MF研究者総覧

研究者データベース

詳細
山本　拓矢(ヤマモト　タクヤ)
工学研究院　応用化学部門　分子機能化学分野
准教授
researchmap個人ページ
Last Updated :2024/05/15

基本情報

所属

  • 工学研究院　応用化学部門　分子機能化学分野

職名

  • 准教授

学位

  • Ph.D.（University of Utah）

ホームページURL

科研費研究者番号

  • 30525986

ORCID ID

J-Global ID

研究キーワード

  • 高分子化学   超分子化学   Supramolecular Chemistry   

研究分野

  • ナノテク・材料 / 高分子化学

担当教育組織

職歴

  • 2015年 - 現在 北海道大学 大学院工学研究院 応用化学部門 准教授
  • 2008年 - 2015年 東京工業大学 大学院理工学研究科 有機・高分子物質専攻 助教
  • 2005年 - 2008年 :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年 - 2008年 :Japan Science and Technology Agency ERATO-SORST Aida Nanospace Project Researcher
  • 2008年 -:Tokyo Institute of Technology Department of Organic and Polymeric Materials Assistant Professor
  • 2005年 - 2005年 :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年 - 2005年 :Japan Science and Technology Agency ERATO Aida Nanospace Project Researcher
  • 2004年 - 2005年 :University of Utah Department of Chemistry Postdoctoral Fellow
  • 2004年 - 2005年 :University of Utah Department of Chemistry Postdoctoral Fellow

学歴

  •         - 2004年   University of Utah   Department of Chemistry
  •         - 2004年   University of Utah
  •         - 1999年   University of Utah   College of Science   Department of Chemistry
  •         - 1999年   University of Utah

所属学協会

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

研究活動情報

論文

  • 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 2024年04月
  • Erika Terada, Takuya Isono, Toshifumi Satoh, Takuya Yamamoto, Toyoji Kakuchi, Shin-ichiro Sato
    Chemical Physics Letters 840 141137 - 141137 2024年04月
  • 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
    2024年02月
  • 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 2024年01月 [査読有り]
  • 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 2023年12月
  • Tianle Gao, Feng Li, Ryota Suzuki, Huan Li, Takuya Yamamoto, Xiaochao Xia, Takuya Isono, Toshifumi Satoh
    Macromolecules 2023年10月12日
  • Shunsuke Mizutani, Shunya Kita, Naoya Sakai, Takuya Yamamoto, Andrej Koleżyński, Toyoji Kakuchi, Shin-ichiro Sato
    Macromol 3 3 653 - 664 2023年09月08日 
    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.
  • 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  2023年07月 [査読有り][通常論文]
     
    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.
  • Ebii, Y, Mato, Y, Li, F, Tajima, K, Yamamoto, T, Isono, T, Satoh, T
    Polym. Chem. 14 26 3099 - 3109 2023年06月 [査読有り][通常論文]
     
    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...
  • Erika Terada, Takuya Isono, Toshifumi Satoh, Takuya Yamamoto, Toyoji Kakuchi, Shinichiro Sato
    Nanomaterials 2023年05月12日
  • Satoshi Katsuhara, Naoki Sunagawa, Kiyohiko Igarashi, Yutaka Takeuchi, Kenji Takahashi, Takuya Yamamoto, Feng Li, Kenji Tajima, Takuya Isono, Toshifumi Satoh
    Carbohydrate Polymers 2023年05月
  • 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 2023年01月28日 
    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.
  • Dongyang Li, Wataru Takarada, Minoru Ashizawa, Takuya Yamamoto, Hidetoshi Matsumoto
    Polymer 2023年 
    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.
  • Takuya Isono, Ema Baba, Shunma Tanaka, Ken Miyagi, Takahiro Dazai, Feng Li, Takuya Yamamoto, Kenji Tajima, Toshifumi Satoh
    Polymer Chemistry 14 22 2675 - 2684 2023年 
    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.
  • Yubo Wang, Jose Enrico Quijano Quinsaat, Feng Li, Takuya Isono, Kenji Tajima, Toshifumi Satoh, Shin-ichiro Sato, Takuya Yamamoto
    Polymers 14 21 4535 - 4535 2022年10月26日 [査読有り][通常論文]
     
    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.
  • Tianle Gao, Xiaochao Xia, Kenji Tajima, Takuya Yamamoto, Takuya Isono, Toshifumi Satoh
    Macromolecules 55 21 9373 - 9383 2022年10月21日 [査読有り]
  • 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 2022年09月12日
  • Nishimura, T, Katsuhara, S, Lee, C, Ree, B. J, Borsali, R, Yamamoto, T, Tajima, K, Satoh, T, Isono, T
    Nanomaterials 12 10 1653 - 1653 2022年05月 [査読有り]
     
    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.
  • 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 2022年05月 [査読有り]
  • 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 2022年04月 [査読有り]
     
    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.
  • Ryota Suzuki, Xiaochao Xia, Tianle Gao, Takuya Yamamoto, Kenji Tajima, Takuya Isono, Toshifumi Satoh
    Polymer Chemistry 13 38 5469 - 5477 2022年 
    Hyperbranched polyesters (HBPEs) are well-known interesting materials used in many fields.
  • Yamamoto, T., Masuda, Y., Tezuka, Y., Korchagina, E., Winnik, F.M.
    Langmuir 37 in press  2022年 [査読有り]
  • 勝原哲, 髙木靖子, 砂川直輝, 五十嵐圭日子, 山本拓矢, 田島健次, 磯野拓也, 佐藤敏文
    Cellulose Commun. 28 4 140 - 148 2021年12月
  • Oziri, Onyinyechukwu, Maeki, Masatoshi, Tokeshi, Manabu, Isono, Takuya, Tajima, Kenji, Satoh, Toshifumi, Sato, Shin-ichiro, Yamamoto, Takuya
    Langmuir 2021年12月 [査読有り][招待有り]
  • Saburo Kobayashi, Mayoh Ashiya, Takuya Yamamoto, Kenji Tajima, Yasunori Yamamoto, Takuya Isono, Toshifumi Satoh
    Polymers 13 23 4168 - 4168 2021年11月 [査読有り]
     
    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.
  • 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 2021年11月 [査読有り]
     
    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...
  • Mato, Y, Sudo, M, Marubayashi, H, Ree, B, Tajima, K, Yamamoto, T, Jinnai, H, Isono, T, Satoh, T
    Macromolecules 54 19 9079 - 9090 2021年09月
  • Dongyang Li, Wataru Takarada, Minoru Ashizawa, Takuya Yamamoto, Hidetoshi Matsumoto
    Polymer 123994 - 123994 2021年07月 [査読有り]
  • Katsuhara, S., Takagi, Y., Sunagawa, N., Igarashi, K., Yamamoto, T., Tajima, K., Isono, T., Satoh, T.
    ACS Sustainable Chemistry and Engineering 9 29 2021年06月
  • Kodai Watanabe, Noya Kaizawa, Brian J. Ree, Takuya Yamamoto, Kenji Tajima, Takuya Isono, Toshifumi Satoh
    Angewandte Chemie International Edition 60 33 18122 - 18128 2021年05月26日 [査読有り]
  • 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 2021年05月 [査読有り][通常論文]
  • Taku Sawayama, Yubo Wang, Tomohisa Watanabe, Masayoshi Takayanagi, Takuya Yamamoto, Nobuhiko Hosono, Takashi Uemura
    Angew. Chem. 60 21 11830 - 11834 2021年04月
  • 環状ポリエチレングリコールを用いた金ナノ粒子の分散安定化
    渡邉 智久, 王 钰博, 山本 拓矢
    ナノ学会刊行和文誌 2021年03月 [査読無し][招待有り]
  • 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 2020年12月01日 
    © 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.
  • 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 2020年12月 
    © 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.
  • Yoshinobu Mato, Kohei Honda, Brian J. Ree, Kenji Tajima, Takuya Yamamoto, Tetsuo Deguchi, Takuya Isono, Toshifumi Satoh
    Communications Chemistry 3 1 2020年12月 [査読有り][通常論文]
  • Saburo Kobayashi, Kaiyu Fujiwara, Dai Hua Jiang, Takuya Yamamoto, Kenji Tajima, Yasunori Yamamoto, Takuya Isono, Toshifumi Satoh
    Polymer Chemistry 11 42 6832 - 6839 2020年11月14日 
    © 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.
  • Kaoru Takojima, Hiroshi Makino, Tatsuya Saito, Takuya Yamamoto, Kenji Tajima, Takuya Isono, Toshifumi Satoh
    Polymer Chemistry 11 39 6365 - 6373 2020年10月21日 
    © 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.
  • 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 2020年06月16日 [査読有り][通常論文]
  • Kenta Iwashima, Takuya Yamamoto, Yasuyuki Tezuka, Jiro Kumaki
    Langmuir 36 22 6216 - 6221 2020年06月09日 [査読有り][通常論文]
     
    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.
  • Shin Inagaki, Takuya Yamamoto, Tomoya Higashihara
    Macromolecular Rapid Communications 41 11 2000148 - 2000148 2020年06月 [査読有り][通常論文]
     
    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.
  • 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 2020年02月 [査読有り][通常論文]
     
    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.
  • Kodai Watanabe, Satoshi Katsuhara, Hiroaki Mamiya, Yukihiko Kawamura, Takuya Yamamoto, Kenji Tajima, Takuya Isono, Toshifumi Satoh
    Nanoscale 2020年 [査読有り][通常論文]
     

    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...

  • Satoshi Katsuhara, Hiroaki Mamiya, Takuya Yamamoto, Kenji Tajima, Takuya Isono, Toshifumi Satoh
    Polymer Chemistry 2020年 [査読有り][通常論文]
  • 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 2020年01月01日 [査読有り][通常論文]
     
    © 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.
  • 環状高分子合成の進展と機能材料への可能性
    山本 拓矢
    高分子 68 613 - 617 2019年11月 [査読有り][招待有り]
  • Yoshida, K., Yamamoto, T., Tajima, K., Isono, T., Satoh, T.
    Polymer Chemistry 10 24 3390 - 3398 2019年06月 [査読有り][通常論文]
  • Kyoda, K., Yamamoto, T., Tezuka, Y.
    Journal of the American Chemical Society 141 18 7526 - 7536 2019年05月08日 [査読有り][通常論文]
  • 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 2019年05月06日 [査読有り][通常論文]
  • Kodai Watanabe, Satoshi Katsuhara, Hiroaki Mamiya, Takuya Yamamoto, Kenji Tajima, Takuya Isono, Toshifumi Satoh
    Chemical science 10 11 3330 - 3339 2019年03月21日 [査読有り][通常論文]
     
    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.
  • 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 2019年03月07日 [査読有り][通常論文]
  • Yoshinobu Mato, Kohei Honda, Kenji Tajima, Takuya Yamamoto, Takuya Isono, Toshifumi Satoh
    Chemical science 10 2 440 - 446 2019年01月14日 [査読有り][通常論文]
     
    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.
  • Ree Brian J, Satoh Toshifumi, Yamamoto Takuya
    POLYMERS 11 1 2019年01月 [査読有り][通常論文]
     
    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.
  • Konomoto, T., Nakamura, K., Yamamoto, T., Tezuka, Y.
    Macromolecules 52 23 9208 - 9219 2019年 [査読有り][通常論文]
  • 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 2018年11月27日 [査読有り][通常論文]
  • Yoshida, K., Tanaka, S., Yamamoto, T., Tajima, K., Borsali, R., Isono, T., Satoh, T.
    Macromolecules 51 21 8870 - 8877 2018年11月13日 [査読有り][通常論文]
  • Yamamoto, T.
    Reactive and Functional Polymers 132 43 - 50 2018年11月 [査読有り][通常論文]
  • Yoshida, K., Tian, L., Miyagi, K., Yamazaki, A., Mamiya, H., Yamamoto, T., Tajima, K., Isono, T., Satoh, T.
    Macromolecules 51 20 8064 - 8072 2018年10月23日 [査読有り][通常論文]
  • Tomoki Shingu, Takuya Yamamoto, Kenji Tajima, Takuya Isono, Toshifumi Satoh
    Polymers 10 8 2018年08月06日 [査読有り][通常論文]
     
    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.
  • Takuya Isono, Tetsuya Sasamori, Kohei Honda, Yoshinobu Mato, Takuya Yamamoto, Kenji Tajima, Toshifumi Satoh
    Macromolecules 51 10 3855 - 3864 2018年05月22日 [査読有り][通常論文]
     
    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.
  • Tatsuya Saito, Yusuke Aizawa, Takuya Yamamoto, Kenji Tajima, Takuya Isono, Toshifumi Satoh
    Macromolecules 51 3 689 - 696 2018年02月13日 [査読有り][通常論文]
     
    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.
  • Shundo, A., Yamamoto, T., Tezuka, Y., Tanaka, K.
    Toraibarojisuto/Journal of Japanese Society of Tribologists 63 4 248 - 252 2018年01月01日 [査読無し][通常論文]
     
    © 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年 [査読有り][招待有り]
  • 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 2018年 [査読有り][通常論文]
     
    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.
  • Kenji Tajima, Ryo Kusumoto, Ryota Kose, Hiroyuki Kono, Tokuo Matsushima, Takuya Isono, Takuya Yamamoto, Toshifumi Satoh
    BIOMACROMOLECULES 18 10 3432 - 3438 2017年10月 [査読有り][通常論文]
     
    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.
  • Satoshi Honda, Kaoru Adachi, Takuya Yamamoto, Yasuyuki Tezuka
    MACROMOLECULES 50 14 5323 - 5331 2017年07月 [査読有り][通常論文]
     
    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.
  • Ryoto Tanaka, Kodai Watanabe, Takuya Yamamoto, Kenji Tajima, Takuya Isono, Toshifumi Satoh
    POLYMER CHEMISTRY 8 23 3647 - 3656 2017年06月 [査読有り][通常論文]
     
    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.
  • Atsuomi Shundo, Koichiro Hori, Yasuyuki Tezuka, Takuya Yamamoto, Keiji Tanaka
    LANGMUIR 33 9 2396 - 2401 2017年03月 [査読有り][通常論文]
     
    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.
  • Yusuke Satoh, Hirohiko Matsuno, Takuya Yamamoto, Kenji Tajima, Takuya Isono, Toshifumi Satoh
    MACROMOLECULES 50 1 97 - 106 2017年01月 [査読有り][通常論文]
     
    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.
  • Eisuke Baba, Toshiaki Yatsunami, Yasuyuki Tezuka, Takuya Yamamoto
    LANGMUIR 32 40 10344 - 10349 2016年10月 [査読有り][通常論文]
     
    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.
  • Satoshi Habuchi, Takuya Yamamoto, Yasuyuki Tezuka
    JOVE-JOURNAL OF VISUALIZED EXPERIMENTS 115 2016年09月 [査読有り][通常論文]
     
