Faculty Profiles - TAKEOKA, Yukikazu

Papers - TAKEOKA, Yukikazu

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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

Web of Science

Scopus

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

Web of Science

Scopus

PubMed

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.

Scopus

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

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

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

Web of Science

Scopus

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

Web of Science

Scopus

PubMed

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

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

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

Web of Science

Scopus

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

Web of Science

Scopus

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

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Papers - TAKEOKA, Yukikazu