研究者データベース

中島 祐(ナカジマ タスク)
先端生命科学研究院
准教授

基本情報

所属

  • 先端生命科学研究院

職名

  • 准教授

学位

  • 博士(理学)(北海道大学)

ホームページURL

科研費研究者番号

  • 80574350

ORCID ID

J-Global ID

研究キーワード

  • メカノケミストリー   液晶ゲル   犠牲結合   高分子科学   機能性高分子   高分子ゲル   

研究分野

  • ナノテク・材料 / 高分子材料 / 高分子ゲル

職歴

  • 2020年11月 - 現在 科学技術振興機構 さきがけ研究者
  • 2019年04月 - 現在 北海道大学大学院先端生命科学研究院 准教授
  • 2011年10月 - 2019年03月 北海道大学大学院先端生命科学研究院 助教
  • 2011年04月 - 2011年09月 東京大学大学院工学系研究科 博士研究員

学歴

  • 2006年04月 - 2011年03月   北海道大学大学院   理学院   生命理学専攻
  • 2002年04月 - 2006年03月   北海道大学   理学部

所属学協会

  • 日本化学会   高分子学会   

研究活動情報

論文

  • Tasuku Nakajima
    Proceedings of the National Academy of Sciences of the United States of America 2021年04月01日 [査読有り]
     
    Tough soft materials usually show strain softening and inelastic deformation. Here, we study the molecular mechanism of abnormally large nonsoftening, quasi-linear but inelastic deformation in tough hydrogels made of hyperconnective physical network and linear polymers as molecular glues to the network. The interplay of hyperconnectivity of network and effective load transfer by molecular glues prevents stress concentration, which is revealed by an affine deformation of the network to the bulk deformation up to sample failure. The suppression of local stress concentration and strain amplification plays a key role in avoiding necking or strain softening and endows the gels with a unique large nonsoftening, quasi-linear but inelastic deformation.
  • Tasuku Nakajima, Ken-ichi Hoshino, Honglei Guo, Takayuki Kurokawa, Jian Ping Gong
    Gels 2021年04月01日 [査読有り]
  • Haiyan Yin, Daniel R. King, Tao Lin Sun, Yoshiyuki Saruwatari, Tasuku Nakajima, Takayuki Kurokawa, Jian Ping Gong
    ACS Applied Materials & Interfaces 2020年11月04日 [査読有り]
  • Takahiro Matsuda, Runa Kawakami, Tasuku Nakajima, Jian Ping Gong
    Macromolecules 2020年10月27日 [査読有り]
  • Tomáš Sedlačík, Takayuki Nonoyama, Honglei Guo, Ryuji Kiyama, Tasuku Nakajima, Yoshihiro Takeda, Takayuki Kurokawa, Jian Ping Gong
    Chemistry of Materials 2020年10月13日 [査読有り]
  • Junchao Huang, Martin Frauenlob, Yuki Shibata, Lei Wang, Tasuku Nakajima, Takayuki Nonoyama, Masumi Tsuda, Shinya Tanaka, Takayuki Kurokawa, Jian Ping Gong
    Biomacromolecules 2020年10月12日 [査読有り]
  • M. Anamul Haque, Kunpeng Cui, Muhammad Ilyas, Takayuki Kurokawa, Alba Marcellan, Annie Brulet, Riku Takahashi, Tasuku Nakajima, J. Ping Gong
    Macromolecules 2020年06月12日 [査読有り][通常論文]
  • Kazuki Fukao, Tasuku Nakajima, Takayuki Nonoyama, Takayuki Kurokawa, Takahiko Kawai, Jian Ping Gong
    Macromolecules 2020年02月25日 [査読有り][通常論文]
  • Tasuku Nakajima, Takaharu Chida, Kei Mito, Takayuki Kurokawa, Jian Ping Gong
    Soft Matter 2020年 [査読有り][通常論文]
  • Ya Nan Ye, Kunpeng Cui, Tsutomu Indei, Tasuku Nakajima, Dominique Hourdet, Takayuki Kurokawa, Jian Ping Gong
    Macromolecules 2019年11月26日 [査読有り][通常論文]
  • Tasuku Nakajima, Yuhei Ozaki, Ryo Namba, Kumi Ota, Yuki Maida, Takahiro Matsuda, Takayuki Kurokawa, Jian Ping Gong
    ACS Macro Letters 8 11 1407 - 1412 2019年11月19日 [査読有り][通常論文]
  • Kunpeng Cui, Ya Nan Ye, Tao Lin Sun, Liang Chen, Xueyu Li, Takayuki Kurokawa, Tasuku Nakajima, Takayuki Nonoyama, Jian Ping Gong
    Macromolecules American Chemical Society ({ACS}) 2019年10月 [査読有り][通常論文]
  • Honglei Guo, Wei Hong, Takayuki Kurokawa, Takahiro Matsuda, Zi Liang Wu, Tasuku Nakajima, Masakazu Takahata, Taolin Sun, Ping Rao, Jian Ping Gong
    Macromoledules 52 18 7114 - 7122 2019年09月 [査読有り][通常論文]
  • Joji Murai, Tasuku Nakajima, Takahiro Matsuda, Katsuhiko Tsunoda, Takayuki Nonoyama, Takayuki Kurokawa, Jian Ping Gong
    Polymer 178 121686  Elsevier {BV} 2019年09月 [査読有り][通常論文]
  • 鍛えて成長するゲル―破壊による創造の材料科学―
    松田昂大, 中島 祐, 龔 剣萍
    現代化学 581 53 - 57 2019年08月 [査読無し][招待有り]
  • Hui Jie Zhang, Feng Luo, Yanan Ye, Tao Lin Sun, Takayuki Nonoyama, Takayuki Kurokawa, Tasuku Nakajima
    ACS Applied Polymer Materials American Chemical Society ({ACS}) 2019年08月 [査読有り][通常論文]
  • Guo Hui, Nakajima Tasuku, Hourdet Dominique, Marcellan Alba, Creton Costantino, Hong Wei, Kurokawa Takayuki, Gong Jian Ping
    Advanced Materials 31 25 2019年05月 [査読有り][通常論文]
  • Takahiro Matsuda, Tasuku Nakajima, Jian Ping Gong
    Chemistry of Materials American Chemical Society ({ACS}) 2019年05月 [査読有り][通常論文]
  • Takahiro Matsuda, Runa Kawakami, Ryo Namba, Tasuku Nakajima, Jian Ping Gong
    Science 363 6426 504  American Association for the Advancement of Science ({AAAS}) 2019年02月 [査読有り][通常論文]
  • Thanh-Tam Mai, Takahiro Matsuda, Tasuku Nakajima, Jian Ping Gong, Kenji Urayama
    Soft Matter Royal Society of Chemistry ({RSC}) 2019年 [査読有り][通常論文]
  • Ken-ichi Hoshino, Tasuku Nakajima, Takahiro Matsuda, Takamasa Sakai, Jian Ping Gong
    SOFT MATTER 14 47 9693 - 9701 2018年12月 [査読有り][通常論文]
     