    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.
  • Akihiro Kimura, Tsukasa Hasegawa, Takuya Yamamoto, Hidetoshi Matsumoto, Yasuyuki Tezuka
    MACROMOLECULES 49 16 5831 - 5840 2016年08月 [査読有り][通常論文]
     
    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.
  • Yoichiro Tomikawa, Takuya Yamamoto, Yasuyuki Tezuka
    MACROMOLECULES 49 11 4076 - 4087 2016年06月 [査読有り][通常論文]
     
    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.
  • Takuya Yamamoto, Kotaro Inoue, Yasuyuki Tezuka
    POLYMER JOURNAL 48 4 391 - 398 2016年04月 [査読有り][通常論文]
     
    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'.
  • Takuya Yamamoto, Sakyo Yagyu, Yasuyuki Tezuka
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 138 11 3904 - 3911 2016年03月 [査読有り][通常論文]
     
    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.
  • Qi Meng, Satoshi Honda, Yasuyuki Tezuka, Takuya Yamamoto, Atsuhiro Fujimori
    JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS 54 4 486 - 498 2016年02月 [査読有り][通常論文]
     
    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.
  • Haruna Wada, Takuya Yamamoto, Yasuyuki Tezuka
    MACROMOLECULES 48 17 6077 - 6086 2015年09月 [査読有り][通常論文]
     
    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.
  • Haruna Wada, Yu Kitazawa, Shigeki Kuroki, Yasuyuki Tezuka, Takuya Yamamoto
    LANGMUIR 31 32 8739 - 8744 2015年08月 [査読有り][通常論文]
     
    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).
  • Hiroyuki Heguri, Takuya Yamamoto, Yasuyuki Tezuka
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 54 30 8688 - 8692 2015年07月 [査読有り][通常論文]
     
    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.
  • Eisuke Baba, Toshiaki Yatsunami, Takuya Yamamoto, Yasuyuki Tezuka
    POLYMER JOURNAL 47 5 408 - 412 2015年05月 [査読有り][通常論文]
  • Takuya Yamamoto, Yasuyuki Tezuka
    SOFT MATTER 11 38 7458 - 7468 2015年 [査読有り][通常論文]
     
    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.
  • Naoto Sugai, Shigeo Asai, Yasuyuki Tezuka, Takuya Yamamoto
    POLYMER CHEMISTRY 6 19 3591 - 3600 2015年 [査読有り][通常論文]
     
    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.
  • Satoshi Habuchi, Susumu Fujiwara, Takuya Yamamoto, Yasuyuki Tezuka
    POLYMER CHEMISTRY 6 22 4109 - 4115 2015年 [査読有り][通常論文]
     
    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.
  • Satoshi Honda, Maito Koga, Masatoshi Tokita, Takuya Yamamoto, Yasuyuki Tezuka
    POLYMER CHEMISTRY 6 22 4167 - 4176 2015年 [査読有り][通常論文]
     
    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.
  • 山本 拓矢
    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 2014年12月 [査読有り][招待有り]
  • Yoichiro Tomikawa, Hiroto Fukata, Yee Song Ko, Takuya Yamamoto, Yasuyuki Tezuka
    MACROMOLECULES 47 23 8214 - 8223 2014年12月 [査読有り][通常論文]
     
    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.
  • 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 2014年08月 [査読有り][通常論文]
     
    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.
  • 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 2014年08月 [査読有り][通常論文]
     
    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.
  • Susumu Fujiwara, Takuya Yamamoto, Yasuyuki Tezuka, Satoshi Habuchi
    REACTIVE & FUNCTIONAL POLYMERS 80 3 - 8 2014年07月 [査読有り][通常論文]
     
    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.
  • Takuya Suzuki, Takuya Yamamoto, Yasuyuki Tezuka
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 136 28 10148 - 10155 2014年07月 [査読有り][通常論文]
     
    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.
  • Kyuyoung Heo, Young Yong Kim, Yu Kitazawa, Mihee Kim, Kyeong Sik Jin, Takuya Yamamoto, Moonhor Ree
    ACS MACRO LETTERS 3 3 233 - 239 2014年03月 [査読有り][通常論文]
     
    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.
  • Yee Song Ko, Takuya Yamamoto, Yasuyuki Tezuka
    MACROMOLECULAR RAPID COMMUNICATIONS 35 4 412 - 416 2014年02月 [査読有り][通常論文]
     
    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.
  • Akihiro Kimura, Susumu Kawauchi, Takuya Yamamoto, Yasuyuki Tezuka
    ORGANIC & BIOMOLECULAR CHEMISTRY 12 34 6717 - 6724 2014年 [査読有り][通常論文]
     
    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.
  • Masahito Igari, Hiroyuki Heguri, Takuya Yamamoto, Yasuyuki Tezuka
    MACROMOLECULES 46 18 7303 - 7315 2013年09月 [査読有り][通常論文]
     
    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.
  • Satoshi Habuchi, Susumu Fujiwara, Takuya Yamamoto, Martin Vacha, Yasuyuki Tezuka
    ANALYTICAL CHEMISTRY 85 15 7369 - 7376 2013年08月 [査読有り][通常論文]
     
    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.
  • Takuya Yamamoto
    POLYMER JOURNAL 45 7 711 - 717 2013年07月 [査読有り][通常論文]
     
    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.
  • Fumiya Hatakeyama, Takuya Yamamoto, Yasuyuki Tezuka
    ACS MACRO LETTERS 2 5 427 - 431 2013年05月 [査読有り][通常論文]
     
    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.
  • Kimura Akihiro, Yamamoto Takuya, Tezuka Yasuyuki, Kawauchi Susumu
    ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 245 2013年04月07日 [査読有り][通常論文]
  • Akihiro Kimura, Shinnosuke Takahashi, Susumu Kawauchi, Takuya Yamamoto, Yasuyuki Tezuka
    JOURNAL OF ORGANIC CHEMISTRY 78 7 3086 - 3094 2013年04月 [査読有り][通常論文]
     
    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.
  • Habuchi Satoshi, Fujiwara Susumu, Yamamoto Takuya, Vacha Martin, Tezuka Yasuyuki
    Abstracts of Papers of the American Chemical Society 245 2013年 [査読有り][通常論文]
  • 山本 拓矢
    表面 51 6 297 - 306 広信社 2013年 [査読無し][招待有り]
  • Milan M. Stamenovic, Pieter Espeel, Eisuke Baba, Takuya Yamamoto, Yasuyuki Tezuka, Filip E. Du Prez
    POLYMER CHEMISTRY 4 1 184 - 193 2013年 [査読有り][通常論文]
     
    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.
  • Satoshi Honda, Takuya Yamamoto, Yasuyuki Tezuka
    Nature Communications 4 2013年 [査読有り][通常論文]
     
    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.
  • Yukihiro Tada, Takuya Yamamoto, Yasuyuki Tezuka, Tadashi Kawamoto, Takehiko Mori
    CHEMISTRY LETTERS 41 12 1678 - 1680 2012年12月 [査読有り][通常論文]
     
    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.
  • Naoto Sugai, Takuya Yamamoto, Yasuyuki Tezuka
    ACS MACRO LETTERS 1 7 902 - 906 2012年07月 [査読有り][通常論文]
     
    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.
  • Eisuke Baba, Takuya Yamamoto
    Topological Polymer Chemistry: Progress of Cyclic Polymers in Syntheses, Properties, and Functions 329 - 348 2012年01月01日 [査読有り][通常論文]
     
    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.
  • Eisuke Baba, Satoshi Honda, Takuya Yamamoto, Yasuyuki Tezuka
    POLYMER CHEMISTRY 3 7 1903 - 1909 2012年 [査読有り][通常論文]
     
    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).
  • Naoto Sugai, Hiroyuki Heguri, Takuya Yamamoto, Yasuyuki Tezuka
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 133 49 19694 - 19697 2011年12月 [査読有り][通常論文]
     
    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.
  • Takuya Yamamoto, Yasuyuki Tezuka
    Complex Macromolecular Architectures: Synthesis, Characterization, and Self-Assembly 1 - 19 2011年05月03日 [査読有り][通常論文]
     
    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.
  • Takuya Yamamoto, Yasuyuki Tezuka
    EUROPEAN POLYMER JOURNAL 47 4 535 - 541 2011年04月 [査読有り][通常論文]
     
    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.
  • Takuya Yamamoto, Yasuyuki Tezuka
    POLYMER CHEMISTRY 2 9 1930 - 1941 2011年 [査読有り][通常論文]
     
    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.
  • Takuya Yamamoto
    KOBUNSHI RONBUNSHU 68 8 550 - 561 2011年 [査読有り][通常論文]
     
    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.
  • Takuya Yamamoto, Yasuyuki Tezuka
    KOBUNSHI RONBUNSHU 68 12 782 - 794 2011年 [査読有り][通常論文]
     
    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.
  • Naoto Sugai, Hiroyuki Heguri, Kengo Ohta, Qingyuan Meng, Takuya Yamamoto, Yasuyuki Tezuka
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 132 42 14790 - 14802 2010年10月 [査読有り][通常論文]
     
    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.
  • Kazuyuki Ishikawa, Takuya Yamamoto, Hiroyuki Harada, Yasuyuki Tezuka
    MACROMOLECULES 43 17 7062 - 7067 2010年09月 [査読有り][通常論文]
     
    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.
  • Satoshi Honda, Takuya Yamamoto, Yasuyuki Tezuka
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 132 30 10251 - 10253 2010年08月 [査読無し][通常論文]
     
    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.
  • Takuya Yamamoto, Satoshi Honda, Yasuyuki Tezuka
    Polym. Prepr. 51 365 - 366 2010年 [査読有り][通常論文]
  • 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
    山本 拓矢
    化学 65 70 - 71 2010年 [査読無し][招待有り]
  • Kazuyuki Ishikawa, Takuya Yamamoto, Masumi Asakawa, Yasuyuki Tezuka
    MACROMOLECULES 43 1 168 - 176 2010年01月 [査読無し][通常論文]
     
    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.
  • Satoshi Habuchi, Norihiro Satoh, Takuya Yamamoto, Yasuyuki Tezuka, Martin Vacha
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 49 8 1418 - 1421 2010年 [査読無し][通常論文]
  • 山本拓矢
    有機合成化学協会誌 67 9 947 - 948 2009年09月 [査読有り][招待有り]
     
    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.
  • 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 2008年06月 [査読無し][通常論文]
     
    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.
  • Justin L Mynar, Takuya Yamamoto, Atsuko Kosaka, Takanori Fukushima, Noriyuki Ishii, Takuzo Aida
    Journal of the American Chemical Society 130 5 1530 - 1 2008年02月06日 [査読無し][通常論文]
  • Takuya Yamamoto, Takanori Fukushima, Takuzo Aida
    Advances in Polymer Science 220 1 - 27 2008年 [査読無し][通常論文]
     
    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.
  • 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年 [査読無し][通常論文]
  • Takuya Yamamoto, Takanori Fukushima, Takuzo Aida
    SELF-ASSEMBLED NANOMATERIALS II: NANOTUBES 220 1 - 27 2008年 [査読有り][通常論文]
     
    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.
  • Takuya Yamamoto, Takanori Fukushima, Yohei Yamamoto, Atsuko Kosaka, Wusong Jin, Noriyuki Ishii, Takuzo Aida
    Journal of the American Chemical Society 128 44 14337 - 40 2006年11月08日 [査読無し][通常論文]
     
    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.
  • Takuya Yamamoto, Takanori Fukushima, Wusona Jin, Yuki Suna, Norivuki Ishii, Takuzo Aida
    Polymer Preprints, Japan 55 1 260  2006年 [査読有り][通常論文]
     
    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.
  • M Schweiger, T Yamamoto, PJ Stang, D Blaser, R Boese
    JOURNAL OF ORGANIC CHEMISTRY 70 12 4861 - 4864 2005年06月 [査読無し][通常論文]
     
    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.
  • C Addicott, Oesterling, I, T Yamamoto, K Mullen, PJ Stang
    JOURNAL OF ORGANIC CHEMISTRY 70 3 797 - 801 2005年02月 [査読無し][通常論文]
     
    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.
  • 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 2004年09月 [査読無し][通常論文]
     
    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.
  • T Yamamoto, AM Arif, PJ Stang
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 125 40 12309 - 12317 2003年10月 [査読無し][通常論文]
     
    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.
  • CJ Kuehl, T Yamamoto, Seidel, SR, PJ Stang
    ORGANIC LETTERS 4 6 913 - 915 2002年03月 [査読無し][通常論文]
     
    [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.

書籍

  • 基礎高分子科学第2版
    山本 拓矢 (担当:分担執筆)
    東京化学同人 2020年01月
  • 環状高分子の合成と機能発現
    山本 拓矢 (担当:分担執筆範囲: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年
  • ナノテクノロジーが拓く未来の医療
    山本 拓矢 (担当:分担執筆範囲: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年
  • 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 (担当:分担執筆範囲:トポロジカル高分子の合成)
    シーエムシー出版 2014年
  • Baba, E, Yamamoto, T (範囲:Self-Assembly and Functions of Cyclic Polymers)
    World Scientific 2013年 (ISBN: 9789814401272)
  • Yamamoto, T, Tezuka, Y (担当:共著範囲:Multicyclic Polymers)
    Wiley-VCH 2012年 (ISBN: 9783527327577)
  • Yamamoto, T, Tezuka, Y (担当:分担執筆範囲:Cyclic and Multicyclic Topological Polymers)
    John Wiley & Sons 2011年 (ISBN: 9780470825136)
  • 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 (担当:分担執筆範囲: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年

講演・口頭発表等

  • Cyclic Polymers Synthesis and Characterization  [招待講演]
    山本 拓矢
    The Second International Conference of Polymeric and Organic Materials in Yamagata University 2019年12月 口頭発表（招待・特別）
  • Cyclic Polymer Synthesis and Their Unique Characteristics  [招待講演]
    山本 拓矢
    2019年11月 公開講演，セミナー，チュートリアル，講習，講義等 POSTECH
  • Synthesis of Cyclic Polymers and Their Unique Properties  [招待講演]
    山本 拓矢
    Korea–Japan Joint Polymer Symposium on Polymer Science 2019 2019年09月 口頭発表（招待・特別）
  • Advanced Synthesis of Cyclic Polymers and Their Unique Characteristics  [招待講演]
    山本 拓矢
    Polymers and Networks via Topology and Entanglement 2019年08月 口頭発表（招待・特別）
  • 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  [招待講演]
    山本 拓矢
    次世代物質探索のための離散幾何学 研究成果発表会 2019年08月 口頭発表（招待・特別）
  • Synthesis and Unique Properties of Cyclic Polymers  [招待講演]
    山本 拓矢
    2nd Asian–French Workshop on Polymer Science 2019年07月 口頭発表（招待・特別）
  • Synthesis and Properties of Defect-Free Cyclic P3HT  [招待講演]
    山本 拓矢
    National Central University–Hokkaido University Joint Symposium 2019年06月 口頭発表（招待・特別）
  • Novel Synthesis and Unique Characteristics of Cyclic Polymers  [招待講演]
    山本 拓矢
    Polymers Meet Topology 2019年02月 口頭発表（招待・特別）
  • 環状高分子を利用した新奇刺激応答型DDS材料の開発  [招待講演]
    山本 拓矢
    「産業基盤の創生」成果報告会（臨時） 2018年10月 その他 キヤノングローバル戦略研究所, 東京
  • 環状高分子を利用した界面制御  [招待講演]
    山本 拓矢
    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」 2018年09月 口頭発表（招待・特別） つくば国際会議場, つくば
  • Synthesis and Self-Assembly of Cyclic Polymers and Structural Analysis of the Molecular Aggregates  [招待講演]
    山本 拓矢
    7th Synchrotron Radiation in Polymer Science 2018年09月 口頭発表（招待・特別） Hwabaek International Convention Center, Gyeongju, Korea
  • Functional Materials Formed from Cyclic Polymers  [招待講演]
    山本 拓矢
    Japan–Korea Joint Polymer Symposium on Polymer Science 2018 2018年07月 口頭発表（招待・特別） Hokkaido University, Sapporo, Japan
  • Synthesis of Cyclic Polymers and Control of Their Properties  [招待講演]
    山本 拓矢
    255th ACS National Meeting 2018年03月 口頭発表（招待・特別） New Orleans, U.S.A.
  • 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  [招待講演]
    山本 拓矢
    第68回コロイドおよび界面化学討論会 2017年09月 口頭発表（招待・特別） 神戸大学, 神戸
  • 環状高分子を使用した機能材料開発  [招待講演]
    山本 拓矢
    第161回東海高分子研究会講演会（夏期合宿） 2017年09月 口頭発表（招待・特別） 西浦温泉ホテルたつき, 蒲郡
  • Development of Functional Materials by Cyclic Polymers  [招待講演]
    山本 拓矢
    International Symposium on Advanced Polymeric Materials 2017 2017年08月 口頭発表（招待・特別） New Huayuan Hotel, Changchun, China
  • Topology for Polymeric Materials  [招待講演]
    山本 拓矢
    Knots and Polymers: Aspects of Topological Entanglement in DNA, Proteins and Graph-shaped Polymers 2017年08月 口頭発表（招待・特別） Ochanomizu University, Tokyo, Japan
  • Self-Assembly and Topological Conversion of Cyclic Polymers  [招待講演]
    山本 拓矢
    Invited Lecture 2016年10月 口頭発表（招待・特別） Donghua University, Shanghai, China
  • Reversible Linear–Cyclic Topological Conversion of Telechelic Polymers by Photo- and Thermal Reactions  [招待講演]
    山本 拓矢
    Symposium of Cyclic Polymer 2016年10月 口頭発表（招待・特別） Soochow University, Suzhou, China
  • Reversible Topological Transformation to Form Cyclic Polymers by Heat- and Light-Triggered Reactions  [招待講演]
    山本 拓矢
    Taiwan–Japan Bilateral Polymer Symposium 2016 2016年09月 口頭発表（招待・特別） National Tsing Hua University, Hsinchu, Taiwan
  • 環状高分子の合成と機能の創出  [招待講演]
    山本 拓矢
    31st Summer University in Hokkaido 2016年09月 口頭発表（招待・特別） 定山渓ビューホテル, 札幌
  • 環状高分子の集積に基づいた機能材料開発  [招待講演]
    山本 拓矢
    伸長プロセス専門委員会 2016年08月 口頭発表（招待・特別） JSW, 室蘭
  • Self-assembly and Topological Transformation of Cyclic Polymers  [招待講演]
    山本 拓矢
    International Workshop on Topology and Graphs in Polymer Chemistry 2016年08月 口頭発表（招待・特別） Tokyo Institute of Technology, Tokyo, Japan
  • Functional Materials by Self-Assembly of Cyclic Polymers  [招待講演]
    山本 拓矢
    HU-NTU-CERMAV Joint Symposium on Functional Materials 2016年08月 口頭発表（招待・特別） Hokkaido University, Sapporo, Japan
  • 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  [招待講演]
    山本 拓矢
    生物規範工学 公開講演会 2016年08月 口頭発表（招待・特別） 北海道大学, 札幌
  • 環状両親媒性ブロック共重合体によるベシクルの構築  [招待講演]
    山本 拓矢
    精密ネットワークポリマー研究会 2016年07月 口頭発表（招待・特別） 東京工業大学, 東京
  • 環状高分子の自己組織化と機能発現  [招待講演]
    山本 拓矢
    第65回高分子学会年次大会 2016年05月 口頭発表（招待・特別） 神戸国際会議場・展示場, 神戸
  • Topological Transformation and Self-Assembly of Cyclic Polymers  [招待講演]
    山本 拓矢
    Japan–Korea Joint Symposium 2015 2015年10月 口頭発表（招待・特別） Kitakyushu International Conference Center, Kitakyushu, Japan
  • 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  [招待講演]
    山本 拓矢
    関東高分子若手研究会 サマーキャンプ2015 2015年08月 口頭発表（招待・特別） 東京農工大学合宿宿泊施設館山荘, 館山
  • Emerging Functionalities of Cyclic Polymers  [招待講演]
    山本 拓矢
    Invited Lecture 2015年03月 口頭発表（招待・特別） ETH Zürich, Zürich, Switzerland
  • Synthesis and Self-Assembly of Cyclic Polymers toward the Amplification of Topology Effects  [招待講演]
    山本 拓矢
    Taiwan–Japan Bilateral Polymer Symposium-2014 2014年11月 口頭発表（招待・特別） National Cheng Kung University, Tainan, Taiwan
  • Synthesis and Self-Assembly of Cyclic Polymers toward the Amplification of Topology Effects  [招待講演]
    山本 拓矢
    Taiwan–Japan Bilateral Polymer Symposium-2014 2014年11月 口頭発表（招待・特別） National Cheng Kung University, Tainan, Taiwan
  • 環状ポリ乳酸を利用した機能材料の開発  [招待講演]
    山本 拓矢
    第15回リング・チューブ超分子研究会シンポジウム 2014年10月 口頭発表（招待・特別） 東京工業大学, 東京
  • 自己組織化による分子集合体の形成と機能発現  [招待講演]
    山本 拓矢
    環状高分子が示すトポロジー効果の増幅 2014年10月 口頭発表（招待・特別） 奈良先端科学技術大学院大学, 生駒
  • 環状トポロジーを利用した高分子機能材料の開発  [招待講演]
    山本 拓矢
    ISCセミナー 2014年06月 口頭発表（招待・特別） 産業技術総合研究所, つくば
  • 環状高分子が発現する機能特性の探求  [招待講演]
    山本 拓矢
    ソフトインターフェースの分子科学 第10回領域会議 2014年03月 口頭発表（招待・特別） みのお山荘風の杜, 箕面
  • Cyclized Amphiphilic Block Copolymers toward Controlled Release  [招待講演]
    山本 拓矢
    BIT’s 3rd Annual Symposium of Drug Delivery Systems 2013年11月 口頭発表（招待・特別） Hainan International Convention and Exhibition Center, Haikou, China
  • 環状高分子を利用した機能材料の創製  [招待講演]
    山本 拓矢
    第80回高分子若手研究会［関西］ 2013年07月 口頭発表（招待・特別） 関西セミナーハウス, 京都
  • 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  [招待講演]
    山本 拓矢
    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 2013年07月 口頭発表（招待・特別） 兵庫県民会館
  • 環状高分子の自己組織化による機能発現  [招待講演]
    山本 拓矢
    日本化学会第93春季年会（2013） 若い世代の特別講演会 2013年03月 口頭発表（招待・特別） 立命館大学, 草津
  • 環状高分子を利用したソフトマテリアルの創製  [招待講演]
    山本 拓矢
    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 2013年01月 口頭発表（招待・特別） タワーホール船堀, 東京
  • 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  [招待講演]
    山本 拓矢
    ソフトインターフェースの分子科学 第8回領域会議 2012年07月 口頭発表（招待・特別） 伝国の杜・置賜文化ホール, 米沢
  • Self-Assembly of Cyclic Amphiphilic Block Copolymers and Development of Functions  [招待講演]
    山本 拓矢
    Invited Lecture 2012年07月 口頭発表（招待・特別） The University of Manchester, Manchester, U.K.
  • Formation of a Micelle from an Amphiphilic Cyclic Block Copolymer and Determination of the Stability  [招待講演]
    山本 拓矢
    MacroGroup UK International Conference on Polymer Synthesis & UKPCF International Conference on Polymer Colloids 2012年07月 口頭発表（招待・特別） University of Warwick, Warwick, U.K.
  • Self-Assembly of Cyclic Amphiphilic Block Copolymers and Development of Functions  [招待講演]
    山本 拓矢
    Invited Lecture 2012年07月 口頭発表（招待・特別） Ghent University, Ghent, Belgium
  • 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  [招待講演]
    山本 拓矢
    九州地区高分子若手研究会・夏の講演会 2012年06月 口頭発表（招待・特別） ホテルクラウンパレス小倉, 小倉
  • 自己組織化によるナノ構造体の構築と機能発現  [招待講演]
    山本 拓矢
    分子ロボティクス研究会 2月定例研究会 2012年02月 口頭発表（招待・特別） 東京工業大学, 東京
  • 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  [招待講演]
    山本 拓矢
    トクヤマ科学技術振興財団 第14回研究成果報告会 2011年12月 口頭発表（招待・特別） トクヤマつくば研究所, つくば
  • 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  [招待講演]
    山本 拓矢
    平成23年度東工大挑戦的研究賞授賞式 2011年10月 口頭発表（招待・特別） 東京工業大学, 東京
  • 機能性環状高分子ミセルの開発  [招待講演]
    山本 拓矢
    ソフトインターフェースの分子科学 第6回領域会議 2011年07月 口頭発表（招待・特別） 九州大学, 春日
  • Micelle from a Cyclic Block Copolymer: Stabilization via the "Topology Effect"  [招待講演]
    山本 拓矢
    IPCG Polymer Colloids Conference 2011 2011年06月 口頭発表（招待・特別） University of New Hampshire, Durham, U.S.A.
  • 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  [招待講演]
    山本 拓矢
    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 2010年03月 口頭発表（招待・特別） 東京工業大学, 東京
  • Thermostable Micelle by Self-Assembly of a Cyclized Block Copolymer  [招待講演]
    山本 拓矢
    Korea-Japan Young Scientist Symposium 2010年03月 口頭発表（招待・特別） KAIST, Daejeon, Korea
  • Construction of Topological Block Copolymers through Click Chemistry  [通常講演]
    Advanced Polymeric Materials and Technology symposium 2010年 ポスター発表
  • 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  [通常講演]
    関東高分子若手研究会 2010年
  • Construction of a Thermostable Micelle by Self-Assembly of a Cyclized Polymer  [通常講演]
    239th American Chemical Society National Meeting & Exposition 2010年
  • 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  [通常講演]
    日本化学会第90回春季年会 2010年
  • 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  [通常講演]
    日本化学会第90春年会 2010年
  • 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  [通常講演]
    日本化学会 第90春季年会 2010年 ポスター発表
  • 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  [通常講演]
    日本化学会第90春季年会 (2010) 2010年
  • 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  [通常講演]
    第59回高分子年次大会 2010年
  • 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  [通常講演]
    第59回高分子学会年次大会 2010年
  • 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  [通常講演]
    第59回 高分子学会年次大会 2010年
  • Construction of Topological Block Copolymers through Click Chemistry  [通常講演]
    Advanced Polymeric Materials and Technology symposium 2010年 ポスター発表
  • Construction of a Thermostable Micelle by Self-Assembly of a Cyclized Polymer  [通常講演]
    239th American Chemical Society National Meeting & Exposition 2010年
  • Preparation of self-assembled monolayers (SAMs) from cyclic alkanedisulfides  [通常講演]
    2010年 ポスター発表
  • Construction of a thermostable micelle by a cyclized amphiphilic block copolymer  [通常講演]
    The 90th Annual Meeting of The Chemical 2010年
  • Formation of a Thermostable Polymeric Micelle from a Cyclized Block Copolymer  [通常講演]
    59th SPSJ Annual Meeting 2010年
  • 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  [通常講演]
    2009年
  • Synthesis of Topological Block Copolymers via Click Chemistry  [通常講演]
    ADVANCED FUNCTIONAL MATERIALS CONFERENCE 2009年 ポスター発表
  • 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  [通常講演]
    日本化学会第89春年会 2009年
  • Catenane Synthesis Via Cyclization of a Cyclic Polymer Through Hydrogen-Bonding/Electrostatic Self-Assembly  [通常講演]
    2009 Taiwan-Japan Bilateral Polymer Symposium 2009年
  • 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  [通常講演]
    第58回 高分子学会年次大会 2009年 ポスター発表
  • 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  [通常講演]
    第58回 高分子学会年次大会 2009年 ポスター発表
  • 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  [通常講演]
    第58回高分子学会年次大会 2009年 ポスター発表
  • 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-  [通常講演]
    第58回 高分子学会討論会 2009年
  • 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  [通常講演]
    第58回高分子討論会 2009年
  • Synthesis of a Hetero-Type 2-Catenane via the Cyclization of a Telechelic Polymer Having Hydrogen-Bonding Unit  [通常講演]
    Asia Nanotech Camp 2009 2009年
  • 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  [通常講演]
    第58回 高分子討論会 2009年 ポスター発表
  • 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  [通常講演]
    第58回高分子討論会 2009年 ポスター発表
  • 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  [通常講演]
    第58回高分子討論会 2009年 ポスター発表
  • Formation of a Catenane via the Cyclization of a Telechelic Polymer Having a Hydrogen-Bonding Unit  [通常講演]
    The chemical society of Japan, The 89th Annual Meeting 2009年
  • Synthesis of Topological Block Copolymers via Click Chemistry  [通常講演]
    ADVANCED FUNCTIONAL MATERIALS CONFERENCE 2009年 ポスター発表
  • Catenane Synthesis Via Cyclization of a Cyclic Polymer Through Hydrogen-Bonding/Electrostatic Self-Assembly  [通常講演]
    2009 Taiwan-Japan Bilateral Polymer Symposium 2009年
  • Synthesis and micelle formation of amphiphilic cyclic block copolymers  [通常講演]
    2009年 ポスター発表
  • Synthesis of a Dissymmetric 2-Catenane via the Cyclization of a Telechelic Polymer in the Presence of a Cyclic Polymer Having Hydrogen-Bondings  [通常講演]
    The Society Polymer Science, Japan, Annual Meeting 2009年 ポスター発表
  • Construction of Thermally Stable Micelles by Amphiphilic Cyclic Block Copolymers-Creation of New Topology Effects-  [通常講演]
    Polymer Preprints 2009年
  • Synthesis of a Hetero-Type 2-Catenane via the Cyclization of a Telechelic Polymer Having Hydrogen-Bonding Unit  [通常講演]
    Asia Nanotech Camp 2009 2009年
  • Synthesis of a Hetro-Type 2-Catenane via the Cyclization of a Telechelic Polymer Having Hydrogen-Bonding Unit  [通常講演]
    The Society Polymer science, Japan, Symposium on Macromolecules 2009年 ポスター発表
  • 自己組織化による超分子ナノ構造体の構築  [通常講演]
    山本 拓矢
    第13 回 有機・高分子物質フォーラム 2008年12月 口頭発表（招待・特別） 東京工業大学, 東京
  • 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  [通常講演]
    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年 ポスター発表
  • Formation of One-Handed Nanocoils by Coassembly of Hexabenzocoronene Derivatives  [通常講演]
    International Symposium on Engineering Micro-/Nano-Materials based on Self-Assembling and Self-Organization (ISEM 2008) 2008年 ポスター発表
  • 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  [通常講演]
    日本化学会第88春季年会 2008年
  • 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  [通常講演]
    第57回高分子学会年次大会 2008年 ポスター発表
  • 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  [通常講演]
    第57回高分子学会年次大会 2008年
  • Formation of One-Handed Nanocoils by Self-Assembly of Norbornene-Appended Hexabenzocoronene Derivatives  [通常講演]
    Yamada Conference 2008 2008年 ポスター発表
  • Formation of a Catenane via the Cyclization of a Telechelic Polymer in the Presence of a Cyclic Polymer through Hydrogen-Bonding  [通常講演]
    Tokyo Tech-Asia Materials Week 2008年
  • Formation of One-Handed Nanocoils by Coassembly of Hexabenzocoronene Derivatives  [通常講演]
    International Symposium on Engineering Micro-/Nano-Materials based on Self-Assembling and Self-Organization (ISEM 2008) 2008年 ポスター発表
  • Formation of One-Handed Nanocoils by Self-Assembly of Norbornene-Appended Hexabenzocoronene Derivatives  [通常講演]
    Yamada Conference 2008 2008年 ポスター発表
  • Formation of a Catenane via the Cyclization of a Telechelic Polymer in the Presence of a Cyclic Polymer through Hydrogen-Bonding  [通常講演]
    Tokyo Tech-Asia Materials Week 2008年
  • Formation of Nanocoils and Nanotubes via the Self-Assembly of Norbornene-Appended Amphiphilic Hexabenzocoronene Derivatives  [通常講演]
    6th Nanoarchitectonics Workshop 2007 "One-Dimensional Nanostructures for Nanoarchitectonics" (ODNN 2007) 2007年 ポスター発表
  • 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  [通常講演]
    日本化学会第87春季年会 2007年
  • 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  [通常講演]
    第56回高分子学会年次大会 2007年
  • Helical Nanoarchitectures by Programmed Self-Assembly of Norbornene-Appended Hexabenzocoronene Derivatives  [通常講演]
    Chirality at the Nanoscale 2007年
  • 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  [通常講演]
    第37回構造有機化学討論会 2007年 ポスター発表
  • Formation of Nanocoils and Nanotubes via the Self-Assembly of Norbornene-Appended Amphiphilic Hexabenzocoronene Derivatives  [通常講演]
    6th Nanoarchitectonics Workshop 2007 "One-Dimensional Nanostructures for Nanoarchitectonics" (ODNN 2007) 2007年 ポスター発表
  • Helical Nanoarchitectures by Programmed Self-Assembly of Norbornene-Appended Hexabenzocoronene Derivatives  [通常講演]
    Chirality at the Nanoscale 2007年
  • Programmed Self-Assembly toward New -Electronic Nanoarchitectures  [招待講演]
    山本 拓矢
    Invited Lecture 2006年06月 口頭発表（招待・特別） Tokyo Institute of Technology, Tokyo
  • 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  [通常講演]
    日本化学会第86春季年会 2006年
  • Programmed Self-Assembly toward New π-Electronic Nanostructures  [通常講演]
    2006年
  • 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  [通常講演]
    第55回高分子学会年次大会 2006年
  • 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  [通常講演]
    第55回高分子討論会 2006年
  • Programmed Self-Assembly toward New π-Electronic Nanostructures  [通常講演]
    2006年
  • Equilibrium of a Supramolecular Dimer and Trimer and Determination of Its Thermodynamic Constants  [通常講演]
    226th ACS National Meeting 2003年 ポスター発表
  • Equilibrium of a Supramolecular Dimer and Trimer and Determination of Its Thermodynamic Constants  [通常講演]
    226th ACS National Meeting 2003年 ポスター発表
  • Self-Assembly of Nanoscale Truncated Tetrahedra by Coordination Chemistry  [通常講演]
    37th National Organic Symposium 2001年 ポスター発表
  • Self-Assembly of Nanoscale Truncated Tetrahedra by Coordination Chemistry  [通常講演]
    37th National Organic Symposium 2001年 ポスター発表

その他活動・業績

特許

  • 特願2017-218620:修飾金属ナノ粒子及び医薬組成物  2017年11月13日
    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  
    米国出願・出願番号: 16/188509・出願日: 2018/11/13

受賞

  • 2017年09月 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 
    受賞者: 山本 拓矢
  • 2014年02月 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 
    受賞者: 山本 拓矢
  • 2013年07月 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 
    受賞者: 山本 拓矢
  • 2013年04月 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 
    受賞者: 山本 拓矢
  • 2013年03月 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 
    受賞者: 山本 拓矢
  • 2011年08月 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 
    受賞者: 山本 拓矢
  • 2011年05月 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 
    受賞者: 山本 拓矢
  • 2010年10月 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 
    受賞者: 山本 拓矢
  • 2007年05月 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 
    受賞者: 山本 拓矢
  • 1999年04月 University of Utah Award for Outstanding Performance on the Senior Comprehensive Exam
     
    受賞者: 山本 拓矢

共同研究・競争的資金等の研究課題

  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2023年04月 -2027年03月 
    代表者 : 松本 英俊, 山本 拓矢, 宝田 亘
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2019年04月 -2022年03月 
    代表者 : 佐藤 敏文, 山本 拓矢, 磯野 拓也
     
    本研究は、ブロック共重合体（BCP）が形成するミクロ相分離構造の周期間隔を5nm程度に制御する新規方法論の確立を目指すものである。これを達成する方法論として本研究では主に、１）BCPへの分子内架橋の導入による高分子鎖の広がりの抑制ならびに２）BCPへの大環状ユニットの導入を検討した。その結果、１）の方法論では分子内架橋の導入により、対応する線状BCPと比較して47%の周期間隔縮小に成功し、２）の方法論では最大76%もの周期間隔縮小に成功した。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2019年06月 -2021年03月 
    代表者 : 佐藤 敏文, 山本 拓矢, 磯野 拓也
     
    本研究では、すべてのフレームがソフトな合成高分子からなるカゴ状構造体の簡便合成法開発および物性評価に成功した。具体的には、モデル高分子としてポリカプロラクトン (PCL) からなるカゴ状構造体を精密合成でき、これは通常の直鎖状高分子とは異なり、溶液中でフォールディングした形状をとることが明らかとなった。さらに、カゴ状ユニットが一分子内に高密度に連なった構造体 (カゴ状グラフトPCL) の合成および物性評価も達成した。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2018年04月 -2020年03月 
    代表者 : 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：科学研究費助成事業
    研究期間 : 2016年04月 -2019年03月 
    代表者 : 佐藤 敏文, 山本 拓矢, 磯野 拓也
     
    本研究は、次世代リソグラフィーへの応用に向けたブロック共重合体(BCP)の新規設計指針の確立を目指すものである。 各種の精密リビング重合やクリック反応を駆使することで、分岐状あるいは環状構造を有する両親媒性BCPならびに立体規則性を制御した両親媒性BCPを合成した。ミクロ相分離構造の解析結果より、ブロック共重合体への非直鎖状構造の導入は重合度に依存せずにミクロ相分離構造の周期間隔を微細化する有用な手段となることを明らかにした。また、ブロック共重合体の立体規則性の制御はより高度に配列したモルフォロジーを構築する方法論となり得ることも見出した。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2016年04月 -2018年03月 
    代表者 : 佐藤 敏文, 山本 拓矢, 磯野 拓也
     
    本研究では、多環状高分子の新たな合成法として「連鎖的環形成」を確立した。すなわち、両末端に重合性官能基を備えた直鎖状高分子を前駆体とし、その重合性基を介して次々に環状ユニットを形成するものである。具体的には、両末端にノルボルネニル基を有する直鎖状ポリマーを環化重合することで連鎖的環形成を実現し、環サイズおよび環状ユニット数を制御した多環状高分子の合成に成功した。さらに、本手法により合成したサンプルを用いて多環状高分子の系統的な物性評価も行った。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2015年11月 -2018年03月 
    代表者 : 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：科学研究費助成事業
    研究期間 : 2015年04月 -2017年03月 
    代表者 : 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：科学研究費助成事業
    研究期間 : 2015年04月 -2017年03月 
    代表者 : 山本 拓矢, 井上 浄, 手塚 育志
     
    本研究ではトポロジー変換という高分子の「かたち」に立脚した新たな刺激応答性分子システムの開発を検討するため光開裂性部位を含む環状高分子の合成および物性評価を行った。つまり、トポロジー効果の制御を目指して、直鎖状と環状の可逆的高分子トポロジー変換の検討を行った。これまでに報告された直鎖状－環状の可逆的なトポロジー変換プロセスでは、有機溶媒中での酸化・還元試薬を用いるという欠点があったが、本研究は水中での光照射による低環境負荷のトポロジー変換を提案するものである。さらに、光開裂性環状ポリ乳酸ーポリエレンオキシドブロック共重合体を合成し、開裂によるゲル化を達成した。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2014年04月 -2017年03月 
    代表者 : 山本 拓矢, 手塚 育志, 井上 浄
     
    多環状高分子は、環内に複数の分岐点をもったfused型、環同士が1点で繋がったspiro型、環同士が直鎖で繋がったbridged型の3つの基本構造に分類できる。これらの異なる種類のトポロジーを複数合わせ持つ構造の合成はほとんど報告されていない。そこで、本研究ではDouble-Eightと呼ばれるspiro, bridgedの2つの基本構造を合わせ持つ新規多環状高分子トポロジー等の構築を行った。 また、新たな多環状高分子前駆体として等間隔の三箇所に官能基を持つ環状高分子の合成プロセスを検討した。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2011年04月 -2015年03月 
    代表者 : 山本 拓矢, 手塚 育志
     
    親水鎖にPEO、疎水鎖にPMAを有する直鎖状および環状ブロック共重合体を合成し、それぞれのミセルを作製した。これらのミセルの耐熱性・耐塩性を評価したところ、環状高分子から成るミセルが非常に高い安定性を示すことを見出した。 また、環状ホモポリ乳酸およびhead-to-head型、head-to-tail型の連結様式を持つ環状ステレオブロックポリ乳酸を合成し、DSCを用いた融点測定により、環と直鎖といった主鎖の「トポロジー」および「主鎖の方向」が熱的性質に与える影響を検討した。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2011年04月 -2014年03月 
    代表者 : 手塚 育志, 山本 拓矢
     
    新奇多環状高分子構造、特に３種の三環状２重縮合型(β、γおよびδグラフ図形)、さらに四環状３重縮合型（正四面体の展開図と同等図形）トポロジーの構築を達成した。また、環状・多環状高分子の「かたち」に基づくブレークスルー機能の創出を目的として、両親媒性環状・多環状ブロック共重合体によるミセル・ベシクル特性、および分子ねじれ単位を含む環状高分子によるメカノケミカル特性、についても検討した。これらを合わせて、高分子の「かたち」（トポロジー効果）に基づく新規な特性・機能を実現する「高分子トポロジー化学」の体系化を進めた。この成果は、ナノテクノロジーによる新材料創製を推進する基盤技術としても期待される。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2011年04月 -2013年03月 
    代表者 : 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：科学研究費助成事業
    研究期間 : 2009年 -2010年 
    代表者 : 山本 拓矢
     
    炭素数10および20の直鎖状ジチオールの片末端をワング樹脂に固定化した後、環化・脱離反応を行い、生成物のSEC測定を行ったところ、炭素数10および20の出発物質のいずれからも、環状ジスルフィドが生成することが認められた。さらに詳細な解析を行ったところ、炭素数20のジチオールからは、主に単量体、二量体、三量体が量体数に応じて収量が減少しながら生成したのに対し、炭素数10のものからは単量体を除く二量体以上の生成が確認された。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2005年 -2008年 
    代表者 : 手塚 育志, 足立 馨, 山本 拓矢, 足立 馨
     
    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.

教育活動情報

主要な担当授業

  • 応用生物化学Ａ（機能性高分子特論）
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 総合化学院
    キーワード : 高分子合成， 精密重合，リビング重合，ラジカル重合，カチオン重合，アニオン重合，配位重合、機能性高分子，高分子構造，高分子設計, 高分子溶液, 相分離挙動
  • 総合化学特論Ⅱ(Modern Trends in Organic Chemistry and Biological Chemistry)
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 総合化学院
    キーワード : コンピューター化学、有機化学、触媒、酵素、細胞分化、環状高分子化合物
  • 大学院共通授業科目（一般科目）：自然科学・応用科学
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 大学院共通科目
    キーワード : コンピューター化学、有機化学、触媒、酵素、細胞分化、環状高分子化合物
  • 大学院共通授業科目（一般科目）：自然科学・応用科学
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 大学院共通科目
    キーワード : Colloidal phenomena, Interfacial phenomena, Molecular Simulations
  • 応用化学特別講義
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 総合化学院
    キーワード : Colloidal phenomena, Interfacial phenomena, Molecular Simulations
  • 先端総合化学特論Ⅰ
    開講年度 : 2021年
    課程区分 : 博士後期課程
    開講学部 : 総合化学院
    キーワード : コンピューター化学、有機化学、触媒、酵素、細胞分化、環状高分子化合物
  • 先端総合化学特論Ⅱ
    開講年度 : 2021年
    課程区分 : 博士後期課程
    開講学部 : 総合化学院
    キーワード : Colloidal phenomena, Interfacial phenomena, Molecular Simulations
  • 応用化学学生実験Ⅴ
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 有機化学、高分子化学、安全教育、基礎実験、合成実験
  • 物質変換工学
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 有機合成，有機材料，化学プロセス，反応器設計，生体材料，高分子材料，分子機能，無機材料，複合材料，電子材料，光機能材料
  • 高分子化学Ⅱ
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 天然高分子、高分子の分子運動、高分子溶液、高分子固体・液晶、分子量測定法
  • 化学Ⅱ
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 全学教育
    キーワード : 有機化合物、官能基、分子構造、化学的性質、化学反応、機能性有機物、生体関連有機物質
  • 工学特別講義
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : Colloidal phenomena, Interfacial phenomena, Molecular Simulations
  • 高分子機能化学
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 高分子材料、導電性・イオン伝導性材料、光機能材料、分離・認識材料、メディカル機能材料、環境材料

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