Takuya Yamamoto

Faculty of Engineering Applied Chemistry Chemistry of Functional MoleculesAssociate Professor
Institute for the Advancement of Higher EducationAssociate Professor
Last Updated :2025/02/13

■Researcher basic information

Degree

  • Ph.D., University of Utah

Researchmap personal page

Researcher number

  • 30525986

Research Keyword

  • 高分子化学
  • 超分子化学
  • Supramolecular Chemistry

Research Field

  • Nanotechnology/Materials, Polymer chemistry

Educational Organization

■Career

Career

  • 2015 - Present
    Hokkaido University, Division of Applied Chemistry, Faculty of Engineering, Associate Professor
  • 2008 - 2015
    Tokyo Institute of Technology, Graduate School of Science and Engineering, Department of Organic and Polymeric Materials, Assistant Professor
  • 2005 - 2008
    :科学技術振興機構 ERATO-SORST 相田ナノ空間プロジェクト 研究員
  • 2005 - 2008
    :Japan Science and Technology Agency ERATO-SORST Aida Nanospace Project Researcher
  • 2008
    -:Tokyo Institute of Technology Department of Organic and Polymeric Materials Assistant Professor
  • 2005 - 2005
    :科学技術振興機構 ERATO 相田ナノ空間プロジェクト 研究員
  • 2005 - 2005
    :Japan Science and Technology Agency ERATO Aida Nanospace Project Researcher
  • 2004 - 2005
    :University of Utah Department of Chemistry Postdoctoral Fellow
  • 2004 - 2005
    :University of Utah Department of Chemistry Postdoctoral Fellow

Educational Background

  • 2004, University of Utah, Department of Chemistry, United States
  • 2004, University of Utah, Department of Chemistry, United States
  • 1999, University of Utah, College of Science, Department of Chemistry, United States
  • 1999, University of Utah, College of Science, Department of Chemistry, United States

■Research activity information

Awards

  • Sep. 2017, 日本化学会コロイドおよび界面化学部会, 科学奨励賞               
    環状高分子を利用した新奇機能性ソフトマテリアルの開発
    Yamamoto Takuya
  • Feb. 2014, 東京工業大学, 手島精一記念研究賞(藤野志郎賞)               
    環状高分子の自己組織化による機能発現:トポロジー効果を利用した高機能材料の開発
    Yamamoto Takuya
  • Jul. 2013, 高分子学会関西支部, ヤングサイエンティスト講演賞               
    環状トポロジーに由来する高分子機能材料の驚異的な特性
    Yamamoto Takuya
  • Apr. 2013, 文部科学省, 科学技術分野の文部科学大臣表彰 若手科学者賞               
    環状高分子の自己組織化を利用した新奇機能材料の研究
    Yamamoto Takuya
  • Mar. 2013, 日本化学会, 若い世代の特別講演会               
    環状高分子の自己組織化による機能発現
    Yamamoto Takuya
  • Aug. 2011, 東京工業大学, 東工大挑戦的研究賞 学長特別賞               
    高分子の『かたち』に基づく機能材料開発: DDSに向けた高分子ミセルの創製
    Yamamoto Takuya
  • May 2011, 高分子学会, 高分子研究奨励賞               
    両親媒性ブロック共重合体の環状化を利用したミセルの熱安定性向上
    Yamamoto Takuya
  • Oct. 2010, 東京工業大学 大学院理工学研究科 工学系, 工学系共通経費による顕彰と研究助成 工系若手奨励賞               
    環状ポリ乳酸を用いた新規機能性材料の開発
    Yamamoto Takuya
  • May 2007, 日本化学会, 優秀講演賞               
    ノルボルネンを末端に持つ両親媒性へキサベンゾコロネン誘導体の自己組織化によるナノコイルとナノチューブの形成
    Yamamoto Takuya
  • Apr. 1999, University of Utah, Award for Outstanding Performance on the Senior Comprehensive Exam               
    Yamamoto Takuya

Papers

  • Self-assembly of malto-oligosaccharide-block-solanesol in aqueous solutions: Investigating morphology and sugar-based physiological compatibility               
    Weeranuch Lang, Ph.D., Tomohisa Watanabe, Chaehun Lee, Sho Fukushima, Feng Li, Ph.D., Takuya Yamamoto, Ph.D., Kenji Tajima, Ph.D., Takayoshi Tagami, Ph.D., Redouane Borsali, Ph.D., Kenji Takahashi, Ph.D., Toshifumi Satoh, Ph, D Dr. Takuya Isono
    Carbohydrate Polymers, Jan. 2025, [Peer-reviewed]
  • Molecular Design of a Discrete Oligosaccharide-block-Oligodimethylsiloxane System: Toward Microphase Separation with 1 nm Domain Size and Angstrom-Scale Size Control
    Taiki Nishimura, Chaehun Lee, Ryosuke Nunokawa, Yu-Hung Cheng, Feng Li, Takuya Yamamoto, Kenji Tajima, Redouane Borsali, Hsin-Lung Chen, Toshifumi Satoh, Takuya Isono
    Macromolecules, American Chemical Society (ACS), 18 Dec. 2024
    Scientific journal
  • Fully biosourced amphiphilic block copolymer from tamarind seed xyloglucan and solanesol: Synthesis, aqueous self-assembly, and drug encapsulation               
    Weeranuch Lang, Ph.D., Tomohisa Watanabe, Chaehun Lee, Takayoshi Tagami, Ph.D., Feng Li, Ph.D., Takuya Yamamoto, Ph.D., Kenji Tajima, Ph.D., Redouane Borsali, Ph.D., Kenji Takahashi, Ph.D., Toshifumi Satoh, Ph.D. Takuya Isono
    Carbohydrate Polymers, Dec. 2024, [Peer-reviewed]
  • Synthesis of Polycarbonates and Polyesters via Tetraalkylammonium Salt-catalyzed Ring-opening Polymerization               
    Suzuki, Ryota, Takagi, Satoru, Matsuda, Minori, Takuya, Yamamoto, Tajima, Kenji, Li, Feng, Isono, Takuya, Satoh, Toshifumi
    Chemistry Letters, Dec. 2024, [Peer-reviewed]
  • Molecular structure of enzyme-synthesized amylase-like chimeric isomaltomegalosaccharides and their encapsulation of the sulfasalazine prodrug               
    Weeranuch Lang, Yoshiaki Yuguchi, Chun-Yao Ke, Ting-Wei Chang, Yuya Kumagai, Wilaiwan Kaenying, Takayoshi Tagami, Feng Li, Takuya Yamamoto, Kenji Tajima, Kenji Takahashi, Takuya Isono, Toshifumi Satoh, Atsuo Kimura
    Carbohydr. Polym., 8, Nov. 2024, [Peer-reviewed]
  • Poly(butylene succinate) reinforced by small amount of grafted nanofibrillated bacterial cellulose: Toughness variability based on nanocomposites preparation method
    Hamidah binti Hashim, Xiaochao Xia, Hiroshi Kani, Shuichiro Seno, Feng Li, Takuya Isono, Takuya Yamamoto, Hirofumi Tani, Toshifumi Satoh, Kenji Tajima
    Composites Part A: Applied Science and Manufacturing, 185, 108341, 108341, Elsevier BV, Oct. 2024
    Scientific journal
  • Polyester Adhesives via One-Pot, One-Step Copolymerization of Cyclic Anhydride, Epoxide, and Lactide
    Ryota Suzuki, Toshiki Miwa, Ryosuke Nunokawa, Ayaka Sumi, Masaru Ando, Katsuaki Takahashi, Akira Takagi, Takuya Yamamoto, Kenji Tajima, Feng Li, Takuya Isono, Toshifumi Satoh
    Polymers, Sep. 2024
    Scientific journal
  • Detailed structural analyses and viscoelastic properties of nano-fibrillated bacterial celluloses
    Haruto Tsujisaki, Masaaki Hosokawa, Yuichi Takasaki, Yoshifumi Yamagata, Yui Kawabata, Daisuke Tatsumi, Shuichiro Seno, Keisuke Miyamoto, Takuya Isono, Takuya Yamamoto, Hirofumi Tani, Toshifumi Satoh, Hiroshi Orihara, Kenji Tajima
    Carbohydrate Polymer Technologies and Applications, 100565, 100565, Elsevier BV, Sep. 2024
    Scientific journal
  • Toward Fully Controllable Monomers Sequence: Binary Organocatalyzed Polymerization from Epoxide/Aziridine/Cyclic Anhydride Monomer Mixture               
    Gao, Tianle, Xia, Xiaochao, Watanabe, Tomohisa, Ke, Chun-Yao, Suzuki, Ryota, Yamamoto, Takuya, Li, Feng, Isono, Takuya, Satoh, Toshifumi
    J. Am. Chem. Soc., Jul. 2024
  • Organobase-Catalyzed Ring-opening Copolymerization of Cyclic anhydrides and Oxetanes: Establishment and Application in Block Copolymer Synthesis               
    Ota, Iyoka, Suzuki, Ryota, Mizukami, Yuta, Xia, Xiaochao, Tajima, Kenji, Yamamoto, Takuya, Li, Feng, Isono, Takuya, Satoh, Toshifumi
    Macromolecules, Apr. 2024
  • Structural study of two polymer chains of poly(2-methoxyethyl glycidyl ether)-b-poly(2-ethoxyethyl glycidyl ether) thermoresponsive block copolymers using molecular dynamics simulations
    Erika Terada, Takuya Isono, Toshifumi Satoh, Takuya Yamamoto, Toyoji Kakuchi, Shin-ichiro Sato
    Chemical Physics Letters, 840, 141137, 141137, Elsevier BV, Apr. 2024
    Scientific journal
  • Chemically Recyclable Unnatural (1→6)-Polysaccharides from Cellulose-Derived Levoglucosenone and Dihydrolevoglucosenone               
    Mizukami, Yuta, Kakehi, Yuto, Li, Feng, Yamamoto, Takuya, Tajima, Kenji, Isono, Takuya, Satoh, Toshifumi
    Feb. 2024
  • Synthesis of Amino-Functionalized Polyester via Ring-Opening Alternating Copolymerization of Glycidylamines with Cyclic Anhydrides
    Ryota Suzuki, Tianle Gao, Ayaka Sumi, Takuya Yamamoto, Kenji Tajima, Feng Li, Takuya Isono, Toshifumi Satoh
    Polymer Chemistry, Royal Society of Chemistry (RSC), 2024
    Scientific journal, Amino-functionalized polyesters (APEs) are a remarkable class of polymeric materials with a wide range of applications, e.g. as antibacterial materials, gene delivery carriers, and biodegradable plastics. However, the current APE...
  • Acetyl Cellooligosaccharide-Based Block Copolymers for Toughening Cellulose Triacetate/Poly(ε-caprolactone) Biodegradable Blends               
    Katsuhara, Satoshi, Tsuji, Yuki, Sunagawa, Naoki, Igarashi, Kiyohiko, Takahashi, Kenji, Yamamoto, Takuya, Li, Feng, Tajima, Kenji, Isono, Takuya, Satoh, Toshifumi
    ACS Sustainable Chemistry & Engineering, Jan. 2024, [Peer-reviewed]
    English
  • Ultrasmall 3D Network Morphologies from Biobased Sugar–Terpenoid Hybrid Block Co-oligomers in the Bulk and Thin Film States               
    Lee, C, ryoya komaki, Satoshi Katsuhara, Takuya Yamamoto, Kenji Tajima, Satoh Toshifumi Satoh, Takuya Isono
    Giant, Dec. 2023
  • One-Step Synthesis of Poly(amide ester)-Based Block Copolymers with Defined Phase Separation Behavior
    Tianle Gao, Feng Li, Ryota Suzuki, Huan Li, Takuya Yamamoto, Xiaochao Xia, Takuya Isono, Toshifumi Satoh
    Macromolecules, American Chemical Society (ACS), 12 Oct. 2023
    Scientific journal
  • Molecular Dynamics Calculations for the Temperature Response of Poly(alkylated tri(ethylene oxide)isocyanate) Aqueous Solution
    Shunsuke Mizutani, Shunya Kita, Naoya Sakai, Takuya Yamamoto, Andrej Koleżyński, Toyoji Kakuchi, Shin-ichiro Sato
    Macromol, 3, 3, 653, 664, MDPI AG, 08 Sep. 2023
    Scientific journal, Aqueous solutions of conventional temperature-responsive amphiphilic polymers undergo a coil–globule conformational transition around the lower critical solution temperature (LCST) that causes the polymer surfaces to become hydrophobic and the polymers to aggregate together. Isocyanate polymers with alkylated oligo(ethylene oxide) side chains are expected to have rigid main chains and, thus, do not undergo the coil–globule structural transition, but they have recently been reported to exhibit temperature-responsive properties. In this study, molecular dynamics was used to calculate the agglomeration tendencies of two chains of poly(alkylated tri(ethylene oxide)isocyanate) (PRTEOIC, where R = methyl (Me) or ethyl (Et)) in aqueous solution to elucidate the LCST phenomenon in the absence of coil–globule conformational transition. Our MD simulations showed that aggregation also occurs in rod polymers. Furthermore, we found that both (PMeTEOIC)2 and (PEtTEOIC)2 showed parallel agglomeration of the two molecular chains with increasing temperature, but only (PMeTEOIC)2 showed a metastable T-shaped agglomeration in the middle temperature range. The crossing-point temperature (TCRP) at which the density of the first hydrophobic hydration shell around the sidechain alkyl group equals the bulk water density is a useful indicator for predicting the LCST of rod polymers with dense side chains terminated by alkyl groups.
  • Rotaxane Formation of Multicyclic Polydimethylsiloxane in a Silicone Network: A Step toward Constructing “Macro-Rotaxanes” from High-Molecular-Weight Axle and Wheel Components
    Minami Ebe, Asuka Soga, Kaiyu Fujiwara, Brian J. Ree, Hironori Marubayashi, Katsumi Hagita, Atsushi Imasaki, Miru Baba, Takuya Yamamoto, Kenji Tajima, Tetsuo Deguchi, Hiroshi Jinnai, Takuya Isono, Toshifumi Satoh
    Angewandte Chemie International Edition, 135, 35, e202304493, Wiley, Jul. 2023, [Peer-reviewed]
    English, Scientific journal, Abstract