    In this work, we intended to investigate the relationship between the swelling ratio Q and Young's modulus E of hydrogels from their contracted state to extreme swelling state and elucidate the underlining molecular mechanism. For this purpose, we used tetra-poly(ethylene glycol) (tetra-PEG) gel, whose network parameters are well known, as the polymer backbone, and we succeeded in tuning the swelling of the gel by a factor of 1500 times while maintaining the topological structure of the network unchanged, using an approach combining a molecular stent method and a PEG dehydration method. A master curve of Q-E, independent of the method of obtaining Q, was obtained. Using the worm-like chain model, the experimentally determined master curve can be well reproduced. We also observed that the uniaxial stress-strain curve of the hydrogel can be well predicted by the worm-like chain model using the structure parameters determined from the fitting of the Q-E experimental curve.
  • 刺激応答性発色ゲル
    堀端修人, 中島 祐, 龔 剣萍
    応用物理学会・有機分子・バイオエレクトロニクス分科会 会誌 29 4 232 - 235 2018年11月 [査読無し][招待有り]
  • Ran Shi, Tao Lin Sun, Feng Luo, Tasuku Nakajima, Takayuki Kurokawa, Yue Zhen Bin, Michael Rubinstein, Jian Ping Gong
    Macromolecules American Chemical Society ({ACS}) 2018年11月 [査読有り][通常論文]
  • Ryuji Kiyama, Takayuki Nonoyama, Susumu Wada, Shingo Semba, Nobuto Kitamura, Tasuku Nakajima, Takayuki Kurokawa, Kazunori Yasuda, Shinya Tanaka, Jian Ping Gong
    Acta Biomaterialia Elsevier {BV} 2018年10月 [査読有り][通常論文]
  • Riku Takahashi, Kouichi Shimano, Haruka Okazaki, Takayuki Kurokawa, Tasuku Nakajima, Takayuki Nonoyama, Daniel R. King, Jian Ping Gong
    Advanced Materials Interfaces 1801018  Wiley 2018年10月 [査読有り][通常論文]
  • Thanh-Tam Mai, Takahiro Matsuda, Tasuku Nakajima, Jian Ping Gong, Kenji Urayama
    Macromolecules American Chemical Society ({ACS}) 2018年07月 [査読有り][通常論文]
  • Ya Nan Ye, Martin Frauenlob, Lei Wang, Masumi Tsuda, Tao Lin Sun, Kunpeng Cui, Riku Takahashi, Hui Jie Zhang, Tasuku Nakajima, Takayuki Nonoyama, Takayuki Kurokawa, Shinya Tanaka, Jian Ping Gong
    Advanced Functional Materials 28 31 1801489  Wiley 2018年06月 [査読有り][通常論文]
  • Md. Tariful Islam Mredha, Yun Zhou Guo, Takayuki Nonoyama, Tasuku Nakajima, Takayuki Kurokawa, Jian Ping Gong
    Advanced Materials 30 9 1704937  2018年03月01日 [査読有り][通常論文]
     
    Natural structural materials (such as tendons and ligaments) are comprised of multiscale hierarchical architectures, with dimensions ranging from nano- to macroscale, which are difficult to mimic synthetically. Here a bioinspired, facile method to fabricate anisotropic hydrogels with perfectly aligned multiscale hierarchical fibrous structures similar to those of tendons and ligaments is reported. The method includes drying a diluted physical hydrogel in air by confining its length direction. During this process, sufficiently high tensile stress is built along the length direction to align the polymer chains and multiscale fibrous structures (from nano- to submicro- to microscale) are spontaneously formed in the bulk material, which are well-retained in the reswollen gel. The method is useful for relatively rigid polymers (such as alginate and cellulose), which are susceptible to mechanical signal. By controlling the drying with or without prestretching, the degree of alignment, size of superstructures, and the strength of supramolecular interactions can be tuned, which sensitively influence the strength and toughness of the hydrogels. The mechanical properties are comparable with those of natural ligaments. This study provides a general strategy for designing hydrogels with highly ordered hierarchical structures, which opens routes for the development of many functional biomimetic materials for biomedical applications.
  • Md. Anamul Haque, Kei Mito, Takayuki Kurokawa, Tasuku Nakajima, Takayuki Nonoyama, Muhammad Ilyas, Jian Ping Gong
    ACS Omega 3 1 55 - 62 2018年 [査読有り][通常論文]
     
    One-dimensional photonic crystals or multilayer films produce colors that change depending on viewing and light illumination angles because of the periodic refractive index variation in alternating layers that satisfy Bragg’s law. Recently, we have developed multilayered photonic hydrogels of two distinct bulk geometries that possess an alternating structure of a rigid polymeric lamellar bilayer and a ductile polyacrylamide (PAAm) matrix. In this paper, we focus on fabrication of composite gels with variable photonic band gaps by controlling the PAAm layer thickness. We report programmable angle-dependent and angle-independent structural colors produced by composite hydrogels, which is achieved by varying bulk and internal geometries. In the sheet geometry, where the lamellae are aligned parallel to the sheet surface, the photonic gel sheet exhibits strong angle-dependent colors. On the other hand, when lamellae are coaxially aligned in a cylindrical geometry, the gel rod exhibits an angle-independent color, in sharp contrast with the gel sheet. Rocking curves have been constructed to justify the diverse angle-dependent behavior of various geometries. Despite varying the bulk geometry, the tunable photonic gels exhibit strong mechanical performances and toughness. The distinct angle dependence of these tough photonic materials with variable band gaps could benefit light modulation in displays and sensor technologies.
  • Kazuki Fukao, Takayuki Nonoyama, Ryuji Kiyama, Kazuya Furusawa, Takayuki Kurokawa, Tasuku Nakajima, Jian Ping Gong
    ACS Nano 11 12 12103 - 12110 2017年12月26日 [査読有り][通常論文]
     
    Bone tissues possess excellent mechanical properties such as compatibility between strength and flexibility and load bearing owing to the hybridization of organic/inorganic matters with anisotropic structure. To synthetically mimic such an anisotropic structure of natural organic/inorganic hybrid materials, we carried out hydroxyapatite (HAp) mineralization in stretched tough double network (DN) hydrogels. Anisotropic mineralization of HAp took place in stretched hydrogels, as revealed by high brightness synchrotron X-ray scattering and transmission electron microscopic observation. The c-axis of mineralized HAp aligned along the stretching direction, and the orientation degree S calculated from scattering profiles increased with increasing in the elongation ratio λ of the DN gel, and S at λ = 4 became comparable to that of rabbit tibial bones. The morphology of HAp polycrystal gradually changed from spherical to unidirectional rod-like shape with increased elongation ratio. A possible mechanism for the anisotropic mineralization is proposed, which would be one of the keys to develop mechanically anisotropic organic/inorganic hybrid materials.
  • ダブルネットワークゲル( DN ゲル)の軟骨応用に向けた検討
    野々山貴行, 中島祐, 黒川孝幸, 北村信人, 安田和則, 龔剣萍
    FC Report 35 4 148 - 152 2017年10月 [査読無し][通常論文]
  • Muhammad Ilyas, Md. Anamul Haque, Youfeng Yue, Takayuki Kurokawa, Tasuku Nakajima, Takayuki Nonoyama, Jian Ping Gong
    MACROMOLECULES 50 20 8169 - 8177 2017年10月 [査読有り][通常論文]
     
    We study the effect of dehydration On the structure and mechanical properties of anisotropic lamellar hydrogels, consisting of alternative stacking of several thousands of nanoscale rigid bilayers from amphiphilic poly(dodecyl glyceryl itaconate) (PDGI) and submicroscale soft hydrogel layers from hydrophilic polyacrylamide (PAAm) networks. We found that the layered microstructure is well preserved with dehydration, and a ductile-brittle transition occurs at the critical water-content. This, transition is related to the rubbery-glassy transition of the PAAm layers, which occurs at 58 wt % water content and is much higher than 26 wt% of bulk PAAm hydrogels. Such specific behavior of the lamellar hydrogels indicates that the dynamics of the submicroscale PAAm hydrated layer intercalated between the rigid bilayers are very different from its bulk state.
  • Kei Mito, Md. Anamul Haque, Tasuku Nakajima, Maki Uchiumi, Takayuki Kurokawa, Takayuki Nonoyama, Jian Ping Gong
    POLYMER 128 373 - 378 2017年10月 [査読有り][通常論文]
     
