Faculty Profiles - TAKEOKA, Yukikazu

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

CiNii Research

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