    Rotaxanes consisting of a high‐molecular‐weight axle and wheel components (macro‐rotaxanes) have high structural freedom, and are attractive for soft‐material applications. However, their synthesis remains underexplored. Here, we investigated macro‐rotaxane formation by the topological trapping of multicyclic polydimethylsiloxanes (mc‐PDMSs) in silicone networks. mc‐PDMS with different numbers of cyclic units and ring sizes was synthesized by cyclopolymerization of a α,ω‐norbornenyl‐functionalized PDMS. Silicone networks were prepared in the presence of 10–60 wt % mc‐PDMS, and the trapping efficiency of mc‐PDMS was determined. In contrast to monocyclic PDMS, mc‐PDMSs with more cyclic units and larger ring sizes can be quantitatively trapped in the network as macro‐rotaxanes. The damping performance of a 60 wt % mc‐PDMS‐blended silicone network was evaluated, revealing a higher tan δ value than the bare PDMS network. Thus, macro‐rotaxanes are promising as non‐leaching additives for network polymers.
  • Cyclopolymerization: A versatile approach to multicyclic polystyrene and polystyrene-containing multicyclic copolymer
    Ebii, Y, Mato, Y, Li, F, Tajima, K, Yamamoto, T, Isono, T, Satoh, T
    Polym. Chem., 14, 26, 3099, 3109, Royal Society of Chemistry (RSC), Jun. 2023, [Peer-reviewed]
    Scientific journal, Macromolecules with cyclic topologies have attracted significant attention because of their unique structures. Herein, we report the systematic synthesis of multicyclic polystyrene (mc-PS) via cyclopolymerization of α,ω-dinorbornenyl end-functionalized PS macromonomers...
  • All-Atom Molecular Dynamics Simulations of the Temperature Response of Poly(glycidyl ether)s with Oligooxyethylene Side Chains Terminated with Alkyl Groups
    Erika Terada, Takuya Isono, Toshifumi Satoh, Takuya Yamamoto, Toyoji Kakuchi, Shinichiro Sato
    Nanomaterials, 12 May 2023
    Scientific journal
  • Effect of degree of substitution on the microphase separation and mechanical properties of cellooligosaccharide acetate-based elastomers
    Satoshi Katsuhara, Naoki Sunagawa, Kiyohiko Igarashi, Yutaka Takeuchi, Kenji Takahashi, Takuya Yamamoto, Feng Li, Kenji Tajima, Takuya Isono, Toshifumi Satoh
    Carbohydrate Polymers, May 2023
    Scientific journal
  • Molecular Weight-Dependent Oxidation and Optoelectronic Properties of Defect-Free Macrocyclic Poly(3-hexylthiophene)
    Ryohei Sato, Atsuo Utagawa, Koji Fushimi, Feng Li, Takuya Isono, Kenji Tajima, Toshifumi Satoh, Shin-ichiro Sato, Hiroshi Hirata, Yoshihiro Kikkawa, Takuya Yamamoto
    Polymers, 15, 3, 666, 666, MDPI AG, 28 Jan. 2023
    Scientific journal, The redox behaviors of macrocyclic molecules with an entirely π-conjugated system are of interest due to their unique optical, electronic, and magnetic properties. In this study, defect-free cyclic P3HT with a degree of polymerization (DPn) from 14 to 43 was synthesized based on our previously established method, and its unique redox behaviors arising from the cyclic topology were investigated. Cyclic voltammetry (CV) showed that the HOMO level of cyclic P3HT decreases from –4.86 eV (14 mer) to –4.89 eV (43 mer), in contrast to the linear counterparts increasing from –4.94 eV (14 mer) to –4.91 eV (43 mer). During the CV measurement, linear P3HT suffered from electro-oxidation at the chain ends, while cyclic P3HT was stable. ESR and UV–Vis–NIR spectroscopy suggested that cyclic P3HT has stronger dicationic properties due to the interactions between the polarons. On the other hand, linear P3HT showed characteristics of polaron pairs with multiple isolated polarons. Moreover, the dicationic properties of cyclic P3HT were more pronounced for the smaller macrocycles.
  • Corrigendum to “Effect of hydrogen–deuterium exchange in amide linkages on properties of electrospun polyamide nanofibers” [Polymer 229 (2022) 123994](S0032386121006170)(10.1016/j.polymer.2021.123994)
    Dongyang Li, Wataru Takarada, Minoru Ashizawa, Takuya Yamamoto, Hidetoshi Matsumoto
    Polymer, 2023
    Scientific journal, The authors regret the wrong description of diffraction peaks for the polyamide 66 nanofibers (PA66 NFs). Decimal points were missing in some data. “The WAXD patterns of the PA66 NFs are characterized by two broad diffraction peaks at 2θ values of 20.7° and 23.5° for PA66-H, and at 20.7° and 23.3° for PA66-D, …” The authors also regret the inaccurate interpretation of the crystalline form and the corresponding indexes for the polyamide 11 nanofibers (PA11 NFs). Their crystalline forms were δ’ from instead of α-form. The authors have corrected Fig. 4 (e) (f), Table 2, Ref. 32, and the corresponding discussion.[Formula presented] [Table presented] “Similarly, the WAXD patterns of the δ’ crystal form of PA11 exhibit two characteristic broad reflection peaks positioned at 2θ values of 6.7° and 21.2° for PA11-H and at 6.7° and 21.2° for PA11-D, corresponding to the (001) and (010)/(110) planes, respectively (Fig. 4e and f) [32]” [32] Z. Yang, W. Takarada, H. Matsumoto, Effect of the fiber diameter of polyamide 11 nanofibers on their internal molecular orientation and properties. Macromol. Rapid Commun. 2023, 2300212. https://doi.org/10.1002/marc.202300212 The authors would like to apologize for any inconvenience caused.
  • Installation of the adamantyl group in polystyrene-block-poly(methyl mathacrylate) via Friedel–Crafts alkylation to modulate the microphase-separated morphology and dimensions
    Takuya Isono, Ema Baba, Shunma Tanaka, Ken Miyagi, Takahiro Dazai, Feng Li, Takuya Yamamoto, Kenji Tajima, Toshifumi Satoh
    Polymer Chemistry, 14, 22, 2675, 2684, Royal Society of Chemistry (RSC), 2023
    Scientific journal, We present the polystyrene block post-polymerization modification of PS-b-PMMA through Friedel–Crafts alkylation with adamantanols to modulate its microphase-separated morphology and dimensions.
  • Size Control and Enhanced Stability of Silver Nanoparticles by Cyclic Poly(ethylene glycol)
    Yubo Wang, Jose Enrico Quijano Quinsaat, Feng Li, Takuya Isono, Kenji Tajima, Toshifumi Satoh, Shin-ichiro Sato, Takuya Yamamoto
    Polymers, 14, 21, 4535, 4535, MDPI AG, 26 Oct. 2022, [Peer-reviewed], [International Magazine]
    Scientific journal, Silver nanoparticles (AgNPs) are used in a wide range of applications, and the size control and stability of the nanoparticles are crucial aspects in their applications. In the present study, cyclized poly(ethylene glycol) (c-PEG) with various molecular weights, along with linear PEG with hydroxy chain ends (HO–PEG–OH) and methoxy chain ends (MeO–PEG–OMe) were applied for the Tollens’ synthesis of AgNPs. The particle size was significantly affected by the topology and end groups of PEG. For example, the size determined by TEM was 40 ± 7 nm for HO–PEG5k–OH, 21 ± 4 nm for c-PEG5k, and 48 ± 9 nm for MeO–PEG5k–OMe when the molar ratio of PEG to AgNO3 (ω) was 44. The stability of AgNPs was also drastically improved by cyclization; the relative UV–Vis absorption intensity (A/A0 × 100%) at λmax to determine the proportion of persisting AgNPs in an aqueous NaCl solution (37.5 mM) was 58% for HO–PEG5k–OH, 80% for c-PEG5k, and 40% for MeO–PEG5k–OMe, despite the fact that AgNPs with c-PEG5k were much smaller than those with HO–PEG5k–OH and MeO–PEG5k–OMe.
  • Polyether/Polythioether Synthesis via Ring-Opening Polymerization of Epoxides and Episulfides Catalyzed by Alkali Metal Carboxylates
    Tianle Gao, Xiaochao Xia, Kenji Tajima, Takuya Yamamoto, Takuya Isono, Toshifumi Satoh
    Macromolecules, 55, 21, 9373, 9383, American Chemical Society (ACS), 21 Oct. 2022, [Peer-reviewed], [Internationally co-authored], [International Magazine]
    Scientific journal
  • Tailored Solid-State Carbohydrate Nanostructures Based on Star-Shaped Discrete Block Co-Oligomers
    Takuya Isono, Ryoya Komaki, Nao Kawakami, Kai Chen, Hsin-Lung Chen, Chaehun Lee, Kazushige Suzuki, Brian J. Ree, Hiroaki Mamiya, Takuya Yamamoto, Redouane Borsali, Kenji Tajima, Toshifumi Satoh
    Biomacromolecules, 23, 9, 3978, 3989, American Chemical Society (ACS), 12 Sep. 2022
    Scientific journal
  • Fabrication of Ultrafine, Highly Ordered Nanostructures using Carbohydrate-inorganic Hybrid Block Copolymers
    Nishimura, T, Katsuhara, S, Lee, C, Ree, B. J, Borsali, R, Yamamoto, T, Tajima, K, Satoh, T, Isono, T
    Nanomaterials, 12, 10, 1653, 1653, MDPI AG, May 2022, [Peer-reviewed]
    Scientific journal, Block copolymers (BCPs) have garnered considerable interest due to their ability to form microphase-separated structures suitable for nanofabrication. For these applications, it is critical to achieve both sufficient etch selectivity and a small domain size. To meet both requirements concurrently, we propose the use of oligosaccharide and oligodimethylsiloxane as hydrophilic and etch-resistant hydrophobic inorganic blocks, respectively, to build up a novel BCP system, i.e., carbohydrate-inorganic hybrid BCP. The carbohydrate-inorganic hybrid BCPs were synthesized via a click reaction between oligodimethylsiloxane with an azido group at each chain end and propargyl-functionalized maltooligosaccharide (consisting of one, two, and three glucose units). In the bulk state, small-angle X-ray scattering revealed that these BCPs microphase separated into gyroid, asymmetric lamellar, and symmetric lamellar structures with domain-spacing ranging from 5.0 to 5.9 nm depending on the volume fraction. Additionally, we investigated microphase-separated structures in the thin film state and discovered that the BCP with the most asymmetric composition formed an ultrafine and highly oriented gyroid structure as well as in the bulk state. After reactive ion etching, the gyroid thin film was transformed into a nanoporous-structured gyroid SiO2 material, demonstrating the material’s promising potential as nanotemplates.
  • Improving the mechanical properties of polycaprolactone using nanofibrillated bacterial cellulose with super long fibers as a filler material
    Hashim, H. b, Emran, N. A. A. b, Isono, T, Katsuhara, S, Ninoyu, H, Matsushima, T, Yamamoto, T, Borsali, R, Satoh, T, Tajima, K
    Composites Part A, May 2022, [Peer-reviewed]
  • Topology- and Sequence-Dependent Micellization and Phase Separation of Pluronic L35, L64, 10R5 and 17R4: Effects of Cyclization and the Chain Ends
    Watanabe, T, Wang, Y, Ono, T, Chimura, S, Isono, T, Tajima, K, Satoh, T, Sato, S, Ida, D, Yamamoto, T
    polymers, 14, 9, 1823, 1823, MDPI AG, Apr. 2022, [Peer-reviewed], [Last author, Corresponding author]
    Scientific journal, The topology effects of cyclization on thermal phase transition behaviors were investigated for a series of amphiphilic Pluronic copolymers of both hydrophilic–hydrophobic–hydrophilic and hydrophobic–hydrophilic–hydrophobic block sequences. The dye solubilization measurements revealed the lowered critical micelle temperatures (TCMT) along with the decreased micellization enthalpy (ΔHmic) and entropy (ΔSmic) for the cyclized species. Furthermore, the transmittance and dynamic light scattering (DLS) measurements indicated a block sequence-dependent effect on the clouding phenomena, where a profound decrease in cloud point (Tc) was only found for the copolymers with a hydrophilic–hydrophobic–hydrophilic block sequence. Thus, the effect of cyclization on these critical temperatures was manifested differently depending on its block sequence. Finally, a comparison of the linear hydroxy-terminated, methoxy-terminated, and cyclized species indicated the effect of cyclization to be unique from a simple elimination of the terminal hydrophilic moieties.
  • Synthesis of hyperbranched polyesters via the ring-opening alternating copolymerisation of epoxides with a cyclic anhydride having a carboxyl group
    Ryota Suzuki, Xiaochao Xia, Tianle Gao, Takuya Yamamoto, Kenji Tajima, Takuya Isono, Toshifumi Satoh
    Polymer Chemistry, 13, 38, 5469, 5477, Royal Society of Chemistry (RSC), 2022
    Scientific journal, Hyperbranched polyesters (HBPEs) are well-known interesting materials used in many fields.
  • Comparative Thermodynamic Studies of the Micellization of Amphiphilic Block Copolymers before and after Cyclization
    Yamamoto, T., Masuda, Y., Tezuka, Y., Korchagina, E., Winnik, F.M.
    Langmuir, 37, in press, 2022, [Peer-reviewed], [Lead author, Corresponding author]
    Scientific journal
  • Development of bio-based elastomer with cellooligosaccaharide derivative as the hard segment
    Satoshi Katsuhara, Yasuko Takagi, Naoki Sunagawa, Kiyohiko Igarashi, Takuya Yamamoto, Kenji Tajima, Takuya Isono, Toshifumi Satoh
    Cellulose Commun., 28, 4, 140, 148, Dec. 2021
    Japanese
  • Topology-Dependent Interaction of Cyclic Poly(ethylene glycol) Complexed with Gold Nanoparticles against Bovine Serum Albumin for a Colorimetric Change
    Onyinyechukwu Justina Oziri, Masatoshi Maeki, Manabu Tokeshi, Takuya Isono, Kenji Tajima, Toshifumi Satoh, Shin-ichiro Sato, Takuya Yamamoto
    Langmuir, American Chemical Society (ACS), Dec. 2021, [Peer-reviewed], [Invited], [Last author, Corresponding author]
    Scientific journal
  • Suzuki–Miyaura Catalyst-Transfer Polycondensation of Triolborate-Type Carbazole Monomers
    Saburo Kobayashi, Mayoh Ashiya, Takuya Yamamoto, Kenji Tajima, Yasunori Yamamoto, Takuya Isono, Toshifumi Satoh
    Polymers, 13, 23, 4168, 4168, MDPI AG, Nov. 2021, [Peer-reviewed]
    Scientific journal, Herein, we report the Suzuki–Miyaura catalyst-transfer polycondensation (SCTP) of triolborate-type carbazole monomers, i.e., potassium 3-(6-bromo-9-(2-octyldodecyl)-9H-carbazole-2-yl)triolborate (M1) and potassium 2-(7-bromo-9-(2-octyldodecyl)-9H-carbazole-2-yl) triolborate (M2), as an efficient and versatile approach for precisely synthesizing poly[9-(2-octyldodecyl)-3,6-carbazole] (3,6-PCz) and poly[9-(2-octyldodecyl)-2,7-carbazole] (2,7-PCz), respectively. The SCTP of triolborate-type carbazole monomers was performed in a mixture of THF/H2O using an initiating system consisted of 4-iodobenzyl alcohol, Pd2(dba)3•CHCl3, and t-Bu3P. In the SCTP of M1, cyclic by-product formation was confirmed, as reported for the corresponding pinacolboronate-type monomer. By optimizing the reaction temperature and reaction time, we successfully synthesized linear end-functionalized 3,6-PCz for the first time. The SCTP of M2 proceeded with almost no side reaction, yielding 2,7-PCz with a functional initiator residue at the α-chain end. Kinetic and block copolymerization experiments demonstrated that the SCTP of M2 proceeded in a chain-growth and controlled/living polymerization manner. This is a novel study on the synthesis of 2,7-PCz via SCTP. By taking advantage of the well-controlled nature of this polymerization system, we demonstrated the synthesis of high-molecular-weight 2,7-PCzs (Mn = 5–38 kg mol−1) with a relatively narrow ÐM (1.35–1.48). Furthermore, we successfully synthesized fluorene/carbazole copolymers as well as 2,7-PCz-containing diblock copolymers, demonstrating the versatility of the present polymerization system as a novel synthetic strategy for well-defined polycarbazole-based materials.
  • PEGylation of Silver Nanoparticles by Physisorption of Cyclic Poly(Ethylene Glycol) for Enhanced Dispersion Stability, Antimicrobial Activity, and Cytotoxicity
    Onyinyechukwu Oziri, Yubo Wang, Tomohisa Watanabe, Shuya Uno, Masatoshi Maeki, Manabu Tokeshi, Takuya Isono, Kenji Tajima, Toshifumi Satoh, Shin-ichiro Sato, Yutaka Miura, Takuya Yamamoto
    Nanoscale Advances, 4, 2, 532, 545, Royal Society of Chemistry (RSC), Nov. 2021, [Peer-reviewed], [Last author, Corresponding author]
    English, Scientific journal, Silver nanoparticles (AgNPs) are practically valuable in biological applications. However, no steady PEGylation has been established, which is essential for internal use in humans or animals. In this study, cyclic...
  • Densely arrayed cage-shaped polymer topologies synthesized via cyclopolymerization of star-shaped macromonomers
    Mato, Y, Sudo, M, Marubayashi, H, Ree, B, Tajima, K, Yamamoto, T, Jinnai, H, Isono, T, Satoh, T
    Macromolecules, 54, 19, 9079, 9090, American Chemical Society (ACS), Sep. 2021
    Scientific journal
  • Effect of Hydrogen–Deuterium exchange in amide linkages on properties of electrospun polyamide nanofibers
    Dongyang Li, Wataru Takarada, Minoru Ashizawa, Takuya Yamamoto, Hidetoshi Matsumoto
    Polymer, 123994, 123994, Elsevier BV, Jul. 2021, [Peer-reviewed], [Corresponding author]
    Scientific journal
  • Enhanced Self-Assembly and Mechanical Properties of Cellulose-Based Triblock Copolymers: Comparisons with Amylose-Based Triblock Copolymers
    Katsuhara, S., Takagi, Y., Sunagawa, N., Igarashi, K., Yamamoto, T., Tajima, K., Isono, T., Satoh, T.
    ACS Sustainable Chemistry and Engineering, 9, 29, Jun. 2021
    Scientific journal
  • One‐Shot Intrablock Crosslinking of Linear Diblock Copolymer to Realize Janus‐shaped Single‐Chain Nanoparticle
    Kodai Watanabe, Noya Kaizawa, Brian J. Ree, Takuya Yamamoto, Kenji Tajima, Takuya Isono, Toshifumi Satoh
    Angewandte Chemie International Edition, 60, 33, 18122, 18128, Wiley, 26 May 2021, [Peer-reviewed]
    Scientific journal
  • Cyclization of PEG and Pluronic Surfactants and the Effects of the Topology on Their Interfacial Activity
    Watanabe, Tomohisa, Chimura, Satoru, Wang, Yubo, Ono, Tomoko, Isono, Takuya, Tajima, Kenji, Satoh, Toshifumi, Sato, Shin-ichiro, Ida, Daichi, Yamamoto, Takuya
    Langmuir, 37, 23, 6974, 6984, American Chemical Society (ACS), May 2021, [Peer-reviewed], [Corresponding author]
    Scientific journal
  • Metal-Organic Frameworks for Practical Separation of Cyclic and Linear Polymers
    Sawayama, T., Wang, Y., Watanabe, T., Takayanagi, M., Yamamoto, T., Hosono, N., Uemura, T.
    Angewandte Chemie - International Edition, 60, 21, 11830, 11834, Apr. 2021
    Scientific journal
  • Dispersion Stabilization of Gold Nanoparticles Using Cyclic Poly(Ethylene Glycol)               
    Tomohisa Watanabe, Yubo Wang, Takuya Yamamoto
    The Bulletin of the Nano Science and Technology, Mar. 2021, [Invited], [Last author, Corresponding author]
  • Rapid access to discrete and monodisperse block co-oligomers from sugar and terpenoid toward ultrasmall periodic nanostructures
    Takuya Isono, Ryoya Komaki, Chaehun Lee, Nao Kawakami, Brian J. Ree, Kodai Watanabe, Kohei Yoshida, Hiroaki Mamiya, Takuya Yamamoto, Redouane Borsali, Kenji Tajima, Toshifumi Satoh
    Communications Chemistry, 3, 1, 01 Dec. 2020
    Scientific journal, © 2020, The Author(s). Discrete block co-oligomers (BCOs) are gaining considerable attention due to their potential to form highly ordered ultrasmall nanostructures suitable for lithographic templates. However, laborious synthetic routes present a major hurdle to the practical application. Herein, we report a readily available discrete BCO system that is capable of forming various self-assembled nanostructures with ultrasmall periodicity. Click coupling of propargyl-functionalized sugars (containing 1–7 glucose units) and azido-functionalized terpenoids (containing 3, 4, and 9 isoprene units) afforded the discrete and monodisperse BCOs with a desired total degree of polymerization and block ratio. These BCOs microphase separated into lamellar, gyroid, and cylindrical morphologies with the domain spacing (d) of 4.2–7.5 nm. Considering easy synthesis and rich phase behavior, presented BCO systems could be highly promising for application to diverse ~4-nm nanofabrications.
  • Enhanced dispersion stability of gold nanoparticles by the physisorption of cyclic poly(ethylene glycol)
    Yubo Wang, Jose Enrico Q. Quinsaat, Tomoko Ono, Masatoshi Maeki, Manabu Tokeshi, Takuya Isono, Kenji Tajima, Toshifumi Satoh, Shin ichiro Sato, Yutaka Miura, Takuya Yamamoto
    Nature Communications, 11, 1, Dec. 2020
    Scientific journal, © 2020, The Author(s). Nano-sized metal particles are attracting much interest in industrial and biomedical applications due to the recent progress and development of nanotechnology, and the surface-modifications by appropriate polymers are key techniques to stably express their characteristics. Herein, we applied cyclic poly(ethylene glycol) (c-PEG), having no chemical inhomogeneity, to provide a polymer topology-dependent stabilization for the surface-modification of gold nanoparticles (AuNPs) through physisorption. By simply mixing c-PEG, but not linear counterparts, enables AuNPs to maintain dispersibility through freezing, lyophilization, or heating. Surprisingly, c-PEG endowed AuNPs with even better dispersion stability than thiolated PEG (HS–PEG–OMe). The stronger affinity of c-PEG was confirmed by DLS, ζ-potential, and FT-IR. Furthermore, the c-PEG system exhibited prolonged blood circulation and enhanced tumor accumulation in mice. Our data suggests that c-PEG induces physisorption on AuNPs, supplying sufficient stability toward bio-medical applications, and would be an alternative approach to the gold–sulfur chemisorption.
  • Programmed folding into spiro-multicyclic polymer topologies from linear and star-shaped chains
    Yoshinobu Mato, Kohei Honda, Brian J. Ree, Kenji Tajima, Takuya Yamamoto, Tetsuo Deguchi, Takuya Isono, Toshifumi Satoh
    Communications Chemistry, 3, 1, Springer Science and Business Media LLC, Dec. 2020, [Peer-reviewed]
    Scientific journal
  • Suzuki-Miyaura catalyst-transfer polycondensation of triolborate-type fluorene monomer: Toward rapid access to polyfluorene-containing block and graft copolymers from various macroinitiators
    Saburo Kobayashi, Kaiyu Fujiwara, Dai Hua Jiang, Takuya Yamamoto, Kenji Tajima, Yasunori Yamamoto, Takuya Isono, Toshifumi Satoh
    Polymer Chemistry, 11, 42, 6832, 6839, 14 Nov. 2020
    Scientific journal, © The Royal Society of Chemistry. In this study, we demonstrated that the Suzuki-Miyaura catalyst transfer polycondensation (SCTP) of the triolborate-type fluorene monomer, viz. potassium 2-(7-bromo-9,9-dihexyl-9H-fluorene-2-yl)triolborate, can be an efficient and versatile approach to the precise synthesis of poly[2,7-(9,9-dihexylfluorene)]s (PFs) and PF-containing block and graft copolymers. SCTP of the triolborate-type monomer proceeded rapidly in a THF/H2O mixed solvent at -10 °C using an iodobenzene derivative/Pd2(dba)3·CHCl3/t-Bu3P initiating system. Kinetic and post-polymerization experiments revealed that SCTP proceeded via the chain-growth and living polymerization mechanisms. The most important feature of the present polymerization system is that only a small amount of base and water can sufficiently promote the reaction. The well-controlled nature of this polymerization system enabled the synthesis of high-molecular-weight PFs (Mn = 5-69 kg mol-1) with narrow dispersity (ĐM = 1.14-1.38) and α-end-functionalized PFs. Most importantly, PF-containing block and graft copolymers were successfully synthesized, beginning with various iodobenzene-functionalized macroinitiators; this was difficult to achieve by the conventional SCTP of pinacolboronate-type fluorene monomer. One of the key factors for the successful block and graft copolymer syntheses is the reduced water content in the polymerization medium, which suppressed the potential precipitation/aggregation of the macroinitiators.
  • An organocatalytic ring-opening polymerization approach to highly alternating copolymers of lactic acid and glycolic acid
    Kaoru Takojima, Hiroshi Makino, Tatsuya Saito, Takuya Yamamoto, Kenji Tajima, Takuya Isono, Toshifumi Satoh
    Polymer Chemistry, 11, 39, 6365, 6373, 21 Oct. 2020
    Scientific journal, © The Royal Society of Chemistry. The alternating copolymer of lactic acid and glycolic acid (PLGA) is a highly promising next generation biodegradable material for biomedical and pharmaceutical applications due to its uniform degradation behaviors in addition to its ability to form stereocomplexes. However, versatile synthetic methods toward the narrowly dispersed alternating PLGAs with controlled molecular weights and desired end functionalities have been largely unexplored. Herein, we report the organocatalytic regioselective ring-opening polymerization (ROP) of optically active methylglycolides (l- and d-MGs) to produce highly alternating PLGAs. The ROP of l-MG using a phosphazene base P2-t-Bu/alcohol system in THF at -78 °C achieved the highest regioselectivity (P = 0.95) as well as a good control over the molecular weight (Mn = 6.6-15.6 g mol-1), with a relatively narrow dispersity (Đ = 1.21-1.29). Furthermore, alternating PLGA diol as well as azido-, ethynyl-, and poly(ethylene glycol) monomethyl ether-end-functionalized alternating PLGAs was successfully obtained by employing the corresponding functional alcohol initiators. An enantiomeric 1 : 1 blend of PLGAs prepared from l- and d-MGs formed a stereocomplex with a crystallinity and melting point comparable to the reported data for the stereocomplex from the perfectly alternating PLGAs produced via a polycondensation approach, which implies the high degree of the alternating sequence of the obtained copolymers.
  • Carbohydrates as Hard Segments for Sustainable Elastomers: Carbohydrates Direct the Self-Assembly and Mechanical Properties of Fully Bio-Based Block Copolymers
    Takuya Isono, Saki Nakahira, Hui-Ching Hsieh, Satoshi Katsuhara, Hiroaki Mamiya, Takuya Yamamoto, Wen-Chang Chen, Redouane Borsali, Kenji Tajima, Toshifumi Satoh
    Macromolecules, 53, 13, 5408, 5417, American Chemical Society (ACS), 16 Jun. 2020, [Peer-reviewed]
    Scientific journal
  • Self-Assembly of Linear and Cyclic Polylactide Stereoblock Copolymers with a Parallel and Antiparallel Chain Arrangement Distinguishing Their Directions on a Water Surface
    Kenta Iwashima, Takuya Yamamoto, Yasuyuki Tezuka, Jiro Kumaki
    Langmuir, 36, 22, 6216, 6221, American Chemical Society (ACS), 09 Jun. 2020, [Peer-reviewed], [International Magazine]
    English, Scientific journal, The self-assembly of molecules into a well-ordered structure is one of the most important processes in fabricating sophisticated materials. Here, we show that polymer chains can be self-assembled, distinguishing their direction (parallel or antiparallel), and could be a new useful scaffold for self-assembly in a controlled direction. The system that was used was a stereocomplex (SC) formation of linear and cyclic polylactide (PLA) stereoblock copolymers with a parallel and antiparallel chain arrangement in a Langmuir monolayer. The linear and cyclic stereoblock copolymers with a parallel arrangement formed a well-ordered lamellar SC in the first and second layers upon compression, but the linear and cyclic stereoblock copolymers with an antiparallel arrangement did not form a first-layer lamella and instead formed only the second-layer lamella. These results were only rationally explained by assuming that the enantiomeric PLA chains selectively assembled in a parallel direction, not in an antiparallel direction, in the SC. A simple polymer chain could be self-assembled, distinguishing the direction without a specific interaction group in it.
  • Direct Synthesis of Chain‐end‐functionalized Poly(3‐hexylthiophene) without Protecting Groups Using a Zincate Complex
    Shin Inagaki, Takuya Yamamoto, Tomoya Higashihara
    Macromolecular Rapid Communications, 41, 11, 2000148, 2000148, Wiley, Jun. 2020, [Peer-reviewed], [International Magazine]
    English, Scientific journal, Chain-end-functionalized poly(3-hexylthiophene)s (P3HTs) with benzyl alcohol (─PhCH2 OH), phenol (─PhOH), and benzoic acid (─PhCOOH) groups are directly synthesized based on the Negishi catalyst-transfer polycondensation method utilizing the zincate complex of t Bu4 ZnLi2 . In this system, neither protection nor deprotection steps are required, and also providing a living polymerization system to control the molecular weight while maintaining a low molar mass dispersity (ÐM ) of the obtained P3HT derivatives. Indeed, the chain-end-functionalized P3HTs can be synthesized along with controlled number-average molecular weights (Mn = 5100-20 000), low ÐM (1.06-1.14), and high chain-end functionality (Fn = 46-86%). The Fn values for the alcohol and phenol groups are found to be high (86% for ─PhCH2 OH and 71% for ─PhOH based on 1 H NMR, respectively), as also confirmed by matrix-assisted laser desorption/ionization time of flight mass spectroscopy. The easily synthesizable chain-end-functionalized P3HTs will be applicable for the facile synthesis of block and branched polymers containing P3HT as well as its related semiconducting polymer segments.
  • Detailed Structural Analyses of Nanofibrillated Bacterial Cellulose and Its Application as Binder Material for a Display Device
    Kenji Tajima, Koutaro Tahara, Junya Ohba, Ryo Kusumoto, Ryota Kose, Hiroyuki Kono, Tokuo Matsushima, Koji Fushimi, Takuya Isono, Takuya Yamamoto, Toshifumi Satoh
    BIOMACROMOLECULES, 21, 2, 581, 588, AMER CHEMICAL SOC, Feb. 2020, [Peer-reviewed]
    English, Scientific journal, Nanofibrillated bacterial cellulose (NFBC) is produced by culturing a cellulose-producing bacterium under agitated aerobic conditions in a carboxymethylcellulose (CMC)-supplemented medium. Detailed structural analyses revealed that NFBC fiber widths varied with the degree of substitution of the CMC used, and zeta potential values decreased with the increment of CMC concentration in the medium. Transmission electron microscopy observation after immunostaining demonstrated that CMC molecules were present on the NFBC microfibril surfaces. We tested NFBC for utility as a binder for a display device that uses electrochromic (EC) material. Introduction of a quaternary ammonium group into the EC molecules enhanced their interactions with the negatively charged NFBC microfibrils. A casting process homogeneously adsorbed the EC molecules onto the surface of a transparent electrode with NFBC. A homogeneous color change was successfully observed upon applying an electric field, suggesting that NFBC could be used as a binder material for uniform surface adsorption.
  • Highly Asymmetric Lamellar Nanostructures from Nanoparticle−Linear Hybrid Block Copolymers
    Kodai Watanabe, Satoshi Katsuhara, Hiroaki Mamiya, Yukihiko Kawamura, Takuya Yamamoto, Kenji Tajima, Takuya Isono, Toshifumi Satoh
    Nanoscale, Royal Society of Chemistry (RSC), 2020, [Peer-reviewed]
    Scientific journal,

    Highly asymmetric lamellar (A-LAM) nanostructure is one of the most important template geometries for block copolymer (BCP) lithography. However, A-LAM is unattainable from conventional BCPs, and there is no general...

