was observed in the micelle-solution; this indicates that the diffusive FPEG molecules which form the micelle hardly penetrate into the NIPA gel. This result suggests that there exists all interaction between FPEG molecules and the NIFA gel in the vicinity of the surface of the NIPA gel in the micelle-solution. However, this also indicates that a small amount of FPEG molecules which can form micelles exist in the NIPA gel. (C) 1997 Elsevier Science Ltd.

Cyclic voltammetric study of redox-active surfactant by gel-modified electrode Reviewed

Yukikazu Takeoka, Takashi Aoki, Kohei Sanui, Naoya Ogata, Masayoshi Watanabe

Polymer Gels and Networks Vol. 5 page： 369-383 1997

Effect of supporting electrolyte concentration on the electrochemical reaction of redox-active surfactant micelles in aqueous solutions Reviewed

Yukikazu Takeoka, Takashi Aoki, Kohei Sanui, Naoya Ogata, Masayoshi Watanabe

J.Electroanal.Chem. Vol. 438 page： 153-158 1997

Electrochemical studies of a redox-active surfactant. Correlation between electrochemical responses and dissolved states Reviewed

Y Takeoka, T Aoki, K Sanui, N Ogata, M Watanabe

LANGMUIR Vol. 12 ( 2 ) page： 487 - 493 1996.1

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

Electrochemical studies of a nonionic surfactant, alpha-(ferrocenylundecyl)-omega-hydroxy-oligo(ethylene oxide) (FPEG), have been conducted in 0.16 M NaCl aqueous solution at a glassy carbon electrode. The correlation between electrochemical responses and dissolved states has been examined in detail. Cyclic voltammograms (upsilon = 10 mV/s) of the FPEG solutions change with the concentration; below the critical micelle concentration (cmc), the voltammetric shape is of a typical surface-confined species, while above the cmc the diffusion-controlled waves are superimposed at the cathodic side of the surface waves, and far above the cmc the voltammetric shape is of a typical diffusion-controlled species. FPEG in the aqueous solutions adsorbs onto the glassy carbon electrode surface to form a monolayer because of its surface activity. The adsorption isotherm has been represented by the Frumkin isotherm, which includes the repulsive interaction between the adsorbed FPEG molecules. Above the cmc, FPEG forms micelles. Chronoamperometrically determined apparent diffusion coefficients of the micellar solutions decrease with increasing concentrations. This has been interpreted in terms of the change in the diffusion species by disruption of the micelles into monomers at the cmc in the concentration gradient in diffusion layers. Cyclic voltammetric peak potentials of the micellar solutions shift toward the anodic side with the concentration. This behavior has been explained as the electrochemical reaction coupled with a preceding disassembled reaction of the micelles.

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

Electrochemical Studies of a Redox-active Surfactants. Correlation between Electrochemical Responses and Dissolved States Reviewed

Yukikazu Takeoka, Takashi Aoki, Kohei Sanui, Naoya Ogata, Masayoshi Watanabe

Langmuir Vol. 12 page： 487-493 1996

HJ CUI, RZ JIN, Y TAKEOKA

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

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：CROP SCIENCE SOC JAPAN

Investigations were carried out on the characters of rachilets, grains and grain weight per panicle of the growing rice plant cv. Shimokita under different planting density and nitrogen fertilizer norm conditions during the maturity stage of growth. The large vascular bundle (LVB), and small vascular bundle (SVB) of the panicle neck internode (PNI) and partial different internode were examined under a microscope. Analysing the above dare with various statistical methods, the change in LVB number of PNI and its relationship with rachilets, grains or grain weight were determined. The average numbers of LVB and SVB were 9.0 and 16.5, and the variable range were 5-13 and 11-22, respectively. The frequency distribution of these attributes in the Ist internode and itscoefficient variation was significantly larger that the other internodes. The number of LVB and SVB in PNI appeared to positively correlated; the former with the primary rachilets having a correlation coefficient (CC) of 0.894** and the latter with the secondary rachilets a CC of 0.764**. The LVB and SVB of the PNI exhibited a significantly higher positive correlation with the total grains at a CC of 0.955** and 0.850**, respectively. The number of LVB and SVB of the PNI increased with increasing nitrogen fertilizer norm. The number of LVB and SVB of the PNI decreased with increasing planting densities.

DOI： 10.1626/jcs.64.216

ELECTROCHEMICAL CONTROL OF DRUG-RELEASE FROM REDOX-ACTIVE MICELLES Reviewed

Y TAKEOKA, T AOKI, K SANUI, N OGATA, M YOKOYAMA, T OKANO, Y SAKURAI, M WATANABE

JOURNAL OF CONTROLLED RELEASE Vol. 33 ( 1 ) page： 79 - 87 1995.1

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

Electrochemical control of drug release was demonstrated by redox-active micelles of non-ionic surfactants having a ferrocenyl moiety (FPEG). The surfactants formed micelles at the concentrations above the critical micelle concentration (CMC = 0.1 mM) in normal saline solutions when they existed as the reduced form (FPEG), whereas the micelles were disassembled into monomers when they existed as the oxidized form (FPEG(+)). This change was reversible and electrochemically controlled. The electroactivity of FPEG determined by cyclic voltammetry was quite sensitive to the aggregation states. Perylene, which was used as a model of hydrophobic drugs, could be solubilized in a 2 mM FPEG normal saline solution, however, it was hardly solubilized in a 2 mM FPEG(+) solution that was made by oxidation of the former solution. Quick and discrete response for releasing perylene from the redox active micelles was achieved by using controlled potential bulk electrolysis method.

INTERACTION BETWEEN REDOX-ACTIVE NON IONIC SURFACTANT MICELLE AND POLY(ACRYLIC ACID) Reviewed

Y TAKEOKA, T AOKI, K SANUI, N OGATA, M WATANABE

KOBUNSHI RONBUNSHU Vol. 52 ( 10 ) page： 657 - 661 1995

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：SOC POLYMER SCIENCE JAPAN

A non-ionic redox active surfactant, alpha-ferrocenylundecyl-omega-hydroxy-oligo(ethylene oxide), exhibits high ability to form polymer complexes with poly(acrylic acid) at a micelle forming concentration, in spite of the low molecular weight of the oligo(ethylene oxide) site. The fraction of carboxyls associated with ether oxygens (theta) between them has a high value (ca. 0.8) which is independent of the concentration of poly(acrylic acid). The complex formation seemed to be caused by hydrogen bonding and hydrophobic interactions. The complex formation influenced on electrochemical reactions of the redox active surfactant.