    Novel, supramolecular, anisotropic hydrogels (called MC-PDGI gels) are presented in this study. These MC-PDGI gels consist of multi-cylindrical lipid bilayers aligned in a uniaxial manner and embedded in a soft hydrogel matrix. The bilayers and the hydrogel interact weakly due to hydrogen bonding. These MC-PDGI gels swell after exposure to water, which causes their volume and diameter to increase while simultaneously causing their length to decrease. This anisotropic swelling-induced contraction behavior is the result of competition between the isotropic elasticity of the hydrogel matrix and the interfacial tension of the lipid bilayers. Moreover, the MC-PDGI gels exhibit unique quasi one-dimensional diffusion behavior owing to the difficulty of molecular penetration through the multi-layered lipid bilayers. These materials would be useful for prolonged drug release or as an actuator. (C) 2017 Elsevier Ltd. All rights reserved.
  • Md. Tariful Islam Mredha, Nobuto Kitamura, Takayuki Nonoyama, Susumu Wada, Keiko Goto, Xi Zhang, Tasuku Nakajima, Takayuki Kurokawa, Yasuaki Takagi, Kazunori Yasuda, Jian Ping Gong
    BIOMATERIALS 132 85 - 95 2017年07月 [査読有り][通常論文]
     
    Soft supporting tissues in the human body, such as cartilages and ligaments, are tough materials and firmly fixed to bones. These soft tissues, once injured, cannot regenerate spontaneously in vivo. Developing tough and biocompatible hydrogels as artificial soft supporting tissues would substantially improve outcomes after soft tissue injury. Collagen is the main rigid component in soft connective tissues which is organized in various hierarchical arrays. We have successfully developed a novel class of collagen fibril-based tough hydrogels based on the double network (DN) concept using swim bladder collagen (SBC) extracted from Bester sturgeon fish. The DN hydrogels, SBC/PDMAAm, are composed of physically/chemically crosslinked anisotropic SBC fibril as the first network and neutral, biocompatible poly(N,N'-dimethylacrylamide) (PDMAAm) as the second network. The anisotropic structure of SBC fibril network, which is well retained in the DN hydrogels, is formed by free injection method, taking advantage of the excellent fibrillogenesis capacity of SBC. The denaturation temperature of collagen is improved in the DN hydrogels. These DN gels possess anisotropic swelling behavior, exhibit excellent mechanical properties comparable to natural cartilage. The 4 weeks implantation of the gels in the osteochondral defect of rabbit knee also shows excellent biomechanical performance in vivo. Furthermore, the hydroxyapatite (HAp) coated DN gels, HAp/SBC/PDMAAm gels, strongly bond to bone after 4 weeks. This new class of collagen-based hybrid DN gels, as soft and elastic ceramics, having good biomechanical performance and strong bonding ability with bone would expand the choice for designing next generation orthopedic implants such as artificial cartilage, bone defect repair material in the load bearing region of the body. (C) 2017 Elsevier Ltd. All rights reserved.
  • Feng Luo, Tao Lin Sun, Tasuku Nakajima, Takayuki Kurokawa, Xufeng Li, Honglei Guo, Yiwan Huang, Huijie Zhang, Jian Ping Gong
    POLYMER 116 487 - 497 2017年05月 [査読有り][通常論文]
     
    Tough hydrogels with adjustable stiffness are expected for adapting application as various biomaterials. Oppositely charged polyelectrolytes form tough and self-healing physical polyion-complex (PIC) hydrogels via formation of inter-chain ionic bonds with a wide distribution in bond strength. The strong bonds serve as permanent crosslinking to impart elasticity and the weak bonds as reversible sacrificial bonds to dissipate energy and to self-heal. In this work, we fabricate four PIC hydrogels using four positively charged trimethyl-ammonium monomers with slightly different chemical moieties and a same negatively charged polymer. The obtained PIC hydrogels all show high toughness but large difference in stiffness, extensibility, and self-recovery kinetics. With slight difference in the monomer structure of the polycations, the modulus of the hydrogels varies over two orders in magnitude, from 0.36 to 56 MPa, and the difference in elongation at break is up to five times. The presence of acryloyl moiety and methyl moiety increase the stiffness of the hydrogels. In the temperature range studied, all the four PIC hydrogels exhibit the rheological simple behaviours, following the time-temperature superposition principle. The four samples show quite different dynamic relaxation spectra over wide frequency range, revealing large difference in the strength distribution of dynamic ionic bonds. SEM observation reveals quite different phase separation structure for the four samples, in which the polymer chain stiffness should play an important role. This understanding of structure-properties of the PIC hydrogels will merit the designing of various supramolecular tough hydrogels and therefore broaden the scope of hydrogels for the applications as biomaterials. (C) 2017 Elsevier Ltd. All rights reserved.
  • Tao Lin Sun, Feng Luo, Wei Hong, Kunpeng Cui, Yiwan Huang, Hui Jie Zhang, Daniel R. King, Takayuki Kurokawa, Tasuku Nakajima, Jian Ping Gong
    MACROMOLECULES 50 7 2923 - 2931 2017年04月 [査読有り][通常論文]
     
    Recently, many tough and self-healing hydro gels have been developed based on physical bonds as reversible sacrificial bonds. As breaking and re-forming of physical bonds are time-dependent, these hydrogels are viscoelastic and the deformation rate and temperature pronouncedly influence their fracture behavior. Using a polyampholyte hydrogel as a model system, we observed that the time temperature superposition principle is obeyed not only for the small strain rheology but also for the large strain hysteresis energy dissipation and the fracture energy below a certain temperature. The three processes possess the same shift factors that obey the equation of Williams, Landel, and Ferry (WLF) time temperature equivalence. The fracture energy F scales with the crack velocity V-c over a wide velocity range as Gamma similar to V-c(alpha) (alpha = 0.21). The exponent alpha of the power law is well-related to the exponent kappa of the relaxation modulus G(t) similar to t(-kappa) (kappa = 0.26), obeying the prediction alpha = kappa/(1 + kappa) from classic viscoelasticity theory. These results show that the fracture energy of the polyampholyte gel is dominated by the bulk viscoelastic energy dissipated around the crack tip. This investigation gives an insight into designing tough and self-healing hydrogels and predicting their fracture behaviors from their dynamic mechanical spectrum.
  • Yiwan Huang, Daniel R. King, Tao Lin Sun, Takayuki Nonoyama, Takayuki Kurokawa, Tasuku Nakajima, Jian Ping Gong
    ADVANCED FUNCTIONAL MATERIALS 27 9 2017年03月 [査読有り][通常論文]
     
    Tough hydrogels have shown strong potential as structural biomaterials. These hydrogels alone, however, possess limited mechanical properties (such as low modulus) when compared to some load-bearing tissues, e.g., ligaments and tendons. Developing both strong and tough soft materials is still a challenge. To overcome this obstacle, a new material design strategy has been recently introduced by combining tough hydrogels with woven fiber fabric to create fiber reinforced soft composites (FRSCs). The new FRSCs exhibit extremely high toughness and tensile properties, far superior to those of the neat components, indicating a synergistic effect. Here, focus is on understanding the role of energy dissipation of the soft matrix in the synergistic toughening of FRSCs. By selecting a range of soft matrix materials, from tough hydrogels to weak hydrogels and even a commercially available elastomer, the toughness of the matrix is determined to play a critical role in achieving extremely tough FRSCs. This work provides a good guide toward the universal design of soft composites with extraordinary fracture resistance capacity.
  • Tasuku Nakajima, Kenta Hiwatashi, Jian Hu, Takayuki Kurokawa, Jian Ping Gong
    KOBUNSHI RONBUNSHU 74 4 311 - 318 2017年 [査読有り][通常論文]
     