  • Metallopolymer-block-oligosaccharide for sub-10 nm microphase separation
    Satoshi Katsuhara, Hiroaki Mamiya, Takuya Yamamoto, Kenji Tajima, Takuya Isono, Toshifumi Satoh
    Polymer Chemistry, Royal Society of Chemistry ({RSC}), 2020, [Peer-reviewed]
    Scientific journal
  • Facile synthesis of poly(trimethylene carbonate) by alkali metal carboxylate-catalyzed ring-opening polymerization
    Kaoru Takojima, Tatsuya Saito, Cedric Vevert, Viko Ladelta, Panayiotis Bilalis, Jun Watanabe, Shintaro Hatanaka, Takashi Konno, Takuya Yamamoto, Kenji Tajima, Nikos Hadjichristidis, Takuya Isono, Toshifumi Satoh
    Polymer Journal, 52, 1, 103, 110, NATURE PUBLISHING GROUP, 01 Jan. 2020, [Peer-reviewed]
    English, Scientific journal, © 2019, The Society of Polymer Science, Japan. Abstract: Alkali metal carboxylates, including sodium acetate, sodium benzoate, and sodium sorbate, which are all readily available and widely used as food additives, were found to promote the ring-opening polymerization (ROP) of trimethylene carbonate (TMC) to produce poly(trimethylene carbonate) (PTMC). The sodium acetate-catalyzed ROP of TMC proceeded in the presence of an alcohol initiator under solvent-free conditions at 70 °C, even at very low catalyst loadings of 0.01–0.0001 mol%. The controlled nature of this ROP system enabled the synthesis of PTMCs with predicted molecular weights ranging from 2400 to 11 700 g mol−1 and narrow dispersities (~1.23). Importantly, ROP is initiated by an alcohol initiator, allowing PTMC production with desired functional groups, such as azido, alkyne, and methacrylate groups, at the α-chain end. Furthermore, the poly(l-lactic acid)-b-PTMC-b-poly(l-lactic acid) triblock copolymer, a biodegradable thermoplastic elastomer, was successfully synthesized in one pot via the sodium acetate-catalyzed ring-opening block copolymerization of TMC and l-lactide with a 1,3-propanediol initiator.
  • Progress of Cyclic Polymer Synthesis and Potentials to Functional Materials               
    Yamamoto Takuya
    Kobunshi, 68, 613, 617, Nov. 2019, [Peer-reviewed], [Invited]
    Japanese, Scientific journal
  • Installing a functional group into the inactive ω-chain end of PMMA and PS-: B -PMMA by terminal-selective transesterification
    Yoshida, K., Yamamoto, T., Tajima, K., Isono, T., Satoh, T.
    Polymer Chemistry, 10, 24, 3390, 3398, Jun. 2019, [Peer-reviewed]
    English, Scientific journal
  • Programmed Polymer Folding with Periodically Positioned Tetrafunctional Telechelic Precursors by Cyclic Ammonium Salt Units as Nodal Points
    Kyoda, K., Yamamoto, T., Tezuka, Y.
    Journal of the American Chemical Society, 141, 18, 7526, 7536, 08 May 2019, [Peer-reviewed]
    Scientific journal
  • Trimethyl Glycine as an Environmentally Benign and Biocompatible Organocatalyst for Ring-Opening Polymerization of Cyclic Carbonate
    Tatsuya Saito, Kaoru Takojima, Takafumi Oyama, Shintaro Hatanaka, Takashi Konno, Takuya Yamamoto, Kenji Tajima, Takuya Isono, Toshifumi Satoh
    ACS Sustainable Chemistry & Engineering, 7, 9, 8868, 8875, American Chemical Society (ACS), 06 May 2019, [Peer-reviewed]
    Scientific journal
  • Downsizing feature of microphase-separated structures via intramolecular crosslinking of block copolymers.
    Kodai Watanabe, Satoshi Katsuhara, Hiroaki Mamiya, Takuya Yamamoto, Kenji Tajima, Takuya Isono, Toshifumi Satoh
    Chemical science, 10, 11, 3330, 3339, 21 Mar. 2019, [Peer-reviewed], [International Magazine]
    English, Scientific journal, A novel strategy for downsizing the feature of microphase-separated structures was developed via the intramolecular crosslinking reaction of block copolymers (BCPs) without changing the molecular weight. A series of BCPs consisting of poly[styrene-st-(p-3-butenyl styrene)] and poly(rac-lactide) (SBS-LA) was subjected to Ru-catalyzed olefin metathesis under highly diluted conditions to produce intramolecularly crosslinked BCPs (SBS(cl)-LAs). Small-angle X-ray scattering measurement and transmission electron microscopy observation of the SBS(cl)-LAs revealed feature size reduction in lamellar (LAM) and hexagonally close-packed cylinder (HEX) structures in the bulk state, which was surely due to the restricted chain dimensions of the intramolecularly crosslinked SBS block. Notably, the degree of size reduction was controllable by varying the crosslink density, with a maximum decrease of 22% in the LAM spacing. In addition, we successfully observed the downsizing of the HEX structure in the thin film state using atomic force microscopy, indicating the applicability of the present methodology to next-generation lithography technology.
  • Microphase separation of carbohydrate-based star-block copolymers with sub-10 nm periodicity
    Isono, T., Kawakami, N., Watanabe, K., Yoshida, K., Otsuka, I., Mamiya, H., Ito, H., Yamamoto, T., Tajima, K., Borsali, R., Satoh, T.
    Polymer Chemistry, 10, 9, 1119, 1129, 07 Mar. 2019, [Peer-reviewed]
    Scientific journal
  • A versatile synthetic strategy for macromolecular cages: intramolecular consecutive cyclization of star-shaped polymers.
    Yoshinobu Mato, Kohei Honda, Kenji Tajima, Takuya Yamamoto, Takuya Isono, Toshifumi Satoh
    Chemical science, 10, 2, 440, 446, 14 Jan. 2019, [Peer-reviewed], [International Magazine]
    English, Cage-shaped polymers, or "macromolecular cages", are of great interest as the macromolecular analogues of molecular cages because of their various potential applications in supramolecular chemistry and materials science. However, the systematic synthesis of macromolecular cages remains a great challenge. Herein, we describe a robust and versatile synthetic strategy for macromolecular cages with defined arm numbers and sizes based on the intramolecular consecutive cyclization of highly reactive norbornene groups attached to each end of the arms of a star-shaped polymer precursor. The cyclizations of three-, four-, six-, and eight-armed star-shaped poly(ε-caprolactone)s (PCLs) bearing a norbornenyl group at each arm terminus were effected with Grubbs' third generation catalyst at high dilution. 1H NMR, SEC, and MALDI-TOF MS analyses revealed that the reaction proceeded to produce the desired macromolecular cages with sufficient purity. The molecular sizes of the macromolecular cages were controlled by simply changing the molecular weight of the star-shaped polymer precursors. Systematic investigation of the structure-property relationships confirmed that the macromolecular cages adopt a much more compact conformation, in both the solution and bulk states, as compared to their linear and star-shaped counterparts. This synthetic approach marks a significant advance in the synthesis of complex macromolecular architectures and provides a platform for novel applications using cage-shaped molecules with polymer frameworks.
  • Micelle Structure Details and Stabilities of Cyclic Block Copolymer Amphiphile and Its Linear Analogues
    Ree Brian J, Satoh Toshifumi, Yamamoto Takuya
    POLYMERS, 11, 1, MDPI, Jan. 2019, [Peer-reviewed]
    English, Scientific journal, In this study, we investigate structures and stabilities of the micelles of a cyclic amphiphile (c-PBA-b-PEO) composed of poly(n-butyl acrylate) (PBA) and poly(ethylene oxide) (PEO) blocks and its linear diblock and triblock analogues (l-PBA-b-PEO and l-PBA-b-PEO-b-PBA) by using synchrotron X-ray scattering and quantitative data analysis. The comprehensive scattering analysis gives details and insights to the micellar architecture through structural parameters. Furthermore, this analysis provides direct clues for structural stabilities in micelles, which can be used as a good guideline to design highly stable micelles. Interestingly, in water, all topological polymers are found to form ellipsoidal micelles rather than spherical micelles; more interestingly, the cyclic polymer and its linear triblock analog make oblate-ellipsoidal micelles while the linear diblock analog makes a prolate-ellipsoidal micelle. The analysis results collectively inform that the cyclic topology enables more compact micelle formation as well as provides a positive impact on the micellar structural integrity.
  • Synthesis and Unimolecular ESA-CF Polymer Cyclization of Zwitterionic Telechelic Precursors
    Konomoto, T., Nakamura, K., Yamamoto, T., Tezuka, Y.
    Macromolecules, 52, 23, 9208, 9219, 2019, [Peer-reviewed]
    English, Scientific journal
  • Synthesis, Isolation, and Properties of All Head-to-Tail Cyclic Poly(3-hexylthiophene): Fully Delocalized Exciton over the Defect-Free Ring Polymer
    Yamamoto Takuya, Hosokawa Masaaki, Nakamura Minato, Sato Shin-ichiro, Isono Takuya, Tajima Kenji, Satoh Toshifumi, Sato Masamichi, Tezuka Yasuyuki, Saeki Akinori, Kikkawa Yoshihiro
    MACROMOLECULES, 51, 22, 9284, 9293, American Chemical Society (ACS), 27 Nov. 2018, [Peer-reviewed]
    Scientific journal
  • Chain-End Functionalization with a Saccharide for 10 nm Microphase Separation: "classical" PS- b-PMMA versus PS- b-PMMA-Saccharide
    Yoshida, K., Tanaka, S., Yamamoto, T., Tajima, K., Borsali, R., Isono, T., Satoh, T.
    Macromolecules, 51, 21, 8870, 8877, 13 Nov. 2018, [Peer-reviewed]
    Scientific journal
  • Topology effects of cyclic polymers: Controlling the topology for innovative functionalities
    Yamamoto, T.
    Reactive and Functional Polymers, 132, 43, 50, Nov. 2018, [Peer-reviewed]
    Scientific journal
  • Facile and Efficient Modification of Polystyrene- block-poly(methyl methacrylate) for Achieving Sub-10 nm Feature Size
    Yoshida, K., Tian, L., Miyagi, K., Yamazaki, A., Mamiya, H., Yamamoto, T., Tajima, K., Isono, T., Satoh, T.
    Macromolecules, 51, 20, 8064, 8072, 23 Oct. 2018, [Peer-reviewed]
    Scientific journal
  • Synthesis of μ-ABC Tricyclic Miktoarm Star Polymer via Intramolecular Click Cyclization.
    Tomoki Shingu, Takuya Yamamoto, Kenji Tajima, Takuya Isono, Toshifumi Satoh
    Polymers, 10, 8, 06 Aug. 2018, [Peer-reviewed], [International Magazine]
    English, Cyclic polymers exhibit unique physical and chemical properties because of the restricted chain mobility and absence of chain ends. Although many types of homopolymers and diblock copolymers possessing cyclic architectures have been synthesized to date, there are relatively few reports of cyclic triblock terpolymers because of their synthetic difficulties. In this study, a novel synthetic approach for μ-ABC tricyclic miktoarm star polymers involving t-Bu-P₄-catalyzed ring-opening polymerization (ROP) of glycidyl ethers and intramolecular copper-catalyzed azido-alkyne cycloaddition (CuAAC) was developed. First, the t-Bu-P₄-catalyzed ROP of decyl glycidyl ether, dec-9-enyl glycidyl ether, and 2-(2-(2-methoxyethoxy) ethoxy) ethyl glycidyl ether with the aid of functional initiators and terminators was employed for the preparation of a clickable linear triblock terpolymer precursor possessing three azido and three ethynyl groups at the selected positions. Next, the intramolecular CuAAC of the linear precursor successfully produced the well-defined tricyclic triblock terpolymer with narrow dispersity in a reasonable yield. The present strategy is useful for synthesizing model polymers for studying the topological effects on the triblock terpolymer self-assembly.
  • Multicyclic Polymer Synthesis through Controlled/Living Cyclopolymerization of α,ω-Dinorbornenyl-Functionalized Macromonomers
    Takuya Isono, Tetsuya Sasamori, Kohei Honda, Yoshinobu Mato, Takuya Yamamoto, Kenji Tajima, Toshifumi Satoh
    Macromolecules, 51, 10, 3855, 3864, American Chemical Society, 22 May 2018, [Peer-reviewed]
    English, Scientific journal, A novel synthesis of multicyclic polymers that feature ultradense arrays of cyclic polymer units has been developed by exploiting the cyclopolymerization of α,ω-norbornenyl end-functionalized macromonomers mediated by the Grubbs third-generation catalyst (G3). Owing to the living polymerization nature, the number of cyclic repeating units in these multicyclic polymers was controlled to be between 1 and approximately 70 by varying the initial macromonomer-to-G3 ratio. The ring size was also tuned by choosing the molecular weight of the macromonomer
    in this way we successfully prepared multicyclic polymers that possess cyclic repeating units composed of up to about 500 atoms, which by far exceeds those prepared to date by cyclopolymerization. Specifically, cyclopolymerizations of α,ω-norbornenyl end-functionalized poly(l-lactide)s (PLLAs) proceeded homogeneously under highly dilute conditions (∼0.1 mM in CH2Cl2) to give multicyclic polymers that feature cyclic PLLA repeating units on the polynorbornene backbone. The cyclic product architectures were confirmed not only by structural characterization based on NMR, MALDI-TOF MS, and SEC analyses but also by comparing their glass transition temperatures, viscosities, and hydrodynamic radii with their acyclic counterparts. The cyclopolymerization strategy was applicable to a variety of α,ω-norbornenyl end-functionalized macromonomers, such as poly(ϵ-caprolactone), poly(ethylene glycol) (PEG), poly(tetrahydrofuran), and PLLA-b-PEG-b-PLLA. The successful statistical and block cyclocopolymerizations of the PLLA and PEG macromonomers gave amphiphilic multicyclic copolymers.
  • Alkali Metal Carboxylate as an Efficient and Simple Catalyst for Ring-Opening Polymerization of Cyclic Esters
    Tatsuya Saito, Yusuke Aizawa, Takuya Yamamoto, Kenji Tajima, Takuya Isono, Toshifumi Satoh
    Macromolecules, 51, 3, 689, 696, American Chemical Society, 13 Feb. 2018, [Peer-reviewed]
    English, Scientific journal, Alkali metal carboxylates were discovered as efficient and simple catalysts for the ring-opening polymerization of cyclic esters that are alternatives to conventional metal-based catalysts and organocatalysts. In our system using an alcohol initiator and this simple catalyst, biodegradable and biocompatible aliphatic polyesters, such as poly(lactide), poly(e-caprolactone), poly(δ-valerolactone), and poly(trimethylene carbonate), were obtained with predictive molecular weights ranging from 3500 to 22-600 and narrow dispersities. A kinetic experiment for the ROP of l-lactide confirmed the controlled/living nature of the present ROP system, which allowed the precise synthesis of end-functionalized polyesters as well as multihydroxyl-containing polyesters, including α,hydroxy telechelic and star-shaped polyesters. Furthermore, a block copolymer containing the poly(l-lactide) segment was successfully synthesized using a macroinitiator possessing a hydroxyl group at the chain end. The tunability of the alkali metal carboxylates by the appropriate choice of the alkyl moiety and countercation enables not only control of the polymerization behavior but also expansion of the scope of the applicable monomers. Given the low cost, easy handling, and low toxicity of the alkali metal carboxylates, the present ROP system can be highly promising for both laboratory- and industrial-scale polyester productions.
  • Load-induced frictional transition for well-defined cyclic self-Assembled monolayers
    Shundo, A., Yamamoto, T., Tezuka, Y., Tanaka, K.
    Toraibarojisuto/Journal of Japanese Society of Tribologists, 63, 4, 248, 252, 01 Jan. 2018
    Scientific journal, © 2018 Japanese Society of Tribologists. All rights reserved. Self-Assembled monolayer (SAM) with amphiphilic linear molecules has been studied as a surface modifier. In general, the surface properties of a SAM are dependent on the chain end chemistry of the molecules. Thus, a SAM composed of alkane loops from cyclic alkanedisulfide on a gold substrate, in which both sulfurs arc bound to gold, may possess unique surface properties due to the chain folding as well as a lack of chain ends. We here focus on the frictional properties of the linear and cyclic SAMs. For the cyclic SAM, the load dependence of the frictional force became more striking beyond a threshold. Such a frictional transition was not observed for the corresponding linear SAM. The load-induced transition in the frictional response from the alkane loops could be related to the conformational change of the alkane loops, which collapsed along the direction normal to the SAM surface.
  • 環状自己組織化単分子膜の荷重誘起表面摩擦転移               
    春藤淳臣, 山本拓矢, 手塚育志, 田中敬二
    J. Jpn. Soc. Tribol., 63, 248, 252, 2018, [Peer-reviewed], [Invited]
    Japanese, Scientific journal
  • Macrocyclic poly(: P -phenylenevinylene)s by ring expansion metathesis polymerisation and their characterisation by single-molecule spectroscopy
    Benjamin John Lidster, Shuzo Hirata, Shoki Matsuda, Takuya Yamamoto, Venukrishnan Komanduri, Dharam Raj Kumar, Yasuyuki Tezuka, Martin Vacha, Michael L. Turner
    Chemical Science, 9, 11, 2934, 2941, Royal Society of Chemistry, 2018, [Peer-reviewed]
    English, Scientific journal, Ring expansion metathesis polymerisation (REMP) has proven to be a viable approach to prepare high purity cyclic polymers. Macrocyclic polymers with a fully conjugated defect free backbone are of particular interest as these polymers have no end groups that can act as charge traps. In this work soluble macrocyclic poly(p-phenylenevinylene)s (cPPVs) have been prepared directly via the REMP of substituted paracyclophanedienes. Single-molecule spectroscopy of the two topological forms of PPV i.e., linear (lPPV) and cyclic (cPPV) revealed that lPPV exists in an extended conformation whereas the cPPV adopts a restricted ring-like conformation. Despite such large differences in the chain conformation, the spectral properties of the two compounds are unexpectedly very similar, and are dominated by torsional deformations in relatively short conjugated segments.
  • One-Step Production of Amphiphilic Nanofibrillated Cellulose Using a Cellulose-Producing Bacterium
    Kenji Tajima, Ryo Kusumoto, Ryota Kose, Hiroyuki Kono, Tokuo Matsushima, Takuya Isono, Takuya Yamamoto, Toshifumi Satoh
    BIOMACROMOLECULES, 18, 10, 3432, 3438, AMER CHEMICAL SOC, Oct. 2017, [Peer-reviewed]
    English, Scientific journal, Nanofibrillated bacterial cellulose (NFBC) is produced by culturing a cellulose-producing bacterium (Gluconacetobacter intermedius NEDO-01) with rotation or agitation in medium supplemented with carboxymethylcellulose (CMC). Despite a high yield and dispersibility in water, the product immediately aggregates in organic solvents. To broaden its applicability, we prepared amphiphilic NFBC by culturing strain NEDO-01 in medium supplemented with hydroxyethylcellulose or hydroxypropylcellulose instead of CMC. Transmission electron microscopy analysis revealed that the resultant materials (HE-NFBC and HP-NFBC, respectively) comprised relatively uniform fibers with 'diameters of 33 +/- 7 and 42 +/- 8 nm, respectively. HP-NFBC was dispersible in polar organic solvents such as methanol, acetone, isopropyl alcohol, acetonitrile, tetrahydrofuran (THF), and dimethylformamide, and was also dispersible in poly(methyl methacrylate) (PMMA) by solvent mixing using THF. HP-NFBC/PMMA composite films were highly transparent and had a higher tensile strength than neat PMMA film. Thus, HP-NFBC has a broad range of applications, including as a filler material.
  • A Twisting Ring Polymer: Synthesis and Thermally Induced Chiroptical Responses of a Cyclic Poly(tetrahydrofuran) Having Axially Chiral Units
    Satoshi Honda, Kaoru Adachi, Takuya Yamamoto, Yasuyuki Tezuka
    MACROMOLECULES, 50, 14, 5323, 5331, AMER CHEMICAL SOC, Jul. 2017, [Peer-reviewed]
    English, Scientific journal, A series of cyclic poly(tetrahydrofuran)s, poly(THF)s, having, a pair of stereoisomeric forms of axially chiral, 2,2'-disubstituted-1,1'1-binaphthyl (BiNap) unit at the opposite positions, CR-R, CR-S, and CR-R/S, have been newly synthesized through an electrostatic self-assembly and covalent fixation (ESA-CF) process by using a center-functionalized (kentro-telechelic) poly(THF) having an axially chiral BiNap unit and N-phenylpyrrolidinium salt end groups, carrying a dicarboxylate counteranion having a BiNap unit. The relevant cyclic and linear analogues, having one axially chiral unit, C-R (CR-1 and CR-2) and L-R, respectively, have also been prepared according to the ESA-CF protocol. The subsequent CD measurements of these cyclic and linear polymers having axially chiral units by lowering the temperature toward -10 degrees C in hexane revealed the noticeable reduction of the dihedral angle of the binaphthyl units exclusively for the cyclic CR-R as well as for the CR-1 and CR-R/s. The observed thermally induced cyclic topology effect on this chiroptical response is reasoned by the solvophobic interaction promoted for the topologically constrained, looped poly(THF) segments in the vicinity of the BiNap units.
  • A facile strategy for manipulating micellar size and morphology through intramolecular cross-linking of amphiphilic block copolymers
    Ryoto Tanaka, Kodai Watanabe, Takuya Yamamoto, Kenji Tajima, Takuya Isono, Toshifumi Satoh
    POLYMER CHEMISTRY, 8, 23, 3647, 3656, ROYAL SOC CHEMISTRY, Jun. 2017, [Peer-reviewed]
    English, Scientific journal, The effect of intramolecular cross-linking in an amphiphilic block copolymer (BCP) system was systematically investigated in terms of its thermal properties, critical micelle concentration (CMC), and aqueous self-assembly. A series of linear BCPs consisting of poly(ethylene glycol) (PEG) as a hydrophilic block and poly(epsilon-caprolactone-co-7-allyloxepan-2-one) (P(CL-co-ACL)) as a hydrophobic block were prepared by the ring-opening copolymerization of epsilon-caprolactone (CL) and 7-allyloxepan-2-one (ACL) using poly (ethylene glycol) monomethyl ether as an initiator. The intramolecular olefin metathesis reaction in the P(CL-co-ACL) block was subsequently carried out under various conditions to prepare the cross-linked BCPs with different degrees of cross-linking. The thermal analysis confirmed that the linear P(CL-co-ACL) block was found to crystallize, while the cross-linked one showed no crystallinity. In addition, glass transition temperature of the P(CL-co-ACL) block increased upon cross-linking. On the other hand, the intramolecular cross-linking had no significant influence on the CMC. The self-assembled micelles were prepared from the obtained BCPs and their size and morphology were investigated. For the BCPs with relatively short PEG chains, the micellar size decreased from 36.6 nm to 16.7 nm as the degree of cross-linking of the P(CL-co-ACL) block increased. On the other hand, the BCPs with relatively long PEG chains showed a change in the micellar morphology from spherical micelles to short worm and large compound micelles upon cross-linking.
  • Load-Induced Frictional Transition at a Well-Defined Alkane Loop Surface
    Atsuomi Shundo, Koichiro Hori, Yasuyuki Tezuka, Takuya Yamamoto, Keiji Tanaka
    LANGMUIR, 33, 9, 2396, 2401, AMER CHEMICAL SOC, Mar. 2017, [Peer-reviewed]
    English, Scientific journal, Self-assembled monolayers (SAMs) have attracted considerable attention as a tool to confer desirable properties on material surfaces. So far, molecules used for the SAM formation are generally limited to linear ones and thus chain ends dominate the surface properties. In this study, we have successfully demonstrated unique frictional properties of a SAM composed of alkane loops from cyclic alkanedisulfide on a gold substrate, where both sulfurs are bound to gold. The frictional response was proportional to the load. However, once the load went beyond a threshold value, the frictional response became more dominant. Such a frictional transition was reversible and repeatable and was not discerned for a corresponding SAM composed of n-alkyl chains. The load-induced change in the frictional response from the alkane loops could be associated with the conformational change of the alkane loops. The present results differ from most studies, in which the surface properties are designed on the basis of functional chain end groups.
  • Synthesis of Well-Defined Three- and Four-Armed Cage-Shaped Polymers via "Topological Conversion" from Trefoil- and Quatrefoil-Shaped Polymers
    Yusuke Satoh, Hirohiko Matsuno, Takuya Yamamoto, Kenji Tajima, Takuya Isono, Toshifumi Satoh
    MACROMOLECULES, 50, 1, 97, 106, AMER CHEMICAL SOC, Jan. 2017, [Peer-reviewed]
    English, Scientific journal, This paper describes a novel synthetic approach for three- and four-armed cage-shaped polymers based on the topological conversion of the corresponding trefoil- and quatrefoil-shaped precursors. The trefoil- and quatrefoil-shaped polymers were synthesized by the following three reaction steps: (1) the t-Bu-P-4-catalyzed ring-opening polymerization of butylene oxide using multiple hydroxy- and azido-functionalized initiators to produce the three- or four-armed star-shaped polymers possessing three or four azido groups at the focal point, respectively, (2) the omega-end modification to install a propargyl group at each chain end, and (3) the intramolecular multiple click cyclization of the clickable star-shaped precursors. The topological conversion from the trefoil- and quatrefoil-shaped polymers to the cage-shaped polymers was achieved by the catalytic hydrogenolysis of the benzyl ether linkages that had been installed at the focal point. The amphiphilic cage-shaped block copolymers together with the corresponding trefoil- and quatrefoil-shaped counterparts were synthesized in a similar way using 2-(2-(2-methoxyethoxy)ethoxy)ethyl glycidyl ether as a hydrophilic monomer and decyl glycidyl ether as a hydrophobic monomer. Interestingly, significant changes in the critical micelle concentration and micellar morphology were observed for the amphiphilic block copolymers upon the topological conversion from the trefoil- and quatrefoil-shaped to cage-shaped architectures.
  • Formation and Properties of Vesicles from Cyclic Amphiphilic PS-PEO Block Copolymers
    Eisuke Baba, Toshiaki Yatsunami, Yasuyuki Tezuka, Takuya Yamamoto
    LANGMUIR, 32, 40, 10344, 10349, AMER CHEMICAL SOC, Oct. 2016, [Peer-reviewed]
    English, Scientific journal, Linear polystyrene-poly(ethylene oxide)-polystyrene (PS-PEO-PS) block copolymers and corresponding cyclized PS-PEO counterparts with three different PS molecular weights were synthesized and self-assembled to investigate the effects arising from the topology. Linear PS5-PEO45-PS5 (L1) and cyclic PS10-PEO45 (C1) formed micelles. As previously reported for poly(n-butyl acrylate) and PEO block copolymers, the micelles from C1 showed more than 30 degrees C higher phase transition temperature (cloud point, Tc) than those from L1. Linear PS10-PEO45-PS10 (L2) and cyclic PS20-PEO45 (C2) resulted in the formation of a structure called large compound micelles. Self-assembly of linear PS40-PEO48-PS40 (L3) and cyclic PS86-PEO48 (C3) lead to the formation of vesicles. The vesicles were characterized by TEM, DLS, and SLS. Remarkably, the vesicles from L3 (Tc = 69, 59, and 48 degrees C in the presence of 1, 5, and 10 wt % of NaCl, respectively) were found to be somewhat more thermally stable than those from C3 (Tc = 62, 52, and 43 degrees C in the presence of 1, 5, and 10 wt % of NaCl, respectively). This trend of the thermal stability was counterintuitively opposed to the case of the micelles. Moreover, Tc of the vesicles was controlled by the ratio of L3 and C3.
  • Synthesis of Cyclic Polymers and Characterization of Their Diffusive Motion in the Melt State at the Single Molecule Level
    Satoshi Habuchi, Takuya Yamamoto, Yasuyuki Tezuka
    JOVE-JOURNAL OF VISUALIZED EXPERIMENTS, 115, JOURNAL OF VISUALIZED EXPERIMENTS, Sep. 2016, [Peer-reviewed]
    English, Scientific journal, We demonstrate a method for the synthesis of cyclic polymers and a protocol for characterizing their diffusive motion in a melt state at the single molecule level. An electrostatic self-assembly and covalent fixation (ESA-CF) process is used for the synthesis of the cyclic poly(tetrahydrofuran) (poly(THF)). The diffusive motion of individual cyclic polymer chains in a melt state is visualized using single molecule fluorescence imaging by incorporating a fluorophore unit in the cyclic chains. The diffusive motion of the chains is quantitatively characterized by means of a combination of mean-squared displacement (MSD) analysis and a cumulative distribution function (CDF) analysis. The cyclic polymer exhibits multiple-mode diffusion which is distinct from its linear counterpart. The results demonstrate that the diffusional heterogeneity of polymers that is often hidden behind ensemble averaging can be revealed by the efficient synthesis of the cyclic polymers using the ESA-CF process and the quantitative analysis of the diffusive motion at the single molecule level using the MSD and CDF analyses.
  • ESA-CF Synthesis of Linear and Cyclic Polymers Having Densely Appended Perylene Units and Topology Effects on Their Thin-Film Electron Mobility
    Akihiro Kimura, Tsukasa Hasegawa, Takuya Yamamoto, Hidetoshi Matsumoto, Yasuyuki Tezuka
    MACROMOLECULES, 49, 16, 5831, 5840, AMER CHEMICAL SOC, Aug. 2016, [Peer-reviewed]
    English, Scientific journal, A pair of topologically contrastive, linear and cyclic polymers having densely appended perylene diimide (PDI) units have been prepared by means of an electrostatic self-assembly and covalent fixation (ESA-CF) process, using an assembly composed of either linear or cyclic polyacrylate anions of different segment lengths (DPn = 50, 93, and 128) accompanying countercations of a perylene diimide (PDI) derivative having a cyclic ammonium salt group (IIL/III and IIC/III, respectively). The subsequent heating treatment at 180 degrees C produced the covalently converted product, i.e., the linear IVL and the cyclic IVC, respectively, in which the PDI unit was introduced nearly quantitatively to the backbone acrylate units. The obtained linear and cyclic polymers having pendant PDI units were observed to form commonly spherical self-assemblies both in bulk and in solution states, while the solution viscosity was noticeably higher with the linear products than with the cyclic counterparts. The electron-only device (EOD) measurement by using thin-film samples of a series of cyclized products, IVC, revealed consistently higher electron carrier mobilities in comparison with the corresponding linear counterparts, IVL.
  • Construction of Hybrid-Multicyclic Polymer Topologies Composed of Dicyclic Structure Units by Means of An ESA-CF/Click-Linking Protocol
    Yoichiro Tomikawa, Takuya Yamamoto, Yasuyuki Tezuka
    MACROMOLECULES, 49, 11, 4076, 4087, AMER CHEMICAL SOC, Jun. 2016, [Peer-reviewed]
    English, Scientific journal, A series of tri- and tetracyclic polymer topologies, composed of an elementary dicyclic unit of either theta-, eight- or manacle-forms, have been constructed by means of an ESA-CF (electrostatic self-assembly and covalent fixation) protocol in conjunction with an alkyne-azide click linking technique. Thus, a theta-shaped poly(THF) precursor having an alkyne group at the junction position (Ic) has newly been prepared by an ESA-CF process using an assembly (1b/2d), composed of a star poly(THF) having N-phenylpyrrolidinium salt groups carrying a counteranion of a trifunctional carboxylate having an alkyne group. In addition, monocyclic polymer precursors having an azide group (Ha) as well as linear-cyclic (tadpole) (I1b) and linear-dicyclic (twin-head tadpole) (IIc) polymer precursors, both having an azide group at the tail-end position, have been prepared through the tandem click reaction of the respective monocyclic and dicyclic (eight-form) precursors having an alkyne group (Ia and Ib, respectively) with a linear asymmetric telechelic poly(THF) having an azide and an hydroxyl groups (1d), followed by the esterification with 4-azidobenzoic acid. A variety of hybrid-tricyclic polymer topologies (IIIa, Mb, and Inc) composed of a dicyclic (theta- or eight-shaped) and a monocyclic (simple ring or tadpole-shaped) units, and moreover, an unprecedented hybrid-tetracyclic topology composed of all three elementary dicyclic units of theta-, eight- and manacle-forms (IVb), in addition to a double-theta topology (IVa) have been constructed through the effective click-linking of complementarily reactive kyklo-telechelic precursors.
  • Hydrogel formation by the 'topological conversion' of cyclic PLA-PEO block copolymers
    Takuya Yamamoto, Kotaro Inoue, Yasuyuki Tezuka
    POLYMER JOURNAL, 48, 4, 391, 398, NATURE PUBLISHING GROUP, Apr. 2016, [Peer-reviewed]
    English, Scientific journal, An amphiphilic cyclic block copolymer consisting of poly(L- or D-lactide) and poly(ethylene oxide), that is, PLLA-PEO or PDLA-PEO, was synthesized from its corresponding linear triblock precursor, PLLA-PEO-PLLA or PDLA-PEO-PDLA, respectively, with alkenyl end groups. A mixture of the micellar dispersions of linear PLLA-PEO-PLLA and linear PDLA-PEO-PDLA formed a gel upon heating, whereas a mixture of the cyclic counterparts did not undergo this phase transition. These results suggest that the gelation behavior is directed by the topology of the polymer components. Furthermore, cyclic PLLA-PEO and cyclic PDLA-PEO block copolymers incorporating photocleavable o-nitrobenzyl units were synthesized. A mixture of the micellar dispersions of these block copolymers formed a gel upon ultraviolet irradiation via the 'topological conversion'.
  • Light- and Heat-Triggered Reversible Linear-Cyclic Topological Conversion of Telechelic Polymers with Anthryl End Groups
    Takuya Yamamoto, Sakyo Yagyu, Yasuyuki Tezuka
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 138, 11, 3904, 3911, AMER CHEMICAL SOC, Mar. 2016, [Peer-reviewed]
    English, Scientific journal, This study demonstrates the comprehensive investigation on the reversible linear cyclic topological conversion of hydrophilic and hydrophobic polymers with various molecular weights. The reactions were triggered by light or heat, which reversibly dimerize and cleave the anthryl or coumarinyl end groups of the telechelics. Poly(ethylene oxide) telechelics with anthryl end groups attached through electron-donating (Ant-O-PEO and Ant-CH2-PEO) and electron-withdrawing (Ant-CO2-PEO) linking groups were synthesized. While Ant-O-PEO and Ant-CH2-PEO decomposed upon photoirradiation at 365 nm, Ant-CO2-PEO efficiently cyclized through the photodimerization of the anthryl end groups both in water and in organic solvents shown by NMR, SEC, and MALDI-TOF MS. The lower the molecular weight, the faster the cyclization proceeded. When cyclized Ant-CO2-PEO was heated at 150 degrees C in bulk, the polymers quantitatively converted back into the original linear topology. Furthermore, repeatable linear cyclic topological conversion was confirmed. The reversible topological conversion of hydrophobic poly(tetrahydrofuran) telechelics with anthryl end groups (Ant-PTHF) was also successful. In addition, poly(ethylene oxide) telechelics with coumarinyl end groups (Cou-PEO) were also cyclized by irradiation at 365 nm in water. However, the cyclization hardly occurred when performed in methanol likely due to the lack of sufficient hydrophobic interaction of the coumarinyl end groups. Cyclized Cou-PEO was irradiated at 254 nm to test for linearization, finding the linear product and cyclic precursor were likely photoequilibrated.
  • Topological "Interfacial" Polymer Chemistry: Dependency of Polymer "Shape" on Surface Morphology and Stability of Layer Structures When Heating Organized Molecular Films of Cyclic and Linear Block Copolymers of n-Butyl Acrylate-Ethylene Oxide
    Qi Meng, Satoshi Honda, Yasuyuki Tezuka, Takuya Yamamoto, Atsuhiro Fujimori
    JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS, 54, 4, 486, 498, WILEY-BLACKWELL, Feb. 2016, [Peer-reviewed]
    English, Scientific journal, The "topological polymer chemistry" of amphiphilic linear and cyclic block copolymers at an air/water interface was investigated. A cyclic copolymer and two linear copolymers (AB-type diblock and ABA-type triblock copolymers) synthesized from the same monomers were used in this study. Relatively stable monolayers of these three copolymers were observed to form at an air/water interface. Similar condensed-phase temperature-dependent behaviors were observed in surface pressure-area isotherms for these three monolayers. Molecular orientations at the air/water interface for the two linear block copolymers were similar to that of the cyclic block copolymer. Atomic force microscopic observations of transferred films for the three polymer types revealed the formation of monolayers with very similar morphologies at the mesoscopic scale at room temperature and constant compression speed. ABA-type triblock linear copolymers adopted a fiber-like surface morphology via two-dimensional crystallization at low compression speeds. In contrast, the cyclic block copolymer formed a shapeless domain. Temperature-controlled out-of-plane X-ray diffraction (XRD) analysis of Langmuir-Blodgett (LB) films fabricated from both amphiphilic linear and cyclic block copolymers was performed to estimate the layer regularity at higher temperatures. Excellent heat-resistant properties of organized molecular films created from the cyclic copolymer were confirmed. Both copolymer types showed clear diffraction peaks at room temperature, indicating the formation of highly ordered layer structures. However, the layer structures of the linear copolymers gradually disordered when heated. Conversely, the regularity of cyclic copolymer LB multilayers did not change with heating up to 50 degrees C. Higher-order reflections (d(002), d(003)) in the XRD patterns were also unchanged, indicative of a highly ordered structure. (c) 2015 Wiley Periodicals, Inc.
  • Concise Click/ESA-CF Synthesis of Periodically-Positioned Trifunctional kyklo-Telechelic Poly(THF)s
    Haruna Wada, Takuya Yamamoto, Yasuyuki Tezuka
    MACROMOLECULES, 48, 17, 6077, 6086, AMER CHEMICAL SOC, Sep. 2015, [Peer-reviewed]
    English, Scientific journal, A concise two-step click/ESA-CF process has been developed to prepare a kyklo-telechelic poly(tetrahydrofuran), poly(THF), having three functional groups at the constant intervals. Thus, a key linear precursor (I), having N-phenylpyrrolidinium salt groups at the chain ends and having two hydroxyl groups at the prescribed inner positions, has been prepared through the alkyne-azide addition (click) reaction using one unit of a linear telechelic poly(THF) having a pair of an alkyne and a hydroxyl groups (1) and two units of a linear asymmetric telechelic poly(THF) having an azide and an N-phenylpyrrolidinium salt group (2). The subsequent polymer cyclization by means of an electrostatic self-assembly and covalent fixation (ESA-CF) process, by employing a dicarboxylate counteranion having an additional alkyne group (3) to I, could produce a trifunctional kyklo-telechelic poly(THF) (II), having two hydroxyl and one alkyne groups positioned at the constant intervals along the ring polymer backbone. The subsequent esterification of the hydroxyl groups in II was performed to give a kyklo-telechelic poly(THF) having three alkyne groups at the constant intervals (III), and a further click reaction of III with 2 was conducted to produce a ring polymer product having three emanating graft segments at the constant intervals along the ring unit (IV), i.e., a three-tail tadpole topology.
  • NMR Relaxometry for the Thermal Stability and Phase Transition Mechanism of Flower-like Micelles from Linear and Cyclic Amphiphilic Block Copolymers
    Haruna Wada, Yu Kitazawa, Shigeki Kuroki, Yasuyuki Tezuka, Takuya Yamamoto
    LANGMUIR, 31, 32, 8739, 8744, AMER CHEMICAL SOC, Aug. 2015, [Peer-reviewed]
    English, Scientific journal, Linear and cyclic amphiphilic block copolymers consisting of poly(ethylene oxide) (PEO) as the hydrophilic segment and poly(methyl acrylate) or poly(ethyl acrylate) as the hydrophobic segments were synthesized and self-assembled to form flower-like micelles. The micelles from linear (methyl acrylate)(12)(ethylene oxide)(73)(methyl acrylate)(12) (M-n = 1000-3200-1000, l-MOM) showed a cloud point (T-c) at 46 degrees C by the transmittance of the micellar solution, whereas that of cyclic (methyl acrylate)(30)(ethylene oxide)(79) (M-n = 2600-3500, c-MO) increased to 72 degrees C, as previously reported. DLS showed comparable diameters (l-MOM, 14 nm; c-MO, 12 nm) and T-c values (/-MOM, 48 degrees C; c-MO, 75 degrees C). For the investigation of the difference in T-c and the phase transition mechanism based on the polymer topology, NMR relaxometry was performed to determine the spin lattice (T-1) and spin spin (T-2) relaxation times. A decrease in T-2 of the PEO segment in both l-MOM and c-MO was observed above T, suggesting that slow large-scale motions, such as the detachment of a chain end from the core, bridging, and interpenetration of the micelles, were inhibited. T-1 of the PEO segment in l-MOM continuously increased in the experimental temperature range, indicating that the segment is hydrated even above its T-c. On the other hand, that of c-MO reached a ceiling above its T-c, likely due to the prevention of the rotation of the PEO main chain bonds caused by dehydration. Similar results were obtained for linear (ethyl acrylate)(8)(ethylene oxide)(79)(ethyl acrylate)(8) (M-n = 800-3500-800, l-EOE) and its cyclic (ethyl acrylate)(15)(ethylene oxide)(78) (M-n = 1500-3400, c-EO).
  • Folding Construction of a Pentacyclic Quadruply fused Polymer Topology with Tailored kyklo-Telechelic Precursors
    Hiroyuki Heguri, Takuya Yamamoto, Yasuyuki Tezuka
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 54, 30, 8688, 8692, WILEY-V C H VERLAG GMBH, Jul. 2015, [Peer-reviewed]
    English, Scientific journal, A pentacyclic quadruply fused polymer topology has been constructed for the first time through alkyne-azide addition (click) and olefin metathesis (clip) reactions in conjunction with an electrostatic self-assembly and covalent fixation (ESA-CF) process. Thus, a spiro-type, tandem tetracyclic poly(tetrahydrofuran), poly(THF), precursor having two allyloxy groups at the opposite positions of the four ring units was prepared by the click-linking of one unit of an eight-shaped precursor having alkyne groups at the opposite positions with two units of a single-cyclic counterpart having an azide and an alkene group at the opposite positions. Both are obtainable through ESA-CF. The subsequent metathesis clip-folding of the tetracyclic precursor could afford a pentacyclic quadruply fused polymer product, of shippo form, in 19% yield.
  • A study on emulsion stabilization induced with linear and cyclized polystyrene-poly(ethylene oxide) block copolymer surfactants
    Eisuke Baba, Toshiaki Yatsunami, Takuya Yamamoto, Yasuyuki Tezuka
    POLYMER JOURNAL, 47, 5, 408, 412, NATURE PUBLISHING GROUP, May 2015, [Peer-reviewed]
    English, Scientific journal
  • Cyclic polymers revealing topology effects upon self-assemblies, dynamics and responses
    Takuya Yamamoto, Yasuyuki Tezuka
    SOFT MATTER, 11, 38, 7458, 7468, ROYAL SOC CHEMISTRY, 2015, [Peer-reviewed]
    English, A variety of single-and multicyclic polymers having programmed chemical structures with guaranteed purity have now become obtainable owing to a number of synthetic breakthroughs achieved in recent years. Accordingly, a broadening range of studies has been undertaken to gain updated insights on fundamental polymer properties of cyclic polymers in either solution or bulk, in either static or dynamic states, and in self-assemblies, leading to unusual properties and functions of polymer materials based on their cyclic topologies. In this article, we review recent studies aiming to achieve distinctive properties and functions by cyclic polymers unattainable by their linear or branched counterparts. We focus, in particular, on selected examples of unprecedented topology effects of cyclic polymers upon self-assemblies, dynamics and responses, to highlight current progress in Topological Polymer Chemistry.
  • Photoinduced topological transformation of cyclized polylactides for switching the properties of homocrystals and stereocomplexes
    Naoto Sugai, Shigeo Asai, Yasuyuki Tezuka, Takuya Yamamoto
    POLYMER CHEMISTRY, 6, 19, 3591, 3600, ROYAL SOC CHEMISTRY, 2015, [Peer-reviewed]
    English, Scientific journal, Cyclized poly(L-lactide) and poly(D-lactide) (M-n similar to 3 kDa) incorporating an o-nitrobenzyl group as a photocleavable linker were synthesized and photoirradiated for topological transformation to form photocleaved linear polylactides. By DSC, T-m of the cyclized stereocomplex (167 degrees C) decreased by more than 40 degrees C from that of the linear prepolymers (209 degrees C) despite their essentially identical molecular weights. Upon the photocleavage, the resulting linear stereocomplex showed almost the same Tm (211 degrees C) as that before the cyclization. The enthalpy of melting of crystals having an infinite thickness, i.e. Delta H-m(100%), and the surface free energy (sigma(e)) were determined by the combination of WAXD, SAXS, and DSC. Both Delta H-m(100%) and sigma(e) were considerably smaller for the cyclized polylactide homocrystals and stereocomplexes than those of the linear prepolymers and photocleaved products. These suggest that the absolute enthalpy of the melt state is lower, and the crystalline-amorphous interface is more stable for the cyclized polylactides arising from the topology.
  • Single-molecule imaging reveals topological isomer-dependent diffusion by 4-armed star and dicyclic 8-shaped polymers
    Satoshi Habuchi, Susumu Fujiwara, Takuya Yamamoto, Yasuyuki Tezuka
    POLYMER CHEMISTRY, 6, 22, 4109, 4115, ROYAL SOC CHEMISTRY, 2015, [Peer-reviewed]
    English, Scientific journal, Diffusion dynamics of topological isomers of polymer molecules was investigated at the single-molecular level in the melt state by employing the fluorophore-incorporated 4-armed star and the corresponding doubly-cyclized, 8-shaped poly(THF) chains. While the single-molecule fluorescence imaging experiment revealed that the diffusion of the 4-armed star polymer was described by a single Gaussian distribution, the diffusion of the 8-shaped polymer exhibited a double Gaussian distribution behaviour. We reasoned that the two 8-shaped polymeric isomers have distinct diffusion modes in the melt state, although ensemble-averaged experimental methods cannot detect differences in the overall conformational state of the isomers. The single-molecule experiments suggested that one of the 8-shaped polymeric isomers, having the horizontally oriented form, causes an efficient threading with the linear matrix chains which leads to slower diffusion compared with the corresponding 4-armed star polymer, while the other 8-shaped polymeric isomer, having the vertically oriented form, displayed faster diffusion by the suppression of effective threading with the linear matrix chains due to its contracted chain conformation.
  • Phase separation and self-assembly of cyclic amphiphilic block copolymers with a main-chain liquid crystalline segment
    Satoshi Honda, Maito Koga, Masatoshi Tokita, Takuya Yamamoto, Yasuyuki Tezuka
    POLYMER CHEMISTRY, 6, 22, 4167, 4176, ROYAL SOC CHEMISTRY, 2015, [Peer-reviewed]
    English, Scientific journal, A series of linear and cyclized amphiphilic block copolymers consisting of poly(acrylic acid) (AA(m)) and main-chain liquid crystalline (LC) poly(3-methylpentamethylene-4,4'-bibenzoate) (BBn) segments were newly synthesized. Solid state morphology was investigated by X-ray scattering. Linear AA(21)BB(9)AA(21), cyclic AA(33)BB(10), and cyclic AA(51)BB(18) formed lamellar microdomains, where the BBn segment of cyclic AA51BB18 formed a smectic CA phase. On the other hand, cylinder-type microdomains were formed by linear AA(44)BB(9)AA(44) and cyclic AA(100)BB(9). These amphiphilic block copolymers were self-assembled in water to form vesicles or cylindrical micelles, depending on the polymer concentration of the initial THF solution. The response of these nanostructures against an electric field demonstrated that the vesicles formed from linear AA(25)BB(14)AA(25) and cyclic AA(51)BB(18) turned into substantially larger aggregates, likely due to the reorganization of the LC segment in the bilayer.
  • Molecular Design of Discrete Oligosaccharide-block-Oligodimethylsiloxane System: Toward Microphase Separation with 1 nm Domain Size and Angstrom-Scale Size Control"               
    Nishimura, Taiki, Lee, Chaehun, Nunokawa, Ryosuke, Cheng, Yu-Hung, Li, Feng, Yamamoto, Takuya, Tajima, Kenji, Borsali, Redouane, Chen, Hsin-Lung, Satoh, Toshifumi, Isono, Takuya
    Macromolecules, Dec. 2014, [Peer-reviewed]
  • 環状両親媒性ブロック共重合体が形成するミセルの構造と機能
    Yamamoto Takuya
    C & I Commun., 39, 4, 12, 14, 日本化学会コロイドおよび界面化学部会, Dec. 2014, [Peer-reviewed], [Invited]
    Japanese
  • Construction of Double-Eight and Double-Trefoil Polymer Topologies with Core-Clickable kyklo-Telechelic Precursors
    Yoichiro Tomikawa, Hiroto Fukata, Yee Song Ko, Takuya Yamamoto, Yasuyuki Tezuka
    MACROMOLECULES, 47, 23, 8214, 8223, AMER CHEMICAL SOC, Dec. 2014, [Peer-reviewed]
    English, Scientific journal, A dicyclic, eight-shaped and a tricyclic, trefoil-shaped poly(THF) both having an alkyne group at the core position (II and III, respectively) have been introduced as versatile core-clickable kyklo-telechelic precursors. The prepolymer II has been prepared by an ESA-CF (electrostatic self-assembly and covalent fixation) process using an assembly (1a/2b), composed of two units of linear poly(THF) having N-phenylpyrrolidinium salt groups carrying one unit of a tetrafunctional carboxylate having an alkyne group as a counteranion. Alternatively, the prepolymer III has been produced through a click process using a cyclic poly(THF) precursor having an azide group (Ia), obtainable also by the ESA-CF technique, with a tripropargylated pentaerythritol derivative (2c) followed by the esterification with 4-pentynoic acid to introduce again an alkyne group. The subsequent click coupling reaction of II and III with a linear telechelic poly(THF) having azide groups (1b) afforded successfully novel tetra- and hexacyclic bridged-spiro hybrid polymer topologies, i.e., double-eight and double-trefoil constructions.
  • Dependency of the Molecular "Shape" on Surface Morphology of Organized Molecular Films of Cyclic and Linear Block Copolymer of Polyethylene Oxide–Butyl Acrylate
    Masamichi Hashimoto, Qi Meng, Satoshi Honda, Yasuyuki Tezuka, Takuya Yamamoto, Atsuhiro Fujimori
    Trans. Mat. Res. Soc. Jpn., 39, 1, 83, 86, The Materials Research Society of Japan, Aug. 2014, [Peer-reviewed]
    English, Scientific journal, A "topological polymer chemistry" at air/water interface is investigated by using an amphiphilic linear and cyclic block copolymers. A cyclic copolymer and two kind of linear polymers (AB-type diblock and ABA-type triblock copolymers) with same components were used in the study. The relatively stable monolayers of these three kinds of copolymers were formed at the air/water interface. The analogous condensed tendency and temperature dependency were observed in surface pressure-area isotherms of three kinds of monolayers. It is considered that molecular orientation at air/water interface of two kinds of liner block copolymers is similar to that of cyclic block copolymer. From the result of atomic force microscopic observation of transfered films, monolayers of the three kinds of polymers have formed a very similar morphology at mesoscopic scale under the conditions at room temperature and the constant compression speed. It finds that ABA type triblock liner copolymer formed fiber-like surface morphology by the two-dimensional crystallization based on the low compression speed. On the other hand, cyclic block copolymer formed shapeless domain.
  • Molecular Arrangement of Organized Molecular Films of Linear and Cyclic Amphiphilic Block Copolymers with Different Shapes
    Qi Meng, Masamichi Hashimoto, Satoshi Honda, Yasuyuki Tezuka, Takuya Yamamoto, Atsuhiro Fujimori
    Trans. Mat. Res. Soc. Jpn., 39, 1, 78, 82, The Materials Research Society of Japan, Aug. 2014, [Peer-reviewed]
    English, Scientific journal, A "topological polymer chemistry" as a new concept in polymer science at the air/water interface is investigated by using amphiphilic linear and cyclic block copolymers consisting of butyl acrylate and ethylene oxide. The relatively stable monolayers of these two kinds of amphiphilic copolymers were formed at the air/water interface. In addition, these two kinds of amphiphilic copolymers constructed highly ordered Langmuir-Blodgett (LB) multilayers. In order to estimate the layered regularity under high temperature, the temperature-controlled out-of-plane X-ray diffraction (XRD) of LB films of amphiphilic linear and cyclic block copolymers was obtained. As a result, excellent heat-resistant propertyies of organized molecular films of the cyclic copolymer were confirmed. At room temperature, both copolymers showed clear diffraction peaks based on the formation of highly ordered layer structures. However, in the case of linear copolymers, layered structures were gradually disordered with heating. On the other hand, regularity of LB multilayers of the cyclic copolymers did not change with heating up to 50 °C. In this case, higher order reflections (d002, d003) of XRD are also unchanged, which means the formation of highly ordered regularity.
  • Synthesis of core-fluorescent four-armed star and dicyclic 8-shaped poly(THF)s by electrostatic self-assembly and covalent fixation (ESA-CF) protocol
    Susumu Fujiwara, Takuya Yamamoto, Yasuyuki Tezuka, Satoshi Habuchi
    REACTIVE & FUNCTIONAL POLYMERS, 80, 3, 8, ELSEVIER SCIENCE BV, Jul. 2014, [Peer-reviewed]
    English, Scientific journal, A pair of four-armed star and dicyclic 8-shaped poly(tetrahydrofuran)s, poly(THF)s, possessing a perylene diimide group at the core position (Ia and Ib, respectively) were synthesized by means of an electrostatic self-assembly and covalent fixation (ESA-CF) protocol. Mono- and bifunctional poly(THF)s having N-phenylpiperidinium salt end groups accompanying a perylene diimide tetracarboxylate as a counteranion were prepared by the ion-exchange reaction, and the subsequent covalent conversion by reflux in toluene afforded the corresponding core-fluorescent four-armed star and dicyclic 8-shaped poly(THF)s, (Ia and Ib, respectively) for the use of single-molecule fluorescence microscopy measurements. (C) 2013 Elsevier Ltd. All rights reserved.
  • Constructing a Macromolecular K-3,K-3 Graph through Electrostatic Self-Assembly and Covalent Fixation with a Dendritic Polymer Precursor
    Takuya Suzuki, Takuya Yamamoto, Yasuyuki Tezuka
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 136, 28, 10148, 10155, AMER CHEMICAL SOC, Jul. 2014, [Peer-reviewed]
    English, Scientific journal, A triply fused tetracyclic macromolecular K-3,K-3 graph has been constructed through electrostatic self-assembly of a uniformly sized dendritic polymer precursor having six cylic ammonium salt end groups carrying two units of a trifunctional carboxylate counteranions, and subsequent covalent conversion by the ring-opening reaction of cyclic ammonium salt groups at an elevated temperature under dilution. The K-3,K-3 graph product was isolated from the two constitutional isomers by means of a recycling SEC technique, as the hydrodynamic volume of the triply fused tetracyclic K-3,K-3 product is remarkably contracted in comparison with another isomer having a ladder form in solution.
  • Structural Characteristics of Amphiphilic Cyclic and Linear Block Copolymer Micelles in Aqueous Solutions
    Kyuyoung Heo, Young Yong Kim, Yu Kitazawa, Mihee Kim, Kyeong Sik Jin, Takuya Yamamoto, Moonhor Ree
    ACS MACRO LETTERS, 3, 3, 233, 239, AMER CHEMICAL SOC, Mar. 2014, [Peer-reviewed]
    English, Scientific journal, The structural characteristics of aqueous micelles composed of amphiphilic cyclic poly(n-butyl acrylate-b-ethylene oxide) (cyclic PBA-b-PEO) or a linear analogue (i.e., linear poly(n-butyl acrylate-b-ethylene oxide-b-n-butyl acrylate) (linear PBA-b-PEO-b-PBA)) were examined for the first time using synchrotron X-ray scattering techniques and quantitative data analysis. The scattering data were analyzed using a variety of methodologies in a comprehensive complementary manner. These analyses provided details of the structural information about the micelles. Both micelles were found to consist of a core and a fuzzy shell; however, the cyclic block copolymer had a strong tendency to form micelles with core and shell parts that were more compact and dense than the corresponding parts of the linear block copolymer micelles. The PBA block of the cyclic copolymer was found to form a hydrophobic core with a density that exceeded the density of the homopolymer in the bulk state. The structural differences originated primarily from the topological difference between the cyclic and linear block copolymers. The elimination of the chain end groups (which introduced entropy and increased the excess excluded volume) from the amphiphilic block copolymer yielded more stable dense micelles in solution.
  • Click Construction of Spiro-and Bridged-Quatrefoil Polymer Topologies with Kyklo-Telechelics Having an Azide Group
    Yee Song Ko, Takuya Yamamoto, Yasuyuki Tezuka
    MACROMOLECULAR RAPID COMMUNICATIONS, 35, 4, 412, 416, WILEY-V C H VERLAG GMBH, Feb. 2014, [Peer-reviewed]
    English, Scientific journal, Unprecedented tetracyclic polymer topologies with spiro- and a bridged-type quatrefoil forms are effectively constructed through an alkyne-azide, click-linking reaction by employing a kyklo-telechelic poly(tetrahydrofuran), poly(THF), precursor having an azide group, obtained through an electrostatic self-assembly and covalent fixation (ESA-CF) process, and complementary tetrafunctional alkyne reagents of either a pentaerythritol derivative or a four-armed star telechelic polymer precursor.
  • S(N)2 regioselectivity in the esterification of 5-and 7-membered azacycloalkane quaternary salts: a DFT study to reveal the transition state ring conformation prevailing over the ground state ring strain
    Akihiro Kimura, Susumu Kawauchi, Takuya Yamamoto, Yasuyuki Tezuka
    ORGANIC & BIOMOLECULAR CHEMISTRY, 12, 34, 6717, 6724, ROYAL SOC CHEMISTRY, 2014, [Peer-reviewed]
    English, Scientific journal, The nucleophilic esterification of 5- and 7-membered N-phenylcyclic ammonium salts resulted in distinctive regioselectivity, despite their comparable ring strain in the ground states relative to the corresponding cyclopentane and cycloheptane (both 25.9 kJ mol(-1)). The former underwent a selective ring-opening reaction, while the latter predominantly underwent ring-emitting with concurrent ring-opening reactions. A DFT study of the model compounds revealed that the regioselection in the 5- and 7-membered azacycloalkane quaternary salts is plausibly directed by the transition state ring conformation, and not by the ground state ring strain. Remarkably, at the ring-opening transition state, the 5-membered cyclic skeletal structure expands toward the unstrained and thus less frustrated 6-membered cyclohexane conformation. On the other hand, the 7-membered counterpart expands at the ring-opening transition state toward the more frustrated 8-membered cyclooctane conformation to promote the alternative ring-emitting process.
  • Folding Construction of Doubly Fused Tricyclic, beta- and gamma-Graph Polymer Topologies with kyklo-Telechelic Precursors Obtained through an Orthogonal Click/ESA-CF Protocol
    Masahito Igari, Hiroyuki Heguri, Takuya Yamamoto, Yasuyuki Tezuka
    MACROMOLECULES, 46, 18, 7303, 7315, AMER CHEMICAL SOC, Sep. 2013, [Peer-reviewed]
    English, Scientific journal, An alkyne-azide addition (click) reaction of a linear poly(tetrahydrofuran), poly(THF), precursor having an alkyne group at the center position and cyclic ammonium salt end groups has been applied with the complementary linear poly(THF) precursors having an azide group at single or both chain ends to produce asymmetric star- and H-shaped poly(THF) precursors having cyclic ammonium salt end groups. The subsequent electrostatic self-assembly and covalent fixation (ESA-CF) process after introducing dicarboxylate counteranions having an additional alkene or alkyne group could afford the designated kyklo-telechelic precursors, having either a tadpole form containing an alkyne group at the top-head and an alkene group at the tail-end positions or an isomeric manacle/theta form containing two alkene groups at the orthogonal positions. The further click coupling of the former with a linear telechelic precursor having azide groups followed by the metathesis folding (clip) process could produce effectively a doubly fused tricyclic polymer having beta-graph topology. Moreover, the convergent folding by the clip reaction of the latter manacle/theta isomeric precursors could produce exclusively another doubly fused tricyclic polymer having gamma-graph topology.
  • Single-Molecule Study on Polymer Diffusion in a Melt State: Effect of Chain Topology
    Satoshi Habuchi, Susumu Fujiwara, Takuya Yamamoto, Martin Vacha, Yasuyuki Tezuka
    ANALYTICAL CHEMISTRY, 85, 15, 7369, 7376, AMER CHEMICAL SOC, Aug. 2013, [Peer-reviewed]
    English, Scientific journal, We report a new methodology for studying diffusion of individual polymer chains in a melt state, with special emphasis on the effect of chain topology. A perylene diimide fluorophore was incorporated into the linear and cyclic poly(THF)s, and real-time diffusion behavior of individual chains in a melt of linear poly(THF) was measured by means of a single-molecule fluorescence imaging technique. The combination of mean squared displacement (MSD) and cumulative distribution function (CDF) analysis demonstrated the broad distribution of diffusion coefficient of both the linear and cyclic polymer chains in the melt state. This indicates the presence of spatiotemporal heterogeneity of the polymer diffusion which occurs at much larger time and length scales than those expected from the current polymer physics theory. We further demonstrated that the cyclic chains showed marginally slower diffusion in comparison with the linear counterparts, to suggest the effective suppression of the translocation through the threading-entanglement with the linear matrix chains. This coincides with the higher activation energy for the diffusion of the cyclic chains than of the linear chains. These results suggest that the single-molecule imaging technique provides a powerful tool to analyze complicated polymer dynamics and contributes to the molecular level understanding of the chain interaction.
  • Synthesis of cyclic polymers and topology effects on their diffusion and thermal properties
    Takuya Yamamoto
    POLYMER JOURNAL, 45, 7, 711, 717, NATURE PUBLISHING GROUP, Jul. 2013, [Peer-reviewed]
    English, In comparison with their linear counterparts, cyclic polymers exhibit distinctive properties due to their topology. The synthesis of cyclic polymers and the functionalities arising from their unique shapes, namely topology effects, are reviewed. The electrostatic self-assembly and covalent fixation (ESA-CF) process was used in conjunction with click chemistry and with olefin metathesis to construct selectively a variety of unprecedented polymer architectures, such as manacle-shaped and tandem multicycles, as well as doubly fused tricyclic and triply fused tetracyclic topologies. Moreover, the self-assembly of a cyclic amphiphilic block copolymer, which was prepared by intramolecular metathesis, produced micelles that exhibited an increase in thermal stability of approximately 50 degrees C compared with the micelles formed from the linear prepolymer. Single-molecule spectroscopic studies also revealed different diffusion modes for cyclic and linear polymers.
  • Systematic Synthesis of Block Copolymers Consisting of Topological Amphiphilic Segment Pairs from kyklo- and kentro-Telechelic PEO and Poly(THF)
    Fumiya Hatakeyama, Takuya Yamamoto, Yasuyuki Tezuka
    ACS MACRO LETTERS, 2, 5, 427, 431, AMER CHEMICAL SOC, May 2013, [Peer-reviewed]
    English, Scientific journal, A set of four types of block copolymers consisting of topological amphiphilic segment pairs was effectively synthesized via kyklo- (functionalized cyclic) and kentro- (center-functionalized linear) telechelic poly(ethylene oxide) (PEO) and poly(tetrahydrofuran) (poly(THF)). Accordingly, kyklo- and kentro-telechelic PEO with an ethynyl group was newly prepared from relevant linear PEO precursors with quinuclidinium end groups and an ethynyl-functionalized dicarboxylate counteranion by the electrostatic self-assembly and covalent fixation (ESA-CF) process. Similarly, kyklo- and kentro-telechelic poly(THF) with an azido group was obtained. The PEO and poly(THF) telechelics were subjected to click chemistry to systematically produce amphiphilic block copolymers with two symmetric topological forms, that is, an "8" shape (I-C center dot IIC) and a four-armed star shape (I-L center dot IIL), and two asymmetric topological forms, that is, twin-tailed tadpole shapes (I-L center dot IIC and I-C center dot IIL) with respect to the hydrophilic-hydrophobic plane.
  • Synthesis of cyclic ammonium end groups for a selective ring-emitting reaction: Elucidation of the reaction mechanism by DFT studies
    Kimura Akihiro, Yamamoto Takuya, Tezuka Yasuyuki, Kawauchi Susumu
    ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, 245, 07 Apr. 2013, [Peer-reviewed]
  • Regioselective Ring-Emitting Esterification on Azacyclohexane Quaternary Salts: A DFT and Synthetic Study for Covalent Fixation of Electrostatic Polymer Self-Assemblies
    Akihiro Kimura, Shinnosuke Takahashi, Susumu Kawauchi, Takuya Yamamoto, Yasuyuki Tezuka
    JOURNAL OF ORGANIC CHEMISTRY, 78, 7, 3086, 3094, AMER CHEMICAL SOC, Apr. 2013, [Peer-reviewed]
    English, Scientific journal, A regioselective nucleophilic esterification upon six-membered, thus considered unstrained, azacyclohexane quaternary salts has been disclosed by DFT calculations using a model compound and subsequent experimental studies of nucleophilic substitution on N-phenyl-3,3-dimethylpiperidinium salt groups at the polymer chain ends by carboxylate anions. Art exclusive ring-emitting esterification was proposed theoretically and confirmed experimentally to produce a simple ester group, in contrast to less robust amino-ester linkages through an alternative ring-opening process with strained five-membered ammonium salts. This reaction was subsequently applied to a prototypical process of an electrostatic self-assembly and covalent fixation (ESA-CF) technique to produce a ring polymer having simple ester linking units.
  • Topology dependent diffusion in polymer melts revealed by a single-molecule study
    Habuchi Satoshi, Fujiwara Susumu, Yamamoto Takuya, Vacha Martin, Tezuka Yasuyuki
    Abstracts of Papers of the American Chemical Society, 245, 2013, [Peer-reviewed]
  • 環状の高分子が発現する興味深い機能
    Yamamoto Takuya
    表面, 51, 6, 297, 306, 広信社, 2013, [Invited]
    Japanese, Scientific journal
  • Straightforward synthesis of functionalized cyclic polymers in high yield via RAFT and thiolactone-disulfide chemistry
    Milan M. Stamenovic, Pieter Espeel, Eisuke Baba, Takuya Yamamoto, Yasuyuki Tezuka, Filip E. Du Prez
    POLYMER CHEMISTRY, 4, 1, 184, 193, ROYAL SOC CHEMISTRY, 2013, [Peer-reviewed]
    English, Scientific journal, An efficient synthetic pathway toward cyclic polymers based on the combination of thiolactone and disulfide chemistry has been developed. First, heterotelechelic linear polystyrene (PS) containing an alpha-thiolactone (TLa) and an omega-dithiobenzoate group was synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization, employing a newly designed TLa-bearing chain transfer agent (CTA). The subsequent reaction of this heterotelechelic polymer with an amine, which acts as a nucleophile for both the TLa and dithiobenzoate units, generated the alpha,omega-thiol-telechelic PS under ambient conditions without the need for any catalyst or other additives. The arrangement of thiols under a high dilution afforded single cyclic PS (c-PS) through an oxidative disulfide linkage. The cyclic PS (c-PS) disulfide ring formation was evidenced by SEC, MALDI-TOF MS and H-1-NMR characterization. Moreover, we demonstrated a controlled ring opening via either disulfide reduction or thiol-disulfide exchange to enable easy and clean topology transformation. Furthermore, to illustrate the broad utility of this synthetic methodology, different amines including functional ones were employed, allowing for the one-step preparation of functionalized cyclic polymers with high yields.
  • Tuneable enhancement of the salt and thermal stability of polymeric micelles by cyclized amphiphiles
    Satoshi Honda, Takuya Yamamoto, Yasuyuki Tezuka
    Nature Communications, 4, 2013, [Peer-reviewed]
    English, Scientific journal, Cyclic molecules provide better stability for their aggregates. Typically in nature, the unique cyclic cell membrane lipids allow thermophilic archaea to inhabit extreme conditions. By mimicking the biological design, the robustness of self-assembled synthetic nanostructures is expected to be improved. Here we report topology effects by cyclized polymeric amphiphiles against their linear counterparts, demonstrating a drastic enhancement in the thermal, as well as salt stability of self-assembled micelles. Furthermore, through coassembly of the linear and cyclic amphiphiles, the stability was successfully tuned for a wide range of temperatures and salt concentrations. The enhanced thermal/salt stability was exploited in a halogen exchange reaction to stimulate the catalytic activity. The mechanism for the enhancement was also investigated. These topology effects by the cyclic amphiphiles offer unprecedented opportunities in polymer materials design unattainable by traditional means. © 2013 Macmillan Publishers Limited. All rights reserved.
  • Effective Synthesis and Crystal Structure of a 24-Membered Cyclic Decanedisulfide Dimer
    Yukihiro Tada, Takuya Yamamoto, Yasuyuki Tezuka, Tadashi Kawamoto, Takehiko Mori
    CHEMISTRY LETTERS, 41, 12, 1678, 1680, CHEMICAL SOC JAPAN, Dec. 2012, [Peer-reviewed]
    English, Scientific journal, A 24-membered cyclic decaneclisulfide dimer (1,2,13,14-tetrathiacyclotetracosane) was effectively synthesized by resin-supported cyclization of 1,10-decanedithiol. Despite the formation of a series of cyclic oligomers, no monomeric decanedisulfide resulted. The crystal structure of the dimeric macrocycle was reported.
  • Synthesis of Orientationally Isomeric Cyclic Stereoblock Polylactides with Head-to-Head and Head-to-Tail Linkages of the Enantiomeric Segments
    Naoto Sugai, Takuya Yamamoto, Yasuyuki Tezuka
    ACS MACRO LETTERS, 1, 7, 902, 906, AMER CHEMICAL SOC, Jul. 2012, [Peer-reviewed]
    English, Scientific journal, A pair of orientationally isomeric cyclic stereoblock polylactides (PLAs) possessing head-to-head (HH) and head-to-tail (HT) linkages between the poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA) segments was synthesized through click chemistry and ring-closing metathesis (RCM) of three asymmetrically functionalized telechelic precursors. Thus, alpha-ethenyl-omega-azido-PLLA (2a) was reacted with alpha-ethenyl-omega-ethynyl-PDLA (2b) and alpha-ethynyl-omega-ethenyl-PDLA (2c) via click chemistry to form ethenyl telechelic stereoblock PLAs with HH and HT orientations (3a and 3b), respectively. The subsequent RCM produced cyclic stereoblock PLAs with the corresponding linking manners (4a and 4b). The effect of the topology on the melting temperature of the series of isomeric linear and cyclic PLAs having the contrastive linking orientations was systematically investigated.
  • Self-assembly and functions of cyclic polymers
    Eisuke Baba, Takuya Yamamoto
    Topological Polymer Chemistry: Progress of Cyclic Polymers in Syntheses, Properties, and Functions, 329, 348, World Scientific Publishing Co., 01 Jan. 2012, [Peer-reviewed]
    English, In book, This chapter focuses on recent studies on the self-assembly of cyclic block copolymers and their functions. The properties of cyclic polymers have been known to differ from corresponding linear counterparts caused by topology effects. On the basis of topology effects, the morphology and properties of self-assemblies can be controlled. Applications including drug delivery system are the subjects of intensive researches by taking advantage of the unique properties of cyclic polymers.
  • ATRP-RCM polymer cyclization: synthesis of amphiphilic cyclic polystyrene-b-poly(ethylene oxide) copolymers
    Eisuke Baba, Satoshi Honda, Takuya Yamamoto, Yasuyuki Tezuka
    POLYMER CHEMISTRY, 3, 7, 1903, 1909, ROYAL SOC CHEMISTRY, 2012, [Peer-reviewed]
    English, Scientific journal, A novel amphiphilic block copolymer, i.e., cyclic polystyrene-b-poly(ethylene oxide) (cyclic PS-b-PEO 2), was synthesized through atom-transfer radical polymerization (ATRP), followed by ring-closing metathesis (RCM). Thus, a bromobenzyl-terminated PS-b-PEO-b-PS (6) was first prepared by ATRP of styrene using a PEO macroinitiator having 2-bromoisobutyryl groups (5). The subsequent end-group conversion into allyl groups was performed quantitatively with allyltrimethylsilane (ATMS) in the presence of TiCl4. The allyl-telechelic triblock copolymer PS-b-PEO-b-PS (7) thus obtained was subjected to metathesis polymer cyclization with a Grubbs' 2nd generation catalyst to produce amphiphilic cyclic PS-b-PEO (2).
  • A Programmed Polymer Folding: Click and Clip Construction of Doubly Fused Tricyclic and Triply Fused Tetracyclic Polymer Topologies
    Naoto Sugai, Hiroyuki Heguri, Takuya Yamamoto, Yasuyuki Tezuka
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 133, 49, 19694, 19697, AMER CHEMICAL SOC, Dec. 2011, [Peer-reviewed]
    English, Scientific journal, A tandem alkyne-azide addition, i.e., click, and an olefin metathesis condensation, i.e., clip, reactions in conjunction with an electrostatic self-assembly and covalent fixation (ESA-CF) process, have been demonstrated as effective means to produce constructions of programmed folding of polymers having doubly fused tricyclic and triply fused tetracyclic topologies. Thus, a series of cyclic poly(tetrahydrofuran), poly(THF), precursors having an allyloxy group and an alkyne group (Ia), an allyloxy group and an azide group (Ib), and two alkyne groups (Ic) at the opposite positions was prepared by means of the ESA-CF method. The subsequent click reactions of Ia with a linear telechelic poly(THF) precursor having azide end groups (Id) and of Ib with Ic afforded a bridged dicyclic polymer (IIa) and a tandem Spiro tricyclic precursor (IIb), respectively, both having two allyloxy groups at the opposite positions of the ring units. Finally, the intramolecular metathesis condensation reaction of IIa and of IIb in the presence of a Grubbs catalyst was performed to construct effectively a doubly fused tricyclic and a triply fused tetracyclic polymer topologies (III and IV), respectively.
  • Cyclic and Multicyclic Topological Polymers
    Takuya Yamamoto, Yasuyuki Tezuka
    Complex Macromolecular Architectures: Synthesis, Characterization, and Self-Assembly, 1, 19, John Wiley and Sons, 03 May 2011, [Peer-reviewed]
    English, In book, Recent developments in topological polymer chemistry have been outlined. First, the remarkable progress observed in the synthesis of ring polymers, either by a ring-expansion polymerization process or by a polymer cyclization process with telechelic precursors, has been reviewed. Secondly, notable examples of functional ring polymers obtainable, in particular, by means of an electrostatic self-assembly and covalent fixation strategy, have been described. Those include (1) a ring polymer having an H-bonding unit for the effective synthesis of polymer catenanes, (2) a ring polymer having a chromophore unit to reveal topology effects in polymer diffusion by single-molecule spectroscopy, and (3) a defect-free ring polymer to disclose topology effects in crystallization dynamics. Finally, new synthetic approaches for topological polymers having multicyclic, i.e. fused, spiro and bridged, constructions have been discussed. © 2011 John Wiley &
    Sons (Asia) Pte Ltd.
  • Topological polymer chemistry by programmed self-assembly and effective linking chemistry
    Takuya Yamamoto, Yasuyuki Tezuka
    EUROPEAN POLYMER JOURNAL, 47, 4, 535, 541, PERGAMON-ELSEVIER SCIENCE LTD, Apr. 2011, [Peer-reviewed]
    English, Scientific journal, Ongoing challenges in topological polymer chemistry are reviewed. In particular, we focus on recent developments in an "electrostatic self-assembly and covalent fixation (ESA-CF)" process in conjunction with effective linking/cleaving chemistry including a metathesis process and an alkyne-azide click reaction. A variety of novel cyclic polymers having specific functional groups and unprecedented multicyclic macromolecular topologies have been realized by combining intriguing synthetic protocols. (C) 2010 Elsevier Ltd. All rights reserved.
  • Topological polymer chemistry: a cyclic approach toward novel polymer properties and functions
    Takuya Yamamoto, Yasuyuki Tezuka
    POLYMER CHEMISTRY, 2, 9, 1930, 1941, ROYAL SOC CHEMISTRY, 2011, [Peer-reviewed]
    English, Recent progress observed in Topological Polymer Chemistry is outlined with particular emphasis on single-cyclic (ring) and multi-cyclic polymers having programmed chemical structures, now becoming obtainable with guaranteed purity by newly developed synthetic protocols. By making use of these topological polymers, unprecedented opportunities have now been realized to provide new insights on fundamental polymer properties either in solution or bulk, in static or dynamic states, or in self-assemblies. Moreover, unusual properties and functions for polymer materials have now been revealed based on their cyclic topologies, i.e., topology effects, unattainable either by linear or branched counterparts.
  • Emergence of Functionalities Originating from the Topology of Polymers
    Takuya Yamamoto
    KOBUNSHI RONBUNSHU, 68, 8, 550, 561, SOC POLYMER SCIENCE JAPAN, 2011, [Peer-reviewed]
    Japanese, Scientific journal, Cyclic polymers, possessing no chain ends, exhibit chemical and physical properties that can be distinguished from the linear counterparts. The synthesis of cyclic polymers has been pursued, and their functionalities arising from the unique shapes, namely topology effects, have been investigated. The ESA-CF process in conjunction with click chemistry selectively constructed a variety of unprecedented multicyclic topologies of polymers such as bridged- and spiro-types. It was demonstrated that cooperative electrostatic and hydrogen-bonding self-assembly followed by covalent conversion is an effective means for the synthesis of polymeric catenanes. The self-assembly of a cyclic amphiphilic block copolymer, prepared by intramolecular metathesis, gave a micelle with an approximately 50 C increase in the thermal stability in comparison with one formed from the linear precursor. Furthermore, linear and cyclic polymers containing a perylene diimide unit were synthesized, and single-molecule spectroscopy revealed the different diffusion modes of the polymers on the basis of their topology.
  • Topological Polymer Chemistry: New Synthesis of Cyclic and Multicyclic Polymers and Topology Effects Thereby
    Takuya Yamamoto, Yasuyuki Tezuka
    KOBUNSHI RONBUNSHU, 68, 12, 782, 794, SOC POLYMER SCIENCE JAPAN, 2011, [Peer-reviewed]
    Japanese, Scientific journal, Recent progress in topological polymer chemistry has been outlined. First, we focus on recent developments in an "electrostatic self-assembly and covalent fixation (ESA-CF)" process in conjunction with effective linking/cleaving chemistry including a metathesis process and an alkyne-azide click reaction. A variety of novel cyclic polymers having specific functional groups and unprecedented multicyclic macromolecular topologies have been realized by combining intriguing synthetic protocols. By making use of these topological polymers, unprecedented opportunities have now been realized to provide new insights on fundamental polymer properties either in solution or bulk, in static or dynamic states, or in self-assemblies. Moreover, unusual properties and functions for polymer materials have now been revealed based on their cyclic topologies, i.e., topology effects, unattainable either by linear or branched counterparts.
  • Effective Click Construction of Bridged- and Spiro-Multicyclic Polymer Topologies with Tailored Cyclic Prepolymers (kyklo-Telechelics)
    Naoto Sugai, Hiroyuki Heguri, Kengo Ohta, Qingyuan Meng, Takuya Yamamoto, Yasuyuki Tezuka
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 132, 42, 14790, 14802, AMER CHEMICAL SOC, Oct. 2010, [Peer-reviewed]
    English, Scientific journal, An alkyne-azide addition, i.e., click, reaction in conjunction with an electrostatic self-assembly and covalent fixation (ESA-CF) process has been demonstrated to effectively construct a variety of unprecedented multicyclic polymer topologies. A series of single cyclic poly(tetrahydrofuran), poly(THF), precursors having an alkyne group (Ia), an azide group (Ib), two alkyne groups at the opposite positions (Ic), and an alkyne group and an azide group at the opposite positions (Id) have been prepared by the ESA-CF process. Moreover, a bicyclic 8-shaped precursor having two alkyne groups at the opposite positions (Ie) was synthesized. The subsequent click reaction of la with linear (IIa) and three-armed star (IIb) telechelic precursors having azide groups has been performed to construct bridged-type two-way (IIIa) and three-way (IIIb) paddle-shaped polymer topologies, respectively. Likewise, spiro-type tandem tricyclic (IVa) and tetracyclic (IVb) topologies resulted from Ib/Ic and Ib/Ie, respectively. Furthermore, three types of multicyclic topologies that are composed of repeating ring (Va), alternating ring/linear (Vb), and alternating ring/star (Vc) units have been synthesized from Id, Ic/IIa, and Ic/IIb, respectively.
  • Synthesis and Topological Conversion of an 8-shaped Poly(THF) Having a Metathesis-Cleavable Unit at the Focal Position
    Kazuyuki Ishikawa, Takuya Yamamoto, Hiroyuki Harada, Yasuyuki Tezuka
    MACROMOLECULES, 43, 17, 7062, 7067, AMER CHEMICAL SOC, Sep. 2010, [Peer-reviewed]
    English, Scientific journal, A pair of 8-shaped poly(tetrahydrofuran)s, poly(THF)s, having a metathesis-cleavable olefinic unit of isomeric forms at the focal position, IIa and IIb, has been synthesized through an electrostatic self-assembly and covalent fixation (ESA-CF) process using a telechelic poly(THF) having N-phenylpyrrolidinium salt groups carrying a tetracarboxylate counteranion containing a trans-3-hexenyl group, as equilibrated isomeric forms of Ia and Ib. The subsequent metathesis cleavage reaction of the olefinic group in ha and lib has been conducted with a second generation Grubbs catalyst in the presence of ethyl vinyl ether. The polymer topology was thus converted from a dicyclic 8-shape into two simple loops having the two distinctive sizes consisting of one and two prepolymer units, IIIa and IIIb, respectively, corresponding to the linking mode of the two prepolymer segments on the pair of carboxylate groups at either the neighboring or the remote sites of the tetracarboxylate. Moreover, MALDI-TOF mass analysis has been performed for a series of the SEC-fractionated metathesis cleavage products. The absence of any fraction corresponding to polymeric [2]catenane products implies that the entanglement of the two prepolymer segments does not occur even though they are placed spatially close to each other.
  • Topology-Directed Control on Thermal Stability: Micelles Formed from Linear and Cyclized Amphiphilic Block Copolymers
    Satoshi Honda, Takuya Yamamoto, Yasuyuki Tezuka
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 132, 30, 10251, 10253, AMER CHEMICAL SOC, Aug. 2010
    English, Scientific journal, The thermal stability of a self-assembled micelle was remarkably enhanced by a topology effect. Linear poly(butyl acrylate)-block-poly(ethylene oxide)-block-poly(butyl acrylate) (1) and the cyclized product, poly(butyl acrylate)-block-poly(ethylene oxide) (2), were self-assembled to form flower-like micelles. By means of viscometry, the critical micelle concentrations were determined to be 0.13 and 0.14 mg/mL for 1 and 2, respectively. Dynamic light scattering, atomic force microscopy, and transmission electron microscopy studies revealed that both micelles are spherical and approximately 20 nm in diameter. Despite no distinctive change in the chemical composition or structure of the micelle, we found that the cloud point (T(c)) was elevated by more than 40 degrees C through the linear-to-cyclic topological conversion of the polymer amphiphile. Furthermore, the T(c) was tuned by coassembly of 1 and 2.
  • Construction of a Thermostable Micelle by Self-Assembly of a Cyclized Polymer
    Takuya Yamamoto, Satoshi Honda, Yasuyuki Tezuka
    Polym. Prepr., 51, 365, 366, 2010, [Peer-reviewed]
    English, International conference proceedings
  • 見える!リングポリマー分子の「かたち」と「うごき」――高分子トポロジー化学の新展開               
    Yamamoto Takuya
    化学, 65, 70, 71, 2010, [Invited]
    Japanese, Scientific journal
  • Effective Synthesis of Polymer Catenanes by Cooperative Electrostatic/Hydrogen-Bonding Self-Assembly and Covalent Fixation
    Kazuyuki Ishikawa, Takuya Yamamoto, Masumi Asakawa, Yasuyuki Tezuka
    MACROMOLECULES, 43, 1, 168, 176, AMER CHEMICAL SOC, Jan. 2010
    English, Scientific journal, The cooperative electrostatic and hydrogen-bonding self-assembly of polymer precursors a and the Subsequent covalent conversion have been demonstrated as ail effective means for the synthesis of polymer catenanes. Thus, a cyclic poly(tetrahydrofuran), poly(THF), having a hydrogen-bonding, isophthaloylbenzylic amide group (1) was prepared through in electrostatic self-assembly, and covalent fixation with a telechelic poly(THF) having N-phenylpyrrolidinium salt groups carrying a dicarboxylate counteranion containing the hydrogen-bonding unit (1). Another telechelic poly(THF) having,in isophthaloylbenzylic amide group at the center position and having N-phenylpyrrolidinium salt end groups carrying a biphenyldicarboxylate counteranion, 2, was subsequently prepared and subjected to a covalent conversion reaction in the presence of the preformed cyclic poly(THF) having a hydrogen-bonding unit (1). A polymer [2]catenane comprised of the two different cyclic poly(THF) components, I and II (from 2), has been isolated up to 7% yield as ail acetone-insoluble fraction and unequivocally characterized by means of MALDI TOF mass spectroscopy together with (1)H NMR and SEC techniques.
  • Multimode Diffusion of Ring Polymer Molecules Revealed by a Single-Molecule Study
    Satoshi Habuchi, Norihiro Satoh, Takuya Yamamoto, Yasuyuki Tezuka, Martin Vacha
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 49, 8, 1418, 1421, WILEY-V C H VERLAG GMBH, 2010
    English, Scientific journal
  • Recent Developments in the Synthesis of Cyclic Polymers by Ring-Expansion Polymerization
    Takuya Yamamoto
    JOURNAL OF SYNTHETIC ORGANIC CHEMISTRY JAPAN, 67, 9, 947, 948, SOC SYNTHETIC ORGANIC CHEM JPN, Sep. 2009, [Peer-reviewed], [Invited]
    Japanese, Scientific journal, Cyclic polymers can be effectively synthesized by ring-expansion polymerization, which does not cause random catenation even under undiluted conditions. This mini review focuses on recently developed controlled ring-expansion polymerizations.
  • Coordination-driven face-directed self-assembly of trigonal prisms. Face-based conformational chirality
    Douglas C. Caskey, Takuya Yamamoto, Chris Addicott, Richard K. Shoemaker, Jaroslav Vacek, Adam M. Hawkridge, David C. Muddiman, Gregg S. Kottas, Josef Michl, Peter J. Stang
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 130, 24, 7620, 7628, AMER CHEMICAL SOC, Jun. 2008
    English, Scientific journal, The coordination-driven self-assembly of four different trigonal prisms from 3 equiv of one of four different tetrapyridyl star connectors and 6 equiv of a platinum linker dication in nitromethane is presented. This face-directed approach affords high yields without template assistance. The prisms have been characterized by multinuclear and DOSY NMR and dual ESI-FT-ICR mass spectrometry. The use of a conformationally chiral star connector leads to a conformationally chiral prism when connector arm ends attached to a vertex have a strongly correlated twist sense and chirality is communicated across polyhedral faces, edges, and vertices. Molecular mechanics results suggest that in the smallest prism 3d collective effects dominate and the all-P and all-M conformers are strongly favored. NMR data prove that the two edges of the pyridine rings in the triflate salts of 3a-3d are distinct. An Eyring plot of rates obtained from line-shape analysis and 1-D EXCHSY NMR yields an activation enthalpy Delta H(double dagger) of similar to 12 kcal/mol and activation entropy Delta S(double dagger) of similar to-15 cal/mol.K for the edge interconversion process, compatible with pyridine rotation around the Pt-N bond. For 3c, this behavior is observed only up to similar to 318 K. At higher temperatures, the Eyring plot is again linear but follows a very different straight line, with a Delta H(double dagger) of similar to 35 kcal/mol and Delta S(double dagger) of similar to 60 cal/mol.K. This highly unusual result is further investigated and discussed in the following companion paper.
  • Radially diblock nanotube: site-selective functionalization of a tubularly assembled hexabenzocoronene.
    Justin L Mynar, Takuya Yamamoto, Atsuko Kosaka, Takanori Fukushima, Noriyuki Ishii, Takuzo Aida
    Journal of the American Chemical Society, 130, 5, 1530, 1, 06 Feb. 2008, [International Magazine]
    English
  • Self-Assembled Nanotubes and Nanocoils from pi-Conjugated Building Blocks
    Takuya Yamamoto, Takanori Fukushima, Takuzo Aida
    SELF-ASSEMBLED NANOMATERIALS II: NANOTUBES, 220, 1, 27, SPRINGER-VERLAG BERLIN, 2008
    English, In book, This review article describes recent studies on the self-assembly and co-assembly of pi-conjugated molecules into nanotubes and nanocoils. Such pi-conjugated molecules include phenylenes, phenylene vinylenes, phenylene ethynylenes, porphyrins, phthalocyanines, and polycyclic aromatic hydrocarbons, which are properly modified with hydrophilic and/or hydrophobic side chains for cooperative interactions. Not only nanocoils but also most reported nanotubes possess a helical chirality. These assembling events possibly show chiral amplification, where one-handedness can be realized even from stereochemically impure components (majority rule). Combination of components leading to non-tubular assemblies with properly chosen chiral components may give rise to nanotubes or nanocoils with one-handed helical chirality (sergeants-and-soldiers effect). Covalent modification of assembled components can enhance physical robustness against heating and solvolysis.
  • Conductive one-handed nanocoils by coassembly of hexabenzocoronenes: control of morphology and helical chirality.
    Takuya Yamamoto, Takanori Fukushima, Atsuko Kosaka, Wusong Jin, Yohei Yamamoto, Noriyuki Ishii, Takuzo Aida
    Angewandte Chemie (International ed. in English), 47, 9, 1672, 5, 2008, [International Magazine]
    English
  • Self-Assembled Nanotubes and Nanocoils from pi-Conjugated Building Blocks
    Takuya Yamamoto, Takanori Fukushima, Takuzo Aida
    SELF-ASSEMBLED NANOMATERIALS II: NANOTUBES, 220, 1, 27, SPRINGER-VERLAG BERLIN, 2008, [Peer-reviewed]
    English, In book, This review article describes recent studies on the self-assembly and co-assembly of pi-conjugated molecules into nanotubes and nanocoils. Such pi-conjugated molecules include phenylenes, phenylene vinylenes, phenylene ethynylenes, porphyrins, phthalocyanines, and polycyclic aromatic hydrocarbons, which are properly modified with hydrophilic and/or hydrophobic side chains for cooperative interactions. Not only nanocoils but also most reported nanotubes possess a helical chirality. These assembling events possibly show chiral amplification, where one-handedness can be realized even from stereochemically impure components (majority rule). Combination of components leading to non-tubular assemblies with properly chosen chiral components may give rise to nanotubes or nanocoils with one-handed helical chirality (sergeants-and-soldiers effect). Covalent modification of assembled components can enhance physical robustness against heating and solvolysis.
  • Stabilization of a kinetically favored nanostructure: surface ROMP of self-assembled conductive nanocoils from a norbornene-appended hexa-peri-hexabenzocoronene.
    Takuya Yamamoto, Takanori Fukushima, Yohei Yamamoto, Atsuko Kosaka, Wusong Jin, Noriyuki Ishii, Takuzo Aida
    Journal of the American Chemical Society, 128, 44, 14337, 40, 08 Nov. 2006, [International Magazine]
    English, Newly designed norbornene-appended hexabenzocoronene 1 self-assembles, upon diffusion of an Et(2)O vapor into its CH(2)Cl(2) solution, to form either graphitic nanocoils or nanotubes, depending on the self-assembling conditions. The coiled assembly, selectively formed at 15 degrees C, is a kinetic intermediate for the tubular assembly and transforms into nanotubes on standing at 25 degrees C. However, post-ring-opening metathesis polymerization of the norbornene pendants of 1 enhances the thermal stability of the coiled assembly as well as the tubular one and disables a thermodynamic coil-to-tube transition. The polymerized nanocoils show an electroconductivity of 1 x 10(-)(4) S cm(-)(1) upon doping with I(2), while the nonpolymerized nanocoils are disrupted upon being doped.
  • Self-assembly of amphiphilic hexabenzocoronenes with norbornene functionalities: Formation of nanocoil and nanotube and subsequent structural stabilization via ROMP
    Takuya Yamamoto, Takanori Fukushima, Wusona Jin, Yuki Suna, Norivuki Ishii, Takuzo Aida
    Polymer Preprints, Japan, 55, 1, 260, 2006, [Peer-reviewed]
    International conference proceedings, Nanotube and nanocoil with π-stacked graphitic arrays were selectively synthesized by the controlled self-assembly of a Gemini-shaped amphiphilic hexabenzocoronene possessing two norbornene functionalities at the termini of the hydrophilic chains. These nanostructures were covalently stabilized by surface polymerization via ROMP. On the other hand, when a hexabenzocoronene derivative with single norbornene functionality was subjected to ROMP, self-assembly took place to form a nanocoil with a polymerized surface.
  • Self-assembly of nanoscale supramolecular truncated tetrahedra
    M Schweiger, T Yamamoto, PJ Stang, D Blaser, R Boese
    JOURNAL OF ORGANIC CHEMISTRY, 70, 12, 4861, 4864, AMER CHEMICAL SOC, Jun. 2005
    English, Scientific journal, Two nanoscale truncated tetrahedra were synthesized via Pt(II)-mediated self-assembly. The first resulted from the reaction of 3 equiv of cis-Pt(PMe3)(2)(OTf)(2) and 2 equiv of 1,3,5-tris(4-pyridylethynyl)benzene, giving a truncated tetrahedron with a diameter of approximately 25 A. The second, analogous structure was obtained by the self-assembly of cis-Pt(PMe3)2(OTf)2 and 1,3,5-tris(4-pyridyl-trans-ethenyl)benzene. These two truncated tetrahedra were crystallized after partially exchanging the counterion to cobalticarborane for the X-ray structural analysis.
  • Synthesis of a bis(pyridyl)-substituted perylene diimide ligand and incorporation into a supramolecular rhomboid and rectangle via coordination driven self-assembly
    C Addicott, Oesterling, I, T Yamamoto, K Mullen, PJ Stang
    JOURNAL OF ORGANIC CHEMISTRY, 70, 3, 797, 801, AMER CHEMICAL SOC, Feb. 2005
    English, Scientific journal, The synthesis of a bis(pyridyl)-substituted perylene diimide ligand and its incorporation into a supramolecular rhomboid and rectangle via platinum-mediated self-assembly is reported. Both ensembles are characterized by multinuclear NMR and electrospray ionization mass spectrometry. In addition, the UV/vis spectra of the ensembles exhibit displaced and enhanced absorptions relative to the starting ligand. Size estimations using MM2 simulations show the assemblies are almost 46 Angstrom in length.
  • Self-assembly of flexible supramolecular metallacyclic ensembles: Structures and adsorption properties of their nanoporous crystalline frameworks
    B Chatterjee, JC Noveron, MJE Resendiz, J Liu, T Yamamoto, D Parker, M Cinke, CV Nguyen, AM Arif, PJ Stang
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 126, 34, 10645, 10656, AMER CHEMICAL SOC, Sep. 2004
    English, Scientific journal, The syntheses, structures, and N-2 adsorption properties of six new supramolecular metallacycles are reported. Flexible ditopic linkers, 1-4, with systematically varied lengths and conformational degrees of freedom were synthesized utilizing ester linkages. They were used in combination with (dppp)M(OTf)(2), where M = Pt(II) and Pd(II), and cis-(Me3P)(2)Pt(OTf)(2) to form flexible supramolecular metallacycles 5-10 in 88-98% isolated yields. Their structures were characterized via multinuclear NMR and X-ray crystallography. The metallacycles stack to form porous structures in the crystalline state. The pore dimensions depend on both the phosphorus ligands attached to the metals and the flexible linkers. Adsorption studies on the porous materials show that Sa, 6, 8, and 9 held 11.7, 16.5, 5.7, and 6.8 cm(3)/g STP of N-2 at 77 K, respectively. A guest-exchange study with nitromethane and toluene reveals that the nanopore in 5 is flexible, a property which was transferred from the linker to the supramolecular structure in the solid state.
  • Dynamic equilibrium of a supramolecular dimeric rhomboid and trimeric hexagon and determination of its thermodynamic constants
    T Yamamoto, AM Arif, PJ Stang
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 125, 40, 12309, 12317, AMER CHEMICAL SOC, Oct. 2003
    English, Scientific journal, A supramolecular dimeric rhomboid and its trimeric counterpart, a hexagon, are generated by design via the directional bonding methodology of self-assembly. The different-sized supramolecular macrocycles formed by Pt-coordination undergo a concentration- and temperature-dependent dynamic equilibrium. The two structures are characterized by multinuclear NMR and ESI-MS. Extensive study of the dynamic equilibrium of the two species in solution is performed to obtain its thermodynamic properties. By varying the ionic strength, mu, of the solutions, the true thermodynamic equilibrium constant, K, is determined at each experimental temperature (K-253 = 36 +/- 7, K-273 = 18 +/- 6, K-293 = 10 +/- 3, K-313 = 9 +/- 2, K-333 = 5 +/- 2, and K-353 = 3.0 +/- 0.2). By applying these values of true K at the respective temperatures to the van't Hoff equation extended with the entropy term, the standard enthalpy and entropy changes are determined for the equilibrium: with DeltaHdegrees = -18 +/- 1 kJ mol(-1) and DeltaSdegrees = -43 +/- 4 J mol(-1) K-1, respectively, for the forward reaction (rhomboid to hexagon) of the equilibrium. The rhomboid is selectively crystallized, and its crystal structure is determined by X-ray diffraction. The structure reveals a significant amount of porosity as well as distortion of the rhomboid from planarity, leading to channels that can be observed from two viewing positions of the packing.
  • Self-assembly of molecular prisms via an organometallic "clip"
    CJ Kuehl, T Yamamoto, Seidel, SR, PJ Stang
    ORGANIC LETTERS, 4, 6, 913, 915, AMER CHEMICAL SOC, Mar. 2002
    English, Scientific journal, [GRAPHICS]
    Under the appropriate conditions, the combination of two tritopic pyridyl ligands with three metal-containing molecular "clips" spontaneously generates supramolecular coordination cages with trigonal prismatic frameworks.

Other Activities and Achievements

Books and other publications

  • 基礎高分子科学第2版               
    Yamamoto Takuya
    東京化学同人, Jan. 2020, [Contributor]
  • 環状高分子の合成と機能発現               
    Yamamoto Takuya, 環状高分子が形作る分子集合体の機能
    シーエムシー出版, 2018, [Contributor]
  • ナノテクノロジーが拓く未来の医療               
    Yamamoto Takuya, 環状高分子を利用した新奇ナノメディシン材料
    丸善出版, 2017, [Contributor]
  • クリックケミストリー−基礎から実用まで−               
    山本拓矢, 手塚育志, トポロジカル高分子の合成
    シーエムシー出版, 2014, [Contributor]
  • Topological polymer chemistry : progress of cyclic polymers in syntheses, properties, and functions
    Baba, E, Yamamoto, T, Self-Assembly and Functions of Cyclic Polymers
    World Scientific, 2013, 9789814401272, English
  • Synthesis of polymers : new structures and methods set
    Yamamoto, T, Tezuka, Y, Multicyclic Polymers
    Wiley-VCH, 2012, 9783527327577, English, [Joint work]
  • Complex macromolecular architectures : synthesis, characterization, and self-assembly
    Yamamoto, T, Tezuka, Y, Cyclic and Multicyclic Topological Polymers
    John Wiley & Sons, 2011, 9780470825136, English, [Contributor]
  • 有機貯蔵材料とナノ技術−水素社会に向けて−               
    山本拓矢, 福島孝典, 相田卓三, π電子系分子の自己組織化による中空ナノ構造体の構築とその機能
    シーエムシー出版, 2007, [Contributor]

Lectures, oral presentations, etc.

  • Cyclic Polymers Synthesis and Characterization               
    Yamamoto Takuya
    The Second International Conference of Polymeric and Organic Materials in Yamagata University, 18 Dec. 2019, English, Invited oral presentation
    [Invited], [International presentation]
  • Cyclic Polymer Synthesis and Their Unique Characteristics               
    Yamamoto Takuya
    18 Nov. 2019, English, Public discourse
    POSTECH, [Invited], [International presentation]
  • Synthesis of Cyclic Polymers and Their Unique Properties               
    Yamamoto Takuya
    Korea–Japan Joint Polymer Symposium on Polymer Science 2019, 19 Sep. 2019, English, Invited oral presentation
    [Invited], [International presentation]
  • Advanced Synthesis of Cyclic Polymers and Their Unique Characteristics               
    Yamamoto Takuya
    Polymers and Networks via Topology and Entanglement, 07 Aug. 2019, English, Invited oral presentation
    [Invited], [International presentation]
  • 環状P3HTを用いたカーボンナノチューブの分散と画像認識による高分子トポロジーの識別               
    Yamamoto Takuya
    次世代物質探索のための離散幾何学 研究成果発表会, 03 Aug. 2019, Japanese, Invited oral presentation
    [Invited], [Domestic Conference]
  • Synthesis and Unique Properties of Cyclic Polymers               
    Yamamoto Takuya
    2nd Asian–French Workshop on Polymer Science, 19 Jul. 2019, English, Invited oral presentation
    [Invited], [International presentation]
  • Synthesis and Properties of Defect-Free Cyclic P3HT               
    Yamamoto Takuya
    National Central University–Hokkaido University Joint Symposium, 11 Jun. 2019, English, Invited oral presentation
    [Invited], [International presentation]
  • Novel Synthesis and Unique Characteristics of Cyclic Polymers               
    Yamamoto Takuya
    Polymers Meet Topology, 01 Feb. 2019, English, Invited oral presentation
    [Invited], [International presentation]
  • 環状高分子を利用した新奇刺激応答型DDS材料の開発               
    Yamamoto Takuya
    「産業基盤の創生」成果報告会(臨時), 04 Oct. 2018, Japanese, Others
    キヤノングローバル戦略研究所, 東京, [Invited], [Domestic Conference]
  • 環状高分子を利用した界面制御               
    Yamamoto Takuya
    第6回「未来のコロイドおよび界面化学を創る若手討論会」, 17 Sep. 2018, Japanese, Invited oral presentation
    つくば国際会議場, つくば, [Invited], [Domestic Conference]
  • Synthesis and Self-Assembly of Cyclic Polymers and Structural Analysis of the Molecular Aggregates               
    Yamamoto Takuya
    7th Synchrotron Radiation in Polymer Science, 06 Sep. 2018, English, Invited oral presentation
    Hwabaek International Convention Center, Gyeongju, Korea, [Invited], [International presentation]
  • Functional Materials Formed from Cyclic Polymers               
    Yamamoto Takuya
    Japan–Korea Joint Polymer Symposium on Polymer Science 2018, 26 Jul. 2018, English, Invited oral presentation
    Hokkaido University, Sapporo, Japan, [Invited], [International presentation]
  • Synthesis of Cyclic Polymers and Control of Their Properties               
    Yamamoto Takuya
    255th ACS National Meeting, 21 Mar. 2018, English, Invited oral presentation
    New Orleans, U.S.A., [Invited], [International presentation]
  • 環状高分子を利用した新奇機能性ソフトマテリアルの開発               
    Yamamoto Takuya
    第68回コロイドおよび界面化学討論会, 08 Sep. 2017, Japanese, Invited oral presentation
    神戸大学, 神戸, [Invited], [Domestic Conference]
  • 環状高分子を使用した機能材料開発               
    Yamamoto Takuya
    第161回東海高分子研究会講演会(夏期合宿), 01 Sep. 2017, Japanese, Invited oral presentation
    西浦温泉ホテルたつき, 蒲郡, [Invited], [Domestic Conference]
  • Development of Functional Materials by Cyclic Polymers               
    Yamamoto Takuya
    International Symposium on Advanced Polymeric Materials 2017, 28 Aug. 2017, English, Invited oral presentation
    New Huayuan Hotel, Changchun, China, [Invited], [International presentation]
  • Topology for Polymeric Materials               
    Yamamoto Takuya
    Knots and Polymers: Aspects of Topological Entanglement in DNA, Proteins and Graph-shaped Polymers, 08 Aug. 2017, English, Invited oral presentation
    Ochanomizu University, Tokyo, Japan, [Invited], [International presentation]
  • Self-Assembly and Topological Conversion of Cyclic Polymers               
    Yamamoto Takuya
    Invited Lecture, 25 Oct. 2016, English, Invited oral presentation
    Donghua University, Shanghai, China, [Invited], [International presentation]
  • Reversible Linear–Cyclic Topological Conversion of Telechelic Polymers by Photo- and Thermal Reactions               
    Yamamoto Takuya
    Symposium of Cyclic Polymer, 23 Oct. 2016, English, Invited oral presentation
    Soochow University, Suzhou, China, [Invited], [International presentation]
  • Reversible Topological Transformation to Form Cyclic Polymers by Heat- and Light-Triggered Reactions               
    Yamamoto Takuya
    Taiwan–Japan Bilateral Polymer Symposium 2016, 09 Sep. 2016, English, Invited oral presentation
    National Tsing Hua University, Hsinchu, Taiwan, [Invited], [International presentation]
  • 環状高分子の合成と機能の創出               
    Yamamoto Takuya
    31st Summer University in Hokkaido, 02 Sep. 2016, Japanese, Invited oral presentation
    定山渓ビューホテル, 札幌, [Invited], [Domestic Conference]
  • 環状高分子の集積に基づいた機能材料開発               
    Yamamoto Takuya
    伸長プロセス専門委員会, 30 Aug. 2016, Japanese, Invited oral presentation
    JSW, 室蘭, [Invited], [Domestic Conference]
  • Self-assembly and Topological Transformation of Cyclic Polymers               
    Yamamoto Takuya
    International Workshop on Topology and Graphs in Polymer Chemistry, 07 Aug. 2016, English, Invited oral presentation
    Tokyo Institute of Technology, Tokyo, Japan, [Invited], [International presentation]
  • Functional Materials by Self-Assembly of Cyclic Polymers               
    Yamamoto Takuya
    HU-NTU-CERMAV Joint Symposium on Functional Materials, 05 Aug. 2016, English, Invited oral presentation
    Hokkaido University, Sapporo, Japan, [Invited], [International presentation]
  • 環状両親媒性高分子によるベシクル構築とゲスト包摂による物性変化               
    Yamamoto Takuya
    生物規範工学 公開講演会, 04 Aug. 2016, Japanese, Invited oral presentation
    北海道大学, 札幌, [Invited], [Domestic Conference]
  • 環状両親媒性ブロック共重合体によるベシクルの構築               
    Yamamoto Takuya
    精密ネットワークポリマー研究会, 08 Jul. 2016, Japanese, Invited oral presentation
    東京工業大学, 東京, [Invited], [Domestic Conference]
  • 環状高分子の自己組織化と機能発現               
    Yamamoto Takuya
    第65回高分子学会年次大会, 25 May 2016, Japanese, Invited oral presentation
    神戸国際会議場・展示場, 神戸, [Invited], [Domestic Conference]
  • Topological Transformation and Self-Assembly of Cyclic Polymers               
    Yamamoto Takuya
    Japan–Korea Joint Symposium 2015, 29 Oct. 2015, English, Invited oral presentation
    Kitakyushu International Conference Center, Kitakyushu, Japan, [Invited], [International presentation]
  • 環状高分子の自己組織化による分子集合体の形成と機能発現               
    Yamamoto Takuya
    関東高分子若手研究会 サマーキャンプ2015, 04 Aug. 2015, Japanese, Invited oral presentation
    東京農工大学合宿宿泊施設館山荘, 館山, [Invited], [Domestic Conference]
  • Emerging Functionalities of Cyclic Polymers               
    Yamamoto Takuya
    Invited Lecture, 23 Mar. 2015, English, Invited oral presentation
    ETH Zürich, Zürich, Switzerland, [Invited], [International presentation]
  • Synthesis and Self-Assembly of Cyclic Polymers toward the Amplification of Topology Effects               
    Yamamoto Takuya
    Taiwan–Japan Bilateral Polymer Symposium-2014, 24 Nov. 2014, English, Invited oral presentation
    National Cheng Kung University, Tainan, Taiwan, [Invited], [International presentation]
  • Synthesis and Self-Assembly of Cyclic Polymers toward the Amplification of Topology Effects               
    Yamamoto Takuya
    Taiwan–Japan Bilateral Polymer Symposium-2014, 21 Nov. 2014, English, Invited oral presentation
    National Cheng Kung University, Tainan, Taiwan, [Invited], [International presentation]
  • 環状ポリ乳酸を利用した機能材料の開発               
    Yamamoto Takuya
    第15回リング・チューブ超分子研究会シンポジウム, 27 Oct. 2014, Japanese, Invited oral presentation
    東京工業大学, 東京, [Invited], [Domestic Conference]
  • 自己組織化による分子集合体の形成と機能発現               
    Yamamoto Takuya
    環状高分子が示すトポロジー効果の増幅, 22 Oct. 2014, Japanese, Invited oral presentation
    奈良先端科学技術大学院大学, 生駒, [Invited], [Domestic Conference]
  • 環状トポロジーを利用した高分子機能材料の開発               
    Yamamoto Takuya
    ISCセミナー, 09 Jun. 2014, Japanese, Invited oral presentation
    産業技術総合研究所, つくば, [Invited], [Domestic Conference]
  • 環状高分子が発現する機能特性の探求               
    Yamamoto Takuya
    ソフトインターフェースの分子科学 第10回領域会議, 17 Mar. 2014, Japanese, Invited oral presentation
    みのお山荘風の杜, 箕面, [Invited], [Domestic Conference]
  • Cyclized Amphiphilic Block Copolymers toward Controlled Release               
    Yamamoto Takuya
    BIT’s 3rd Annual Symposium of Drug Delivery Systems, 16 Nov. 2013, English, Invited oral presentation
    Hainan International Convention and Exhibition Center, Haikou, China, [Invited], [International presentation]
  • 環状高分子を利用した機能材料の創製               
    Yamamoto Takuya
    第80回高分子若手研究会[関西], 27 Jul. 2013, Japanese, Invited oral presentation
    関西セミナーハウス, 京都, [Invited], [Domestic Conference]
  • 環状トポロジーに由来する高分子機能材料の驚異的な特性               
    Yamamoto Takuya
    第59回高分子研究発表会(神戸) ヤングサイエンティスト講演, 12 Jul. 2013, Japanese, Invited oral presentation
    兵庫県民会館, [Invited], [Domestic Conference]
  • 環状高分子の自己組織化による機能発現               
    Yamamoto Takuya
    日本化学会第93春季年会(2013) 若い世代の特別講演会, 23 Mar. 2013, Japanese, Invited oral presentation
    立命館大学, 草津, [Invited], [Domestic Conference]
  • 環状高分子を利用したソフトマテリアルの創製               
    Yamamoto Takuya
    ソフトインターフェースの分子科学 第9回公開シンポジウム, 23 Jan. 2013, Japanese, Invited oral presentation
    タワーホール船堀, 東京, [Invited], [Domestic Conference]
  • 両親媒性環状ブロック共重合体の自己組織化による『トポロジー効果』の増幅と機能性ミセルの作製               
    Yamamoto Takuya
    ソフトインターフェースの分子科学 第8回領域会議, 27 Jul. 2012, Japanese, Invited oral presentation
    伝国の杜・置賜文化ホール, 米沢, [Invited], [Domestic Conference]
  • Self-Assembly of Cyclic Amphiphilic Block Copolymers and Development of Functions               
    Yamamoto Takuya
    Invited Lecture, 16 Jul. 2012, English, Invited oral presentation
    The University of Manchester, Manchester, U.K., [Invited], [International presentation]
  • Formation of a Micelle from an Amphiphilic Cyclic Block Copolymer and Determination of the Stability               
    Yamamoto Takuya
    MacroGroup UK International Conference on Polymer Synthesis & UKPCF International Conference on Polymer Colloids, 12 Jul. 2012, English, Invited oral presentation
    University of Warwick, Warwick, U.K., [Invited], [International presentation]
  • Self-Assembly of Cyclic Amphiphilic Block Copolymers and Development of Functions               
    Yamamoto Takuya
    Invited Lecture, 06 Jul. 2012, English, Invited oral presentation
    Ghent University, Ghent, Belgium, [Invited], [International presentation]
  • 環状ブロック共重合体の自己組織化によるミセルの構築と機能発現               
    Yamamoto Takuya
    九州地区高分子若手研究会・夏の講演会, 29 Jun. 2012, Japanese, Invited oral presentation
    ホテルクラウンパレス小倉, 小倉, [Invited], [Domestic Conference]
  • 自己組織化によるナノ構造体の構築と機能発現               
    Yamamoto Takuya
    分子ロボティクス研究会 2月定例研究会, 23 Feb. 2012, Japanese, Invited oral presentation
    東京工業大学, 東京, [Invited], [Domestic Conference]
  • 両親媒性ブロック共重合体の環状化による高分子ミセルの耐熱性および耐塩性の向上               
    Yamamoto Takuya
    トクヤマ科学技術振興財団 第14回研究成果報告会, 09 Dec. 2011, Japanese, Invited oral presentation
    トクヤマつくば研究所, つくば, [Invited], [Domestic Conference]
  • 高分子の『かたち』に基づく機能材料開発: DDSに向けた高分子ミセルの創製               
    Yamamoto Takuya
    平成23年度東工大挑戦的研究賞授賞式, 17 Oct. 2011, Japanese, Invited oral presentation
    東京工業大学, 東京, [Invited], [Domestic Conference]
  • 機能性環状高分子ミセルの開発               
    Yamamoto Takuya
    ソフトインターフェースの分子科学 第6回領域会議, 29 Jul. 2011, Japanese, Invited oral presentation
    九州大学, 春日, [Invited], [Domestic Conference]
  • Micelle from a Cyclic Block Copolymer: Stabilization via the "Topology Effect"               
    Yamamoto Takuya
    IPCG Polymer Colloids Conference 2011, 30 Jun. 2011, English, Invited oral presentation
    University of New Hampshire, Durham, U.S.A., [Invited], [Domestic Conference]
  • 高分子トポロジーの変換および自己組織化の連鎖的状態変化を利用した新規機能材料の創製               
    Yamamoto Takuya
    2009年度東京工業大学フロンティア研究センター ベンチャー・ビジネス・ラボラトリーシンポジウム, 19 Mar. 2010, Japanese, Invited oral presentation
    東京工業大学, 東京, [Invited], [Domestic Conference]
  • Thermostable Micelle by Self-Assembly of a Cyclized Block Copolymer               
    Yamamoto Takuya
    Korea–Japan Young Scientist Symposium, 05 Mar. 2010, English, Invited oral presentation
    KAIST, Daejeon, Korea, [Invited], [International presentation]
  • Construction of Topological Block Copolymers through Click Chemistry               
    Advanced Polymeric Materials and Technology symposium, 2010, Poster presentation
  • 環状構造を有する高分子の構築とトポロジー効果を利用した新規機能性の創製               
    関東高分子若手研究会, 2010
  • Construction of a Thermostable Micelle by Self-Assembly of a Cyclized Polymer               
    239th American Chemical Society National Meeting & Exposition, 2010
  • クリックケミストリーを用いた直列多環状高分子の合成               
    日本化学会第90回春季年会, 2010
  • 高分子間クリックケミストリーによるトポロジカルブロック交互共重合体およびγ-グラフ型高分子の合成               
    日本化学会第90春年会, 2010
  • 環状アルカンジスルフィドを用いた自己組織化単分子膜(SAM)の作成               
    日本化学会 第90春季年会, 2010, Poster presentation
  • 両親媒性環状ブロック共重合体による熱安定性に優れた新規高分子ミセルの創製               
    日本化学会第90春季年会 (2010), 2010
  • 環状高分子間のクリックケミストリーを用いた3環及び4環直列型ポリテトラヒドロフランの選択的構築               
    第59回高分子年次大会, 2010
  • クリックケミストリーおよびメタセシス反応を用いた環鎖トポロジカル交互共重合体およびγ-グラフ型高分子の合成               
    第59回高分子学会年次大会, 2010
  • 環状高分子の構造特性を利用した耐熱性に優れる高分子ミセルの創製               
    第59回 高分子学会年次大会, 2010
  • Construction of Topological Block Copolymers through Click Chemistry               
    Advanced Polymeric Materials and Technology symposium, 2010, Poster presentation
  • Construction of a Thermostable Micelle by Self-Assembly of a Cyclized Polymer               
    239th American Chemical Society National Meeting & Exposition, 2010
  • Preparation of self-assembled monolayers (SAMs) from cyclic alkanedisulfides               
    2010, Poster presentation
  • Construction of a thermostable micelle by a cyclized amphiphilic block copolymer               
    The 90th Annual Meeting of The Chemical, 2010
  • Formation of a Thermostable Polymeric Micelle from a Cyclized Block Copolymer               
    59th SPSJ Annual Meeting, 2010
  • 水素結合性ユニットを含む高分子の環化反応を利用したカテナンの合成               
    2009
  • Synthesis of Topological Block Copolymers via Click Chemistry               
    ADVANCED FUNCTIONAL MATERIALS CONFERENCE, 2009, Poster presentation
  • クリックケミストリーを用いた二環および三環パドル型高分子の合成               
    日本化学会第89春年会, 2009
  • Catenane Synthesis Via Cyclization of a Cyclic Polymer Through Hydrogen-Bonding/Electrostatic Self-Assembly               
    2009 Taiwan-Japan Bilateral Polymer Symposium, 2009
  • 両親媒性環状ブロック共重合体の合成とそのミセル形成               
    第58回 高分子学会年次大会, 2009, Poster presentation
  • 水素結合性ユニットを含む環状高分子を利用する非対称2-カテナンの合成               
    第58回 高分子学会年次大会, 2009, Poster presentation
  • 高分子間クリックケミストリーを用いた二環および三環パドル型高分子トポロジーの構築               
    第58回高分子学会年次大会, 2009, Poster presentation
  • 両親媒性環状ブロック共重合体による熱安定性に優れた高分子ミセルの構築-新規トポロジー効果の創製-               
    第58回 高分子学会討論会, 2009
  • ペリレンジイミド部位を持つ環状および直鎖状ポリテトラヒドロフランの単分子蛍光観察による拡散係数測定               
    第58回高分子討論会, 2009
  • Synthesis of a Hetero-Type 2-Catenane via the Cyclization of a Telechelic Polymer Having Hydrogen-Bonding Unit               
    Asia Nanotech Camp 2009, 2009
  • 水素結合性ユニットの自己組織化に基づくヘテロ型2-カテナンの合成               
    第58回 高分子討論会, 2009, Poster presentation
  • クリックケミストリーを用いた直列多環状高分子の合成               
    第58回高分子討論会, 2009, Poster presentation
  • クリックケミストリーを利用した多環状トポロジーPTHF の合成               
    第58回高分子討論会, 2009, Poster presentation
  • Formation of a Catenane via the Cyclization of a Telechelic Polymer Having a Hydrogen-Bonding Unit               
    The chemical society of Japan, The 89th Annual Meeting, 2009
  • Synthesis of Topological Block Copolymers via Click Chemistry               
    ADVANCED FUNCTIONAL MATERIALS CONFERENCE, 2009, Poster presentation
  • Catenane Synthesis Via Cyclization of a Cyclic Polymer Through Hydrogen-Bonding/Electrostatic Self-Assembly               
    2009 Taiwan-Japan Bilateral Polymer Symposium, 2009
  • Synthesis and micelle formation of amphiphilic cyclic block copolymers               
    2009, Poster presentation
  • Synthesis of a Dissymmetric 2-Catenane via the Cyclization of a Telechelic Polymer in the Presence of a Cyclic Polymer Having Hydrogen-Bondings               
    The Society Polymer Science, Japan, Annual Meeting, 2009, Poster presentation
  • Construction of Thermally Stable Micelles by Amphiphilic Cyclic Block Copolymers-Creation of New Topology Effects-               
    Polymer Preprints, 2009
  • Synthesis of a Hetero-Type 2-Catenane via the Cyclization of a Telechelic Polymer Having Hydrogen-Bonding Unit               
    Asia Nanotech Camp 2009, 2009
  • Synthesis of a Hetro-Type 2-Catenane via the Cyclization of a Telechelic Polymer Having Hydrogen-Bonding Unit               
    The Society Polymer science, Japan, Symposium on Macromolecules, 2009, Poster presentation
  • 自己組織化による超分子ナノ構造体の構築               
    Yamamoto Takuya
    第13回有機・高分子物質フォーラム, 15 Dec. 2008, Japanese, Invited oral presentation
    東京工業大学, 東京, [Domestic Conference]
  • ヘキサベンゾコロネン誘導体の自己集合化による導電性ナノコイルの構築:共自己組織化による形状とラセンキラリティーの同時制御               
    SORSTジョイントシンポジウム(8)「有機合成力」竏窒サのダイナミズム, 2008, Poster presentation
  • Formation of One-Handed Nanocoils by Coassembly of Hexabenzocoronene Derivatives               
    International Symposium on Engineering Micro-/Nano-Materials based on Self-Assembling and Self-Organization (ISEM 2008), 2008, Poster presentation
  • Click Chemistryを用いたヘキサベンゾコロネンナノチューブ内外表面への選択的官能基化               
    日本化学会第88春季年会, 2008
  • ヘキサベンゾコロネン誘導体の自己集合形態とラセンキラリティーの同時制御による一方巻きナノコイルの構築               
    第57回高分子学会年次大会, 2008, Poster presentation
  • クリックケミストリーを用いたポスト官能基化による径方向にジブロック構造を有するヘキサベンゾコロネンナノチューブの構築               
    第57回高分子学会年次大会, 2008
  • Formation of One-Handed Nanocoils by Self-Assembly of Norbornene-Appended Hexabenzocoronene Derivatives               
    Yamada Conference 2008, 2008, Poster presentation
  • Formation of a Catenane via the Cyclization of a Telechelic Polymer in the Presence of a Cyclic Polymer through Hydrogen-Bonding               
    Tokyo Tech-Asia Materials Week, 2008
  • Formation of One-Handed Nanocoils by Coassembly of Hexabenzocoronene Derivatives               
    International Symposium on Engineering Micro-/Nano-Materials based on Self-Assembling and Self-Organization (ISEM 2008), 2008, Poster presentation
  • Formation of One-Handed Nanocoils by Self-Assembly of Norbornene-Appended Hexabenzocoronene Derivatives               
    Yamada Conference 2008, 2008, Poster presentation
  • Formation of a Catenane via the Cyclization of a Telechelic Polymer in the Presence of a Cyclic Polymer through Hydrogen-Bonding               
    Tokyo Tech-Asia Materials Week, 2008
  • Formation of Nanocoils and Nanotubes via the Self-Assembly of Norbornene-Appended Amphiphilic Hexabenzocoronene Derivatives               
    6th Nanoarchitectonics Workshop 2007 "One-Dimensional Nanostructures for Nanoarchitectonics" (ODNN 2007), 2007, Poster presentation
  • ノルボルネンを末端に持つ両親媒性ヘキサベンゾコロネン誘導体の自己組織化によるナノコイルとナノチューブの形成               
    日本化学会第87春季年会, 2007
  • ヘキサベンゾコロネン誘導体の自己集合化によるナノコイルの生成:不斉増幅現象が引き起こすラセン巻き方向の制御               
    第56回高分子学会年次大会, 2007
  • Helical Nanoarchitectures by Programmed Self-Assembly of Norbornene-Appended Hexabenzocoronene Derivatives               
    Chirality at the Nanoscale, 2007
  • ヘキサベンゾコロネン誘導体の自己集合化による片方巻きナノコイルの生成               
    第37回構造有機化学討論会, 2007, Poster presentation
  • Formation of Nanocoils and Nanotubes via the Self-Assembly of Norbornene-Appended Amphiphilic Hexabenzocoronene Derivatives               
    6th Nanoarchitectonics Workshop 2007 "One-Dimensional Nanostructures for Nanoarchitectonics" (ODNN 2007), 2007, Poster presentation
  • Helical Nanoarchitectures by Programmed Self-Assembly of Norbornene-Appended Hexabenzocoronene Derivatives               
    Chirality at the Nanoscale, 2007
  • Programmed Self-Assembly toward New -Electronic Nanoarchitectures               
    Yamamoto Takuya
    Invited Lecture, 05 Jun. 2006, English, Invited oral presentation
    Tokyo Institute of Technology, Tokyo, [Invited], [International presentation]
  • 両親媒性ヘキサベンゾコロネンを側鎖に有するポリノルボルネンの自己組織化によるナノコイルの形成               
    日本化学会第86春季年会, 2006
  • Programmed Self-Assembly toward New π-Electronic Nanostructures               
    2006
  • ノルボルネンを有する両親媒性ヘキサベンゾコロネンの自己組織化:ナノコイルおよびナノチューブの生成とROMPによる構造安定化               
    第55回高分子学会年次大会, 2006
  • ヘキサベンゾコロネン誘導体の自己集合化によるラセンナノコイルの生成と不斉増幅現象               
    第55回高分子討論会, 2006
  • Programmed Self-Assembly toward New π-Electronic Nanostructures               
    2006
  • Equilibrium of a Supramolecular Dimer and Trimer and Determination of Its Thermodynamic Constants               
    226th ACS National Meeting, 2003, Poster presentation
  • Equilibrium of a Supramolecular Dimer and Trimer and Determination of Its Thermodynamic Constants               
    226th ACS National Meeting, 2003, Poster presentation
  • Self-Assembly of Nanoscale Truncated Tetrahedra by Coordination Chemistry               
    37th National Organic Symposium, 2001, Poster presentation
  • Self-Assembly of Nanoscale Truncated Tetrahedra by Coordination Chemistry               
    37th National Organic Symposium, 2001, Poster presentation

Affiliated academic society

  • 日本化学会               
  • 高分子学会               
  • The Chemical Society of Japan               
  • The Society of Polymer Science, Japan               

Research Themes

  • Functional Design of Nanofibers Based on the Synergetic Effects of Hydrogen/Deuterium Exchange and Polymer Chain Confinement
    Grants-in-Aid for Scientific Research
    01 Apr. 2023 - 31 Mar. 2027
    松本 英俊, 山本 拓矢, 宝田 亘
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Tokyo Institute of Technology, 23H02022
  • Design of block copolymer to create single-nanosized microphase structure
    Grants-in-Aid for Scientific Research
    01 Apr. 2019 - 31 Mar. 2022
    Satoh Toshifumi
    This study aims to establish new methodologies for controlling the periodicity (domain-spacing) of the microphase-separated structure formed by block copolymers (BCP) to about 5 nm. As a methodology to achieve this, in this study, we mainly examined (1) the restriction of the polymer chain dimension by introducing intramolecular cross-linking into BCP and (2) the introduction of macrocyclic units into BCP. As a result, in the methodology (1), the introduction of intramolecular cross-linking succeeded in reducing the domain-spacing by up to 47%, and in the methodology (2), the domain-spacing was reduced by up to 76% as compared with the corresponding linear BCP.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 19H02769
  • Construction of a soft giant cage-like molecular system consisting of polymer chains
    Grants-in-Aid for Scientific Research
    28 Jun. 2019 - 31 Mar. 2021
    Satoh Tofhifumi
    Cage-shaped nanoobjects which composed of synthetic soft polymer framework was successfully synthesized and subjected to structural analysis. The three-armed cage-shaped polycaprolactone as a model macromolecule was synthesized and characterized by small-angle X-ray scattering experiment in solution state, which revealed that the cage-shaped macromolecule had a unique folded dimension as compared to the linear counterpart. In addition, we have established a cyclopolymerization strategy to graft polymers with densely arrayed cage-shaped PCL side chains. This synthetic method allowed the control of number of cage-shaped units of graft polymers, which enabled systematic characterization. Since all the synthetic method that we used can be applicable to diverse polymer species, the cage-shaped nanoobjects with desired number of cage-shaped units will be easily obtained. The cage-shaped nanoobjects with soft polymeric framework could be new promising candidate for materials application.
    Japan Society for the Promotion of Science, Grant-in-Aid for Challenging Research (Exploratory), Hokkaido University, 19K22209
  • 数学的アプローチによる新奇超分子系材料創成と解析
    科学研究費助成事業
    01 Apr. 2018 - 31 Mar. 2020
    山本 拓矢
    本研究課題において、環状高分子とカーボンナノチューブ(CNT)との複合化・ネットワーク化による高分子トポロジーに立脚した高分散安定化現象を、領域内の共同研究を通して数学・情報学的基盤に基づき解明し、その応用として新規材料の開発を試みた。
    まず、完全共役構造を有する環状Poly(3-Hexylthiophene)(P3HT)の合成に成功し、これがCNTに対し優れた分散安定性を付与することを見出した。さらに、P3HTのトポロジー(直鎖または環)に依存したCNTの分散安定化を定量的に評価するために、領域内共同研究によってTEM画像の情報学的解析を行った。つまり、P3HTのトポロジーに依存したCNTの分散安定化を、畳み込みニューラルネットワークを用いた機械学習により評価する方法を見出た。ここで、環状高分子がナノ構造体を高分散安定化する原理の解明と新奇機能材料開発のために、CNT上のP3HTネットワークおよび複合材料中のCNTネットワークの階層構造解析として、CNTとP3HT複合体のTEM画像の分析に際して、その分散性を目視で見積もり、P3HTのトポロジーを評価する手法には客観性と正確さに限界があった。そのため、畳み込みニューラルネットワークによる機械学習を用いて、中程度の精度(62~80%)ながら画像から構成成分(直鎖状P3HTまたは環状P3HT)を見極める手法を開発した。この手法の実用化と汎用化に向け、P3HTの分子量やCNTの直径を変化させて同様のTEM画像解析を行い、これらの要因がどのように解析精度に影響するのか精査した。また、CNTと環状P3HT複合構造の高分解能TEMを測定したところ、CNTを構成する炭素原子も確認できるほど分解能で、高分子1本1本が観察できた。
    さらに、本研究期間の成果として1本の高分子鎖に複数の異なる官能基を導入し、その折りたたみ様式を制御することで異なる2環状トポロジー(8の字型、θ型、および手錠型)を選択的に構築した。
    日本学術振興会, 新学術領域研究(研究領域提案型), 北海道大学, 18H04470
  • Development of microstructural technology using architecturally complex block copolymer
    Grants-in-Aid for Scientific Research
    01 Apr. 2016 - 31 Mar. 2019
    Satoh Toshifumi
    This study is aiming at establishing new molecular design concept of block copolymer (BCP) materials for next generation lithography.
    Branched and cyclic amphiphilic BCPs as well as tacticity-controlled amphiphilic BCPs were synthesized by using precision polymerization techniques and click reactions. A systematic investigation into those BCPs revealed that the incorporation of branched and cyclic architectures into the BCPs can be an effective mean to reduce the domain-spacing of the microphase-separated structures. Further, the control over the main chain tacticity can be a novel approach to achieve high-quality morphology.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 16H04152
  • Consecutive Cyclization: A Novel Approach for Multicyclic Polymer Synthesis
    Grants-in-Aid for Scientific Research
    01 Apr. 2016 - 31 Mar. 2018
    Satoh Toshifumi
    We here proposed a novel synthetic route toward multicyclic polymers based on the consecutive cyclization of linear polymer precursors possessing a polymerizable group at each chain end. Specifically, the consecutive cyclization was achieved by the cyclopolymerization of macromonomers bearing a norbornenyl group at each chain end, affording multicyclic polymers with the targeted ring size and number of cyclic units. Furthermore, we have performed a systematic investigation of the correlation between the multicyclic architecture and physical properties.
    Japan Society for the Promotion of Science, Grant-in-Aid for Challenging Exploratory Research, Hokkaido University, 16K14000
  • 環状ブロック共重合体を用いた銀ナノ粒子の安定化
    科学研究費助成事業
    09 Nov. 2015 - 31 Mar. 2018
    山本 拓矢, QUINSAAT JOSE ENRICO
    本研究の目的は、環状両親媒性ブロック共重合体を用いた銀ナノ粒子の新奇分散安定化手法の開発である。これまでに当研究グループは、環状高分子から成るミセルが優れた分散安定性を有することを見出した。例えば、対応する直鎖状高分子ミセルと比較すると環状高分子ミセルは40°C差以上の耐熱性および約30倍の耐塩性を示すことを報告している。本提案では、この現象と金属ナノ粒子の表面修飾を組み合わせて、銀ナノ粒子を環状両親媒性ブロック共重合体で修飾することにより高分散安定化を狙う。つまり、上述の環状高分子ミセルは高い高分子密度を有するため、銀ナノ粒子を修飾した場合も同様に高密度の被覆膜を形成することで優れた表面安定性を示すと考えられる。さらに、応用として触媒・医療・光学・電子工学に幅広く用いられる金属ナノ粒子材料の性能向上につながる技術の開拓を目指すものである。
    まず、銀ナノ粒子安定化に適した環状ポリエチレンオキシドや環状のPluronicの合成を行った。これらの親水鎖は、いずれも生体適合性を有するため銀ナノ粒子の表面プラズモン共鳴を利用した医療用バイオセンサーなどに応用可能である。また、銀ナノ粒子の被覆膜厚が物性に与える影響を調査するため、親水・疎水各セグメントの分子量を包括的に検討した。
    さらに、合成した種々の環状ブロック共重合体を銀ナノ粒子の表面修飾に利用し、その安定性を検討し、高分子のトポロジーに由来する安定性の差異を検証した。ここで、過酷な条件下での安定性評価として、NaCl水溶液に対する耐性を測定した。
    日本学術振興会, 特別研究員奨励費, 北海道大学, 15F15763
  • 好熱菌の環状脂質分子を摸倣した高分子の自己組織化による機能材料の開発
    科学研究費助成事業
    01 Apr. 2015 - 31 Mar. 2017
    山本 拓矢
    本研究は、好熱菌と呼ばれる単細胞生物の細胞膜に存在する環状脂質分子を摸倣した合成高分子に自己組織化を誘導し、形成した好熱菌細胞膜モデルを利用して高安定性獲得のメカニズムの解明を行い、その応用を探求するものである。本年度の実績として、昨年度までに作製に成功したベシクルの詳細な構造解析を行い、さらにそのベシクル水溶液をNaCl、HClまたはNaOH存在下、および様々な温度条件下において、光散乱測定および水溶液の光透過性によりベシクルの熱安定性を評価した。加えて、フルオレセインナトリウム塩やローダミン6Gの存在がどの様に構造安定性に影響を与えるかについて評価を行った。
    静的光散乱測定から求めた会合体の分子量から、いずれも中空構造が示唆され、環状高分子から得られたベシクルの会合数が直鎖状高分子のベシクルよりもやや大きいことから、環状高分子はより密な自己組織化構造体を形成していることが示唆された。この結果は、環状高分子から成るミセルが直鎖状高分子から成るミセルと比較して、より密な構造を形成することと合致している。直鎖状および環状ブロック共重合体から得られたベシクルの熱安定性を動的光散乱測定により評価したところ両ベシクルは、純水中ではいずれも80 °Cを超える耐熱性を示す一方、NaClを添加すると、有意に熱安定性が変化した。また、フルオレセインナトリウム塩やローダミン6G、および酸塩基の影響も確認された。これらの結果より、ベシクルに対する高分子トポロジーとゲスト分子および周囲の環境に関する知見が得られた。
    日本学術振興会, 新学術領域研究(研究領域提案型), 北海道大学, 15H01595
  • Applications of topological polymers to soft materials
    Grants-in-Aid for Scientific Research
    01 Apr. 2015 - 31 Mar. 2017
    Yamamoto Takuya, INOUE Joe
    Telechelic poly(ethylene oxide) with anthryl or coumarinyl end groups was synthesized. An aqueous solution of the telechelics was irradiated with UV light at 365nm to form a cyclic polymer product via photodimerization of the anthryl or coumarinyl end groups. Moreover, the cyclic-to-linear reverse topological transformation was conducted by thermal cleavage or photocleavage of the cyclized polymers by heating or irradiation of UV light at 254 nm.
    Moreover, cyclic block copolymers consisting of poly(L- or D-lactide) and poly(ethylene oxide), i.e., PLLA-PEO and PDLA-PEO, respectively, were synthesized from their corresponding linear triblock PLLA-PEO-PLLA and PDLA-PEO-PDLA precursors. Photocleavable cyclic PLLA-PEO and PDLA-PEO block copolymers having an o-nitrobenzyl group were synthesized. A mixture of micellar solutions of these block copolymers formed a gel upon UV irradiation.
    Japan Society for the Promotion of Science, Grant-in-Aid for Challenging Exploratory Research, Hokkaido University, 15K13703
  • Topology Effects of Polymers in Molecular Assemblies
    Grants-in-Aid for Scientific Research
    01 Apr. 2014 - 31 Mar. 2017
    Yamamoto Takuya, INOUE Joe
    Multicyclic polymers are categorized into three basic polymer topologies of fused, spiro and bridged shapes. A double-eight structure that is a novel multicyclic polymer topology with combined two basic structures of spiro and bridged shapes was synthesized. An 8-shaped telechelics having an ethynyl group was synthesized by using the ESA CF process. A click reaction between this telechelics and linear telechelics having azido end groups resulted in the formation of a double-eight polymer. Characterization was performed by 1H NMR, SEC and MALDI TOF MS, The crude product was subjected to the fractionation by means of a preparative SEC technique.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), 26288099
  • Amplification of topology effects of polymers by self-assembly
    Grants-in-Aid for Scientific Research
    01 Apr. 2011 - 31 Mar. 2015
    YAMAMOTO Takuya, TEZUKA Yasuyuki
    Polymeric micelles were prepared from linear poly(methyl acrylate)-b-poly(ethylene oxide)-b-poly(methyl acrylate) and cyclic counterparts. Temperature and salt responses of these micelles were determined by turbidity measurements to disclose that the micelles formed from the cyclic copolymers have higher thermal and salt resistance in comparison with the linear counterparts.
    Cyclic homo polylactides and stereoblock polylactides with head-to-head (HH) and head-to-tail (HT) linking orientations were synthesized. DSC measurements showed that the melting temperature of a cyclic PLLA/cyclic PDLA blend was decreased from that of a relevant linear PLLA/linear PDLA blend. Furthermore, the melting temperature of the HH stereoblock PLA increased whereas that of the relevant HT counterpart decreased upon cyclization.
    Japan Society for the Promotion of Science, Grant-in-Aid for Young Scientists (A), Tokyo Institute of Technology, 23685022
  • Tailored Construction of Novel Multicyclic Polymer Architectures for Breakthrough Properties and Functions
    Grants-in-Aid for Scientific Research
    01 Apr. 2011 - 31 Mar. 2014
    TEZUKA Yasuyuki, YAMAMOTO Takuya
    A novel effective means to construct a variety of novel cyclic and multicyclic polymer topologies, including those possessing beta-, gamma- or delta-graph constructions, were developed based on an electrostatic self-assembly and covalent fixation (ESA-CF) protocol, where polymer self-assemblies comprised of linear or branched telechelic precursors having cyclic ammonium salt groups accompanying pluricarboxylate counteranions were employed as key intermediates. The ESA-CF process was also combined with such effective linking chemistry as metathesis condensation (clip) and alkyne-azide addition (click) reactions to afford complex cyclic and multicyclic polymer architectures. By making use of these precisely designed topological polymers, unusual properties and functions were disclosed based on their cyclic and multicyclic topologies, i.e., topology effects, unattainable either by linear or branched counterparts.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Tokyo Institute of Technology, 23350050
  • 機能性環状高分子ミセルの開発
    科学研究費助成事業
    01 Apr. 2011 - 31 Mar. 2013
    山本 拓矢
    古細菌は環状トポロジーを有する脂質分子を細胞膜に持つことで、高温、高塩濃度などの極限環境に適応していると考えられている。我々は、これに着想を得、両親媒性ブロック共重合体により環状脂質分子を模倣し、ミセルを形成することでトポロジー効果をナノスケールにおいて増幅し、その耐熱性および耐塩性を飛躍的に向上させることに成功した。そこで今回、分子集合体の構築によるトポロジー効果増幅の概念をマクロスケールにまで拡張するために、環状両親媒性ブロック共重合体よりヒドロゲルを構築し、相転移挙動とゲスト分子の放出挙動を調査した。
    先ず、ポリエチレンオキシドと、ポリブチルアクリレートとからなる直鎖状AB型およびABA型両親媒性ブロック共重合体(L-AB, L-ABA)、並びに対応する環状AB型両親媒性ブロック共重合体(C-AB)を合成した。
    続いて、これらの共重合体よりヒドロゲルを作製した。得られたヒドロゲルのゾル-ゲル転移挙動を試験管倒立法により評価したところ、C-ABのゾル-ゲル転移温度は35, 40, 45, 50 wt%の濃度においてそれぞれ25, 35, 40, 45 °Cと測定され、対応するL-ABおよびL-ABAに比べ低い転移温度を持つことが明らかとなった。これは、C-ABが環状構造を有しているため、高分子鎖の絡み合いが抑制されたことが理由として考えられる。
    さらに、水溶性の蛍光分子として知られるFluorescein sodium salt(FSS)をヒドロゲル中に担持し、水中への放出を試みたところ、L-ABおよびL-ABAによるヒドロゲルからは時間経過に伴う明確なFSSの放出が観測された。一方、興味深いことにC-ABによるヒドロゲルからの放出はほとんど見られなかった。すなわち、直鎖状から環状へのトポロジー変換に伴って、ヒドロゲルのゲスト保持能力が大きく向上するという効果が見出された。
    日本学術振興会, 新学術領域研究(研究領域提案型), 東京工業大学, 23106709
  • Formation of a chain-end-free surface on a self-assembled monolayer of a cyclic disulfide
    Grants-in-Aid for Scientific Research
    2009 - 2010
    YAMAMOTO Takuya
    Cyclic alkanedisulfides were synthesized from linear alkanedithiols consisting of 10 and 20 carbon atoms using a bromo-Wang resin. The size of the macrocycles was determined by SEC measurements. While an alkanedithiol consisting of 20 carbon atoms mainly produced monomeric, dimeric, and trimeric macrocycles with a decreasing yield as the increasing size of the macrocycle, that of 10 carbon atoms resulted in the formation of only dimeric and higher macrocycles.
    Japan Society for the Promotion of Science, Grant-in-Aid for Research Activity Start-up, Tokyo Institute of Technology, 21850013
  • Construction of polymer nanostructures based on topological polymer chemistry
    Grants-in-Aid for Scientific Research
    2005 - 2008
    TEZUKA Yasuyuki, ADACHI Kaoru, YAMAMOTO Takuya
    単環状および多環状構造を含む様々な高分子の「かたち(トポロジー)」の設計および合成プロセスの開発を行った.環状アンモニウム塩を末端または主鎖中に導入した直鎖状および分岐状高分子前駆体(テレケリクス)を多官能カルボン酸対アニオンと組み合わせると、静電相互作用によって希釈下で自己組織化イオン性高分子集合体を形成する.さらに環状アンモニウム塩基の開環または脱離反応に基づく共有結合変換プロセスを開発し、多様な単環状・多環状高分子の効率的合成を達成した.また、このプロセスに特徴的なイオン性高分子集合体の動的平衡や、得られる環状テレケリクスの高分子反応を利用することによって、さらに高度な高分子トポロジー設計も実現した.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Tokyo Institute of Technology, 17350054

Industrial Property Rights

  • 修飾金属ナノ粒子及び医薬組成物               
    Patent right, 山本 拓矢, キンサート ホセ エンリコ, 国立大学法人北海道大学
    特願2017-218620, 13 Nov. 2017
    Foreign
    米国出願・出願番号: 16/188509・出願日: 2018/11/13