    A gradient particle double network gel (P-DN gel) which exhibits unique conformation changes has been fabricated. A gradient P-DN gel consists of polyanion microgel particles with a concentration gradient and a poly(acrylamide) (PAAm) network as a matrix. In order to make the gradient structure, the gel precursor solution containing acrylamide, the microgel particles and some other additives was electrophoresed before its polymerization. When the gradient P-DN gel was soaked in pure water, it macroscopically formed a helical conformation due to a swelling mismatch induced by the gradient structure of the microgels. Moreover, when the gradient P-DN gel was immersed in an ethanol/water mixed solution and in a NaCl aqueous solution, the conformation of the gel dynamically changed to flat- and cylinder-shapes, respectively. These unique conformation changes can be qualitatively explained by considering not only the swelling mismatch but also an edge effect.
  • 刺激応答性構造色と異方的物性を示すリオトロピック液晶ゲル
    中島祐, 龔剣萍
    液晶 20 4 212 - 217 2016年10月 [査読有り][招待有り]
  • Takayuki Nonoyama, Susumu Wada, Ryuji Kiyama, Nobuto Kitamura, Md. Tariful Islam Mredha, Xi Zhang, Takayuki Kurokawa, Tasuku Nakajima, Yasuaki Takagi, Kazunori Yasuda, Jian Ping Gong
    ADVANCED MATERIALS 28 31 6740 - + 2016年08月 [査読有り][通常論文]
     
    On implanting hydroxyapatite-mineralized tough hydrogel into osteochondral defects of rabbits, osteogenesis spontaneously penetrates into the gel matrix owing to the semi-permeablility of the hydrogel. The gradient layer (around 40 mu m thick) contributes quite strong bonding of the gel to bone. This is the first success in realizing the robust osteointegration of tough hydrogels, and the method is simple and feasible for practical use.
  • Sadia Nazneen Karobi, Tao Lin Sun, Takayuki Kurokawa, Feng Luo, Tasuku Nakajima, Takayuki Nonoyama, Jian Ping Gong
    MACROMOLECULES 49 15 5630 - 5636 2016年08月 [査読有り][通常論文]
     
    Polyampholyte (PA) hydrogels are a new class of tough and selfhealing supramolecular hydrogels that have a potential as load-bearing soft materials. Studying on the creep behavior of these hydrogels and understanding the molecular mechanism are important for prediction of lifetime of the materials. In the present work, we study the creep rupture dynamics of the PA hydrogels with and without chemical cross-linking, in a certain observation time window. We have found that above some critical loading stress both physical and lightly chemically cross-linked hydrogels undergo creep rupture while moderately chemically cross-linked hydrogel resists creep flow. To elucidate the molecular mechanism, we have further compared the creep behaviors of the physical and lightly chemically cross-linked samples. The creep rate of the samples decreases with the creep time, following a power law relation, regardless of the loading stress variation. The fracture time of both of these hydrogels exponentially decreases with the increase of the loading stress, following the same master curve at high loading stress region, while the behavior of the two samples becomes different in the low loading stress region. We have explained the delayed fracture dynamics at high loading stress region in terms of a relatively weak strong bond rupture mechanism.
  • Ao-kai Zhang, Jun Ling, Kewen Li, Guo-dong Fu, Tasuku Nakajima, Takayuki Nonoyama, Takayuki Kurokawa, Jian Ping Gong
    JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS 54 13 1227 - 1236 2016年07月 [査読有り][通常論文]
     
    In this study, controlled amount of dangling ends is introduced to the two series of poly(ethylene glycol)-based hydrogel networks with three and four crosslinking functionality by using click chemistry. The structure of the gels with regulated defect percentage is confirmed by comparing the results of low-field NMR characterization and Monte Carlo simulation. The mechanical properties of these gels were characterized by tensile stress-strain behaviors of the gels, and the results are analyzed by Gent model and Mooney-Rivlin model. The shear modulus of the swollen gels is found to be dependent on the functionality of the network, and decreases with the defect percentage. Furthermore, the value of shear modulus well obeys the Phantom model for all the gels with varied percentage of the defects. The maximum extension ratio, obtained from the fitting of Gent model, is also found to be dependent on the functionality of the network, and does not change with the defect percentage, except at very high defect percentage. The value of the maximum extension ratio is between that predicted from Phantom model and the Affine model. This indicates that at the large deformation, the fluctuation of the crosslinking points is suppressed for some extend but still exists. Polymer volume fractions at various defect percentages obtained from prediction of Flory-Rehner model are found to be in well agreement with the swelling experiment. All these results indicate that click chemistry is a powerful method to regulate the network structure and mechanical properties of the gels. (C) 2016 Wiley Periodicals, Inc.
  • Hui Jie Zhang, Tao Lin Sun, Ao Kai Zhang, Yumihiko Ikura, Tasuku Nakajima, Takayuki Nonoyama, Takayuki Kurokawa, Osamu Ito, Hiroyuki Ishitobi, Jian Ping Gong
    ADVANCED MATERIALS 28 24 4884 - 4890 2016年06月 [査読有り][通常論文]
     
    A series of physical double-network hydrogels is synthesized based on an amphiphilic triblock copolymer. The gel, which contains strong hydrophobic domains and sacrificial dynamic bonds of hydrogen bonds, is stiff and tough, and even stiffens in concentrated saline solution. Furthermore, due to its supramolecular structure, the gel features improved self-healing and self-recovery abilities.
  • Abu Bin Ihsan, Tao Lin Sun, Takayuki Kurokawa, Sadia Nazneen Karobi, Tasuku Nakajima, Takayuki Nonoyama, Chanchal Kumar Roy, Feng Luo, Jian Ping Gong
    MACROMOLECULES 49 11 4245 - 4252 2016年06月 [査読有り][通常論文]
     
    Recently, polyampolytes have been discovered to form hydrogels that possess high toughness, full resilience, and self-healing between two cut surfaces. The self-healing of this class of hydrogels is based on the re-forming of the multiple Tonic bonds at the fractured surfaces, in which the mobility of the polymer segments and strength of the ionic bonds play an important role. In this work, we study the effects of healing temperature and chemistry of the polyampholyte hydrogels (chemical cross -linker density and chemical structure of the monomers) on the healing kinetics and healing efficiency. The high healing temperature substantially accelerates the self-healing kinetics. Chemical cross-linking reduces the self-healing efficiency. Monomers with more hydrophobic feature give a low self-healing efficiency. For polyampholyte physical hydrogels with a softening temperature below the room temperature, excellent-healing efficiency (similar to 84% on average and maximum 99%) was observed without any external stimuli.- We found a correlation between the self-healing efficiency and the fraction of dynamic bonds in the total bonds for relatively soft samples, which is an evidence that the self healing is due to the re-forming of dynamic bonds.
  • Feng Luo, Tao Lin Sun, Tasuku Nakajima, Daniel R. King, Takayuki Kurokawa, Yu Zhao, Abu Bin Ihsan, Xufeng Li, Honglei Guo, Jian Ping Gong
    MACROMOLECULES 49 7 2750 - 2760 2016年04月 [査読有り][通常論文]
     
    Oppositely charged homopolyelectrolytes were found to form strong, tough, and self-healing polyion-complex (PIC) hydrogels, similar to polyampholytes (PA) which have opposite charges randomly distributed on the same polymer chains. The excellent mechanical performances of these two novel hydrogels are the results of dynamic ionic bonds formation between entangled polymer chains. For the PIC system, only interchain bonding occurs, while for the PA system both inter- and intrachain bonding exist. In addition, the ion pairs are expected to form stronger bonding in the PIC system than those in the PA system. In this work, we performed a comparative study of PIC hydrogels with the PA hydrogels. The PIC hydrogels are synthesized by sequential homopolymerization of cationic and anionic monomers at varied formulation, and their swelling and mechanical properties are systematically studied in comparison to the PA hydrogels that were synthesized from random copolymerization of anionic monomers and cationic monomers of the similar formulation. Different from the PA system which only forms tough hydrogels around zero net charge composition without chemical cross-linking, the PIC system forms tough physical hydrogels even at weakly off balanced charge composition. At the charge-balanced composition, the low entanglement concentration of homocharged polyelectrolyte chains leads to tough PIC hydrogels formation at much lower concentrations than that of PA hydrogels. As a result, the PIC hydrogels are much tougher than the PA hydrogels prepared at the same monomer composition. In similar to PA hydrogels, the PIC hydrogels also exhibit broad dynamic mechanical spectra, indicating the formation of ion complexes with widely ranged bond strength. The PIC hydrogels have strong viscoelasticity in comparison with PA hydrogels. However, the two systems show the similar activation energies of the dynamic mechanical spectra. The SEM microstructural observation shows that the PIC hydrogels have segregated structure while PA hydrogels are more homogeneous.
  • Honglei Guo, Takayuki Kurokawa, Masakazu Takahata, Wei Hong, Yoshinori Katsuyama, Feng Luo, Jamil Ahmed, Tasuku Nakajima, Takayuki Nonoyama, Jian Ping Gong
    MACROMOLECULES 49 8 3100 - 3108 2016年04月 [査読有り][通常論文]
     
    We report, for the first time, the quantitative measurement of the local electric potential of brittle polyelectrolyte hydrogels using the microelectrode technique (MET). Given the solid-like nature of the hydrogels, the difficulty of applying MET is how to make a good contact of the microelectrode to the hydrogel. Poor local contact substantial underestimates the potential. We observed that, the potential measured decays exponentially with the increase of capillary diameter of the microelectrode. This behavior is related to the capillary wall thickness that determines the contact distance of the electrode probe to the hydrogel. The characteristic decay length in respective to the wall thickness is very close to the local Debye length around the capillary. The latter is much larger than that of the bath solution due to the reverse osmosis effect. By using microelectrodes with a tip wall thickness less than the local Debye length, the Donnan potential of polyelectrolyte gel could be accurately measured. Using a micromanipulator, the inserting process of the microelectrode is precisely controlled, and the depth profile of electric potential in the hydrogels can be measured with a spatial resolution down to similar to 5 nm. From the spatial distribution of potential, the microstructure of hydrogels both in bulk and near the surface, the thickness of ultrathin hydrogels, and the heterogeneous layered structure of composite gels, can be determined accurately. The MET established in this work provides a powerful tool for direct characterization of the spatial distribution of electric potential of hydrogels.
  • Takahiro Matsuda, Tasuku Nakajima, Yuki Fukuda, Wei Hong, Takamasa Sakai, Takayuki Kurokawa, Ung-il Chung, Jian Ping Gong
    MACROMOLECULES 49 5 1865 - 1872 2016年03月 [査読有り][通常論文]
     
    Double network (DN) gels, consisting of a brittle first and flexible second network, have been known to be extremely tough and functional hydrogels. In a DN gel subjected to force, the brittle first network breaks prior to the fracture of the flexible network. This process, referred to as internal fracture, dissipates energy and increases the energy required to completely fracture DN gels. Such internal fracture macroscopically appears as a yielding-like phenomenon. The aim of this paper is to investigate the relationship between the yield point and the first network molecular structure of DN gels to more deeply understand the internal fracture mechanism of DN gels. To achieve this goal, we synthesized DN gels having a tetra-PEG first network, which is known to be a nearly ideal and well-controlled network gel. We have found that yielding of the DN gels occurs when the first network strands reach their extension limit (finite extensibility), regardless of their deformation mode. This conclusion not only helps by further understanding the toughening mechanism of DN gels but also allows for the design of DN gels with precisely controlled mechanical properties.
  • 水戸京, 中島祐, 野々山貴行, 龔剣萍
    高分子論文集 73 2 157 - 165 2016年 [査読有り][招待有り]
     
    Lipid molecules form anisotropic self-assembled structures such as worm-like micelles or lipid bilayers. Recently the authors have successfully introduced and immobilized uniaxially-oriented lipid bilayers of poly(dodecyl glyceryl itaconate) (PDGI) into the polyacrylamide (PAAm) gel matrix to obtain stable gel-bilayer composites (called PDGI/PAAm gels) with anisotropic structure and functions, such as unidirectional swelling or anisotropic diffusion. One question about this complek is why such a dynamic lipid bilayer structure can be well-stabilized in PAAm gels. In this paper, we focus on the bilayer structure of the PDGI/PAAm gels. In the fast part, the stabilization mechanism of lipid bilayers in the gels, due to hydrogen bonding between PDGI and PAAm, is discussed. In the second part, structure transition and function modification of the PDGI/PAAm gels by insertion of more lipid molecules into bilayers is investigated.
  • Kunpeng Cui, Tao Lin Sun, Takayuki Kurokawa, Tasuku Nakajima, Takayuki Nonoyama, Liang Chen, Jian Ping Gong
    SOFT MATTER 12 43 8833 - 8840 2016年 [査読有り][通常論文]
     
    Recently, we have developed a series of charge balanced polyampholyte (PA) physical hydrogels by random copolymerization in water, which show extraordinarily high toughness, self-healing ability and viscoelasticity. The excellent performance of PA hydrogels is ascribed to dynamic ionic bond formation through inter-and intra-chain interactions. The randomness results in ionic bonds of wide strength distribution, the strong bonds, which serve as permanent crosslinking, imparting the elasticity, while the weak bonds reversibly break and re-form, dissipating energy. In this work, we developed a simple physical method, called a pre-stretching method, to promote the performance of PA hydrogels. By imposing a pre-stretching on the sample in the as-prepared state, ion complexation during dialysis is prominently accelerated and the final performance is largely promoted. Further analysis suggests that the strong bond formation induced by pre-stretching is responsible for the change in final performance. Pre-stretching decreases the entropy of the system and increases the chain alignment, resulting in an increased possibility for strong bond formation.
  • Riku Takahashi, Yumihiko Ikura, Daniel R. King, Takayuki Nonoyama, Tasuku Nakajima, Takayuki Kurokawa, Hirotoshi Kuroda, Yoshihiro Tonegawa, Jian Ping Gong
    SOFT MATTER 12 23 5081 - 5088 2016年 [査読有り][通常論文]
     
    Most studies on hydrogel swelling instability have been focused on a constrained boundary condition. In this paper, we studied the mechanical instability of a piece of disc-shaped hydrogel during free swelling. The fast swelling of the gel induces two swelling mismatches; a surface-inner layer mismatch and an annulus-disc mismatch, which lead to the formation of a surface crease pattern and a saddle-like bulk bending, respectively. For the first time, a stripe-like surface crease that is at a right angle on the two surfaces of the gel was observed. This stripe pattern is related to the mechanical coupling of surface instability and bulk bending, which is justified by investigating the swelling-induced surface pattern on thin hydrogel sheets fixed onto a saddle-shaped substrate prior to swelling. A theoretical mechanism based on an energy model was developed to show an anisotropic stripe-like surface crease pattern on a saddle-shaped surface. These results might be helpful to develop novel strategies for controlling crease patterns on soft and wet materials by changing their three-dimensional shape.
  • Chanchal Kumar Roy, Hong Lei Guo, Tao Lin Sun, Abu Bin Ihsan, Takayuki Kurokawa, Masakazu Takahata, Takayuki Nonoyama, Tasuku Nakajima, Jian Ping Gong
    ADVANCED MATERIALS 27 45 7344 - + 2015年12月 [査読有り][通常論文]
     
    Developing nonspecific, fast, and strong adhesives that can glue hydrogels and biotissues substantially promotes the application of hydrogels as biomaterials. Inspired by the ubiquitous adhesiveness of bacteria, it is reported that neutral polyampholyte hydrogels, through their self-adjustable surface, can show rapid, strong, and reversible adhesion to charged hydrogels and biological tissues through the Coulombic interaction.
  • Koshiro Sato, Tasuku Nakajima, Toshiyuki Hisamatsu, Takayuki Nonoyama, Takayuki Kurokawa, Jian Ping Gong
    ADVANCED MATERIALS 27 43 6990 - + 2015年11月 [査読有り][通常論文]
     
    Novel, tough, strong, and self-healable polyacrylamide (PAAm) gels are fabricated by inducing an appropriate phase-separation structure using a poor solvent. The phase separation induces a gel-glass-like transition of the PAAm gels, providing the gels an anomalously high modulus (211 MPa), fracture stress (7.13 MPa), and fracture energy (4.16 x 10(4) J m(-2)), while keeping a high solvent content (approximate to 60 vol%).
  • Feng Luo, Tao Lin Sun, Tasuku Nakajima, Takayuki Kurokawa, Abu Bin Ihsan, Xufeng Li, Honglei Guo, Jian Ping Gong
    ACS MACRO LETTERS 4 9 961 - 964 2015年09月 [査読有り][通常論文]
     
    Tough hydrogels with facile processability to reform into various shapes are required in many practical applications. In this work, we reported that a novel, tough, and self-healing physical hydrogel based on polyion complex (PIC) can be dissolved in 4 M NaCl solution to form a PIC solution. The PIC solution can be easily reprocessed into various shapes, such as thin films, sheets, fibers, and capsules, by using simple methods, such as casting and injection, while maintaining excellent mechanical properties comparable to, or even better than, the original hydrogel. The reprocessability and robust mechanical properties of PIC hydrogels are promising for practical applications in soft materials, especially in 3D/4D printing technology.
  • Jamil Ahmed, Tetsurou Yamamoto, Honglei Guo, Takayuki Kurokawa, Takayuki Nonoyama, Tasuku Nakajima, Jian Ping Gong
    MACROMOLECULES 48 15 5394 - 5401 2015年08月 [査読有り][通常論文]
     
    A simplified model describing the sliding friction of hydrogel on solid surface by dynamic adsorption of the polymer chains is proposed on the basis of polymer adsorption-repulsion theory. This dynamic adsorption model is used to analyze the friction results of zwitterionic hydrogels sliding over glass substrates with different substrate wettability, hydrogel swelling degree, ionic strength, and pH of bath solution. The adsorption time tau(b) of polymer strands is found to decrease with the increase in sliding velocity or the Weissenberg number as a result of stretching. The adsorption time tau(0)(b), and the adsorption energy U-ads at stress-free condition, which are characteristic for each friction system, are also estimated. Roughly, a master curve is observed for the normalized adsorption lifetime tau(b)/tau(0)(b) and the Weissenberg number, with less dependence on the adsorption energy and the bulk properties of the gels in the observed experimental conditions. Thus, the dynamic adsorption model successfully correlates the frictional behavior of hydrogels with the adsorption dynamics of polymer strands, which gives insight into the molecular design of hydrogels with predefined frictional properties for biomedical applications.
  • 高強度ゲルをつくる
    中島祐, 龔剣萍
    高分子 64 6 367 - 369 2015年05月 [査読無し][招待有り]
  • Feng Luo, Tao Lin Sun, Tasuku Nakajima, Takayuki Kurokawa, Yu Zhao, Koshiro Sato, Abu Bin Ihsan, Xufeng Li, Honglei Guo, Jian Ping Gong
    ADVANCED MATERIALS 27 17 2722 - + 2015年05月 [査読有り][通常論文]
     
    A series of tough polyion complex hydrogels is synthesized by sequential homopolymerization of cationic and anionic monomers. Owing to the reversible interpolymer ionic bonding, the materials are self-healable under ambient conditions with the aid of saline solution. Furthermore, self-glued bulk hydrogels can be built from their microgels, which is promising for 3D/4D printing and the additive manufacturing of hydrogels.
  • Xufeng Li, Takayuki Kurokawa, Riku Takahashi, Md. Anamul Haque, Youfeng Yue, Tasuku Nakajima, Jan Ping Gong
    MACROMOLECULES 48 7 2277 - 2282 2015年04月 [査読有り][通常論文]
     
    We report that polymers can support bilayer membranes to form physical hydrogels of self-healing and tunable isotropic/anisotropic structure. The system consists of poly(dodecyl glyceryl itaconate) (PDGI) which forms lamellar bilayers and polyacrylamide (PAAm) which adsorbs on the bilayer surfaces via hydrogen bond formation. Adsorption of PAAm brings two effects: disturbs the bilayer packing and causes bending of the bilayers; increases the effective thickness of the bilayers and enhances the repulsion between the bilayers due to excluded volume effect. Competition of these two effects brings about sharp superstructure transition from isotropic multilayer foam phase to unidirectionally aligned lamellar phase. Accompanied by this structure transition, the bulk hydrogel exhibits isotropic/anisotropic swelling. The physical gels exhibit high tensile strength and self-healing properties that can be understood by the sacrificial bonds mechanism.
  • Xufeng Li, Takayuki Kurokawa, Riku Takahashi, Md. Anamul Haque, Youfeng Yue, Tasuku Nakajima, Jan Ping Gong
    MACROMOLECULES 48 7 2277 - 2282 2015年04月 [査読有り][通常論文]
     
    We report that polymers can support bilayer membranes to form physical hydrogels of self-healing and tunable isotropic/anisotropic structure. The system consists of poly(dodecyl glyceryl itaconate) (PDGI) which forms lamellar bilayers and polyacrylamide (PAAm) which adsorbs on the bilayer surfaces via hydrogen bond formation. Adsorption of PAAm brings two effects: disturbs the bilayer packing and causes bending of the bilayers; increases the effective thickness of the bilayers and enhances the repulsion between the bilayers due to excluded volume effect. Competition of these two effects brings about sharp superstructure transition from isotropic multilayer foam phase to unidirectionally aligned lamellar phase. Accompanied by this structure transition, the bulk hydrogel exhibits isotropic/anisotropic swelling. The physical gels exhibit high tensile strength and self-healing properties that can be understood by the sacrificial bonds mechanism.
  • 小さな力で多彩な色をだす構造色ゲル―新しいメカノクロミック材料の合成法とその応用
    中島祐, グン 剣萍
    化学 70 4 32 - 36 2015年03月 [査読無し][招待有り]
  • Md. Tariful Islam Mredha, Xi Zhang, Takayuki Nonoyama, Tasuku Nakajima, Takayuki Kurokawa, Yasuaki Takagid, Jian Ping Gong
    JOURNAL OF MATERIALS CHEMISTRY B 3 39 7658 - 7666 2015年 [査読有り][通常論文]
     
    Marine collagen has been attracting attention as a medical material in recent times due to the low risk of pathogen infection compared to animal collagen. Type I collagen extracted from the swim bladder of Bester sturgeon fish has excellent characteristics such as high denaturation temperature, high solubility, low viscosity and an extremely fast rate to form large bundle of fibers under certain conditions. These specific characteristics of swim bladder collagen (SBC) permit us to create stable, disk shaped hydrogels with concentric orientation of collagen fibers by the controlled diffusion of neutral buffer through collagen solution at room temperature. However, traditionally used animal collagens, e.g. calf skin collagen (CSC) and porcine skin collagen (PSC), could not form any stable and oriented structure by this method. The mechanism of the superstructure formation of SBC by a diffusion induced gelation process has been explored. The fast fibrillogenesis rate of SBC causes a quick squeezing out of the solvent from the gel phase to the sol phase during gelation, which builds an internal stress at the gel-sol interface. The tensile stress induces the collagen molecules of the gel phase to align along the gel-sol interface direction to give this concentric ring-shaped orientation pattern. On the other hand, the slow fibrillogenesis rate of animal collagens due to the high viscosity of the solution does not favor the ordered structure formation. The denaturation temperature of SBC increases significantly from 31 degrees C to 43 degrees C after gelation, whereas that of CSC and PSC were found to increase a little. Rheology experiment shows that the SBC gel has storage modulus larger than 15 kPa. The SBC hydrogels with thermal and mechanical stability have potential as bio-materials for tissue engineering applications.
  • Tasuku Nakajima, Corentin Durand, Xu Feng Li, Md. Anamul Haque, Takayuki Kurokawa, Jian Ping Gong
    SOFT MATTER 11 2 237 - 240 2015年 [査読有り][通常論文]
     
    PDGI-PAAm gels with well oriented lipid bilayers show a quasi-unidirectional shrinkage upon uniaxial stretching along the bilayers. They shrink largely parallel to the bilayer but slightly perpendicular to it in order not to increase the bilayer area and its interfacial energy. Such an anisotropic deformation can be well-modelled based on classical theories for gel networks and lipid layers.
  • Tao Lin Sun, Feng Luo, Takayuki Kurokawa, Sadia Nazneen Karobi, Tasuku Nakajima, Jian Ping Gong
    SOFT MATTER 11 48 9355 - 9366 2015年 [査読有り][通常論文]
     
    Recently, charge balanced polyampholytes (PA) have been found to form tough and self-healing hydrogels. This class of physical hydrogels have a very high equilibrated polymer concentration in water (ca. 40-50 wt%), and are strongly viscoelastic. They are synthesized by random copolymerization of equal amounts of oppositely charged monomers at a high concentration, followed by a dialysis process of the small counter-ions and co-ions in water. The randomly distributed, opposite charges of the polymer form multiple ionic bonds of intra-and inter-chains with strength distribution. The strong interchain bonds, stabilized by topological entanglement, serve as quasi-permanent crosslinks, imparting the elasticity, while the weak bonds, both inter-and intra-chains, reversibly break and re-form to dissipate energy to toughen the materials. In this work, we intend to clarify the structure of the physical PA hydrogels from the tensile behaviors of the PA hydrogels. To clarify the structure and its formation mechanism, we analysed the tensile behaviors of the samples before and after the dialysis. We separated the quasi-permanent crosslinking of strong inter-chain bonds and the dynamic crosslinking of weak inter-chain bonds by using a combined model that consists of the Upper Convected Maxwell model and the Gent strain hardening model. The model fitting of the tensile behaviors extracts quantitative structural parameters, including the densities of weak and strong inter-chain bonds and the theoretical finite extensibility of polymer chains. Based on the fitting results of the combined model, the structural parameters of partial chains at a fixed observation time, including the Kuhn number, Kuhn length, and chain conformation, are determined using the scaling theory. The effects of monomer concentration at preparation, the effect of dialysis and the initial strain rate on the dynamic structure of PA gels, are discussed based on these analyses.
  • Zi Liang Wu, Riku Takahashi, Daisuke Sawada, Md. Arifuzzaman, Tasuku Nakajima, Takayuki Kurokawa, Jian Hu, Jian Ping Gong
    MACROMOLECULES 47 20 7208 - 7214 2014年10月 [査読有り][通常論文]
     
    Diffusion of multivalent metallic ions into aqueous solution of rigid, negatively charged macromolecules of high concentration is an effective approach to prepare macroscopically anisotropic hydrogels. However, the mechanism for superstructure formation is still not clear. By observing the mixing process of a small drop of CaCl2 solution with solution of a rigid polyanion, poly(2,2'-disulfonyl-4,4'-benzidine terephthalamide) (PBDT), under the polarizing optical microscope, the diffusion profile of Ca2+ and detailed anisotropic gelation process of PBDT are revealed. Diffusion of Ca2+ into the surrounding PBDT solution immediately induces the formation of physical liquid crystalline (LC) gel with concentric alignment of PBDT. The thickness d of this region increases with diffusion time t, obeying the diffusion law d similar to t1/2. A thin ring of constant width (similar to 100 mu m) with radial alignment of PBDT appears at the diffusion/reaction front, ahead of the concentric alignment region. When two drops of CaCl2 fluxes meet, their outside thin rings interact with each other and the PBDT in this contacting region orients +/- 45 degrees to the midline of the two drops. From these observations, we rationally contend that the internal stress induced by the contraction of gel phase is responsible for the ion diffusion-induced PBDT orientations. This structure formation mechanism gives insight into other diffusion-directed anisotropic gelation systems.
  • Feng Luo, Tao Lin Sun, Tasuku Nakajima, Takayuki Kurokawa, Yu Zhao, Abu Bin Ihsan, Hong Lei Guo, Xu Feng Li, Jian Ping Gong
    MACROMOLECULES 47 17 6037 - 6046 2014年09月 [査読有り][通常論文]
     
    Recently, we have reported that polyampholytes, synthesized from free radical copolymerization of anionic monomer and cationic monomer, form physical hydrogels of high toughness and self-healing. The random distribution of the opposite charges forms ionic bonds of a wide distribution of strength. The strong bonds serve as permanent cross-links, imparting elasticity, whereas the weak bonds serves as reversible sacrificial bonds by breaking and reforming to dissipate energy. In this work, we focus on the rupture behaviors of the polyampholyte physical hydrogel, P(NaSS-co-MPTC), copolymerized from sodium p-styrenesulfonate (NaSS) and 3-(methacryloylamino)propyltrimethylammonium chloride (MPTC). Tensile test and pure shear test were performed at various stretch rates in the viscoelastic responses region of the material. Tensile test showed yielding, strain softening, and strain hardening, revealing the dually cross-linked feature of the gel. Pure shear test showed crack blunting at the notched tip and a large yielding zone with butterfly shaped birefringence pattern ahead of the crack tip. After blunting, crack advanced at steady-state velocity with a constant angle. The conditions for the occurrence of crack blunting and variables governing the crack advancing angle are discussed. We found that even for these highly stretchable samples, significant blunting only occurs when the tensile fracture stress sigma(f) is larger than modulus E by a factor of about 2, in consistent with Huis theoretical prediction for elastic materials. The crack advancing angle theta was found to be proportional to sigma(y)/E over a wide stretch rate range, where sigma(y) is the yielding stress. In addition, the fracture energy was correlated to small strain modulus by a power law in the viscoelastic response region. This systematic study will merit revealing the fracture mechanism of tough viscoelastic materials including biological tissues and recently developed tough and highly stretchable hydrogels.
  • Youfeng Yue, Takayuki Kurokawa, Md Anamul Haque, Tasuku Nakajima, Takayuki Nonoyama, Xufeng Li, Itsuro Kajiwara, Jian Ping Gong
    NATURE COMMUNICATIONS 5 2014年08月 [査読有り][通常論文]
     
    Photonic crystals with tunability in the visible region are of great interest for controlling light diffraction. Mechanochromic photonic materials are periodically structured soft materials designed with a photonic stop-band that can be tuned by mechanical forces to reflect specific colours. Soft photonic materials with broad colour tunability and fast colour switching are invaluable for application. Here we report a novel mechano-actuated, soft photonic hydrogel that has an ultrafast-response time, full-colour tunable range, high spatial resolution and can be actuated by a very small compressive stress. In addition, the material has excellent mechanical stability and the colour can be reversibly switched at high frequency more than 10,000 times without degradation. This material can be used in optical devices, such as full-colour display and sensors to visualize the time evolution of complicated stress/strain fields, for example, generated during the motion of biological cells.
  • Riku Takahashi, Zi Liang Wu, Md Arifuzzaman, Takayuki Nonoyama, Tasuku Nakajima, Takayuki Kurokawa, Jian Ping Gong
    NATURE COMMUNICATIONS 5 2014年08月 [査読有り][通常論文]
     
    Biomacromolecules usually form complex superstructures in natural biotissues, such as different alignments of collagen fibres in articular cartilages, for multifunctionalities. Inspired by nature, there are efforts towards developing multiscale ordered structures in hydrogels (recognized as one of the best candidates of soft biotissues). However, creating complex superstructures in gels are hardly realized because of the absence of effective approaches to control the localized molecular orientation. Here we introduce a method to create various superstructures of rigid polyanions in polycationic hydrogels. The control of localized orientation of rigid molecules, which are sensitive to the internal stress field of the gel, is achieved by tuning the swelling mismatch between masked and unmasked regions of the photolithographic patterned gel. Furthermore, we develop a double network structure to toughen the hydrogels with programmed superstructures, which deform reversibly under large strain. This work presents a promising pathway to develop superstructures in hydrogels and should shed light on designing biomimetic materials with intricate molecular alignments.
  • Jian Hu, Takayuki Kurokawa, Tasuku Nakajima, Zi Liang Wu, Song Miao Liang, Jian Ping Gong
    MACROMOLECULES 47 11 3587 - 3594 2014年06月 [査読有り][通常論文]
     
    We have found that lightly cross-linked neutral hydrogels containing microgels of densely cross-linked polyelectrolyte show high strength and toughness. These kinds of hydrogels, named as microgel-reinforced (MR) hydrogels, are a two-phase composite, where the disperse phase is the microgel with the double network (DN) structure and the continuous phase is the soft neutral gel matrix. The brittle polyelectrolyte network of the DN microgels, though in disperse phase, also serves as sacrificial bonds to toughen the material, similar to conventional DN gels. In this paper, we study the internal fracture process of the MR gel under uniaxial tension. The tensile stress-strain curve of the MR gel is charaterized by four regions according to its differential curve: elastic region (0 < epsilon < 1), preyielding region (1 < epsilon < 3), yielding region (3 < epsilon < 7), and strain hardening region (epsilon > 7). The morphology change of microgels in the reswollen MR gels after prestretching tells that the internal fracture of microgels, which occurs beyond the elastic region (epsilon > 1), is anisotropic. That is, the short chains in the tensile direction fracture first (1 < epsilon < 3); at large stretching, both the long chains in the tensile direction and the short chains in the transverse direction fracture (3 < epsilon < 7), followed by the fracture of the long chains in the transverse direction (epsilon > 7). These anisotropic fracture behaviors are in similar to bulk DN gels. Moreover, at each stage of the tensile process, large microgels always fracture prior to small ones and own higher fracture efficiency in the chain rupture than the smaller ones. This size effect is attributed to the stress concentration effect around the two poles of large microgels induced by the close distance from their neighboring microgels.
  • Jamil Ahmed, Honglei Guo, Tetsurou Yamamoto, Takayuki Kurokawa, Masakazu Takahata, Tasuku Nakajima, Jian Ping Gong
    MACROMOLECULES 47 9 3101 - 3107 2014年05月 [査読有り][通常論文]
     
    Polyzwitterionic materials, which have both cationic and anionic groups in each repeating unit of polymer, show excellent antibiofouling properties. In this study, the surface friction of carboxybetaine type zwitterionic hydrogels, poly(N-(carboxymethyl)-N,N-dimethy1-2-(methacryloyloxy)-ethanaminium, inner salt) (PCDME), against glass substrates were investigated in aqueous solutions. The friction measurement was performed using a rheometer with parallel plate geometry and the sliding interface was monitored during the measurement. The frictional stress on glass was high in water and it showed weak dependence on pressure as long as the two sliding surfaces were in complete contact. The results performed in solutions with varied ionic strength revealed that the high friction on glass substrates has an electrostatic origin. The electrostatic potential measurement revealed that the PCDME gels have an isoelectric point at pH 8.5. Since the glass substrates carrying negative charges in pure water, the gel and the glass have electrostatic attraction in water. Study on the effect of pH has shown that below pH 8.5, attraction between the positively charged gels and negatively charged glass gives high friction, while above pH 8.5, the electrical double layer repulsion between two negatively charged surfaces gives low friction. From these results, it is concluded that although the PCDME gels behave like neutral gels in the bulk properties, their surface properties sensitively change with pH and ionic strength of the medium.
  • 一軸配向二分子膜によるハイドロゲルの高靱性化
    中島 祐, グン剣萍
    超分子研究会アニュアルレビュー 34 14 - 15 2014年03月 [査読無し][招待有り]
  • Saika Ahmed, Tasuku Nakajima, Takayuki Kurokawa, Md Anamul Haque, Jian Ping Gong
    POLYMER 55 3 914 - 923 2014年02月 [査読有り][通常論文]
     
    Tough double network (DN) hydrogels are a kind of interpenetrating network (IPN) gels with a contrasting structure; they consist of a rigid and brittle 1st network with dilute, densely cross-linked short chains and a soft and ductile 2nd network with concentrated, loosely cross-linked long chains. In this work, we focus on how the brittle gel changes into a tough one by increasing the amount of ductile component. By comparing the molecular structures of the individual first network and second network gels, we found that the true key mechanical factor that governs the brittle ductile transition is the fracture stress ratio of the two networks, sigma(f,2)/sigma(f,1). This ratio is related to the density ratio of elastically effective polymer strands of the two networks, nu(e,2)/nu(e,1), where the inter-network topological entanglement makes dominant contribution to nu(e,2). When nu(e,2)/nu(e,1) < k = 3.8-9.5, the second network fractures right after the fracture of the first network, and the gels are brittle. When nu(e,2)/nu(e,1) > k, only the first network fractures. As a result, the brittle first network serves as sacrificial bonds, imparting toughness of DN gels. The study also confirms that the load transfer between the two networks is via inter-network topological entanglement. This result provides essential information to design tough materials based on the double network concept. (C) 2014 Elsevier Ltd. All rights reserved.
  • Yu Zhao, Tasuku Nakajima, Jing Jing Yang, Takayuki Kurokawa, Jian Liu, Jishun Lu, Shuji Mizumoto, Kazuyuki Sugahara, Nobuto Kitamura, Kazunori Yasuda, A. U. D. Daniels, Jian Ping Gong
    ADVANCED MATERIALS 26 3 436 - 442 2014年01月 [査読有り][通常論文]
  • Md. Arifuzzaman, Zi Liang Wu, Riku Takahashi, Takayuki Kurokawa, Tasuku Nakajima, Jian Ping Gong
    Macromolecules 46 22 9083 - 9090 2013年11月26日 [査読有り][通常論文]
     
    In this paper, we developed several kinds of ordered structures in hydrogels with different geometries and sizes by harnessing heterogeneous swelling induced mechanical instability, i.e., surface creasing, which leads to molecular orientations along the tensile direction. These hydrogels were synthesized by polymerization of a cationic monomer, N-[3-(N,N-dimethylamino) propyl] acrylamide methyl chloride quaternary (DMAPAA-Q) and a chemical cross-linker, in the presence of a small amount of the semirigid polyanion, poly(2,2′-disulfonyl-4,4′-benzidine terephthalamide) (PBDT), as dopant. During the swelling process of as-prepared gels, surface creasing occurs and induces formation of a lattice-like periodic ordered structure, which is maintained in the swollen gels due to the formation of strong polyion complex. Besides this structure formed at the central part of gel sheets, PBDTs align parallel to the gel boundary at the edge of gels with a cuboid, disk, or ring shape. The size of the two regions with different structures and the size of each unit of lattice-like pattern are related to the geometry and size of the gels. The formation of different ordered structures was found due to the different mechanical instabilities at different parts of the gel during the heterogeneous swelling. This work presenting the creation of ordered structures in hydrogels by tuning the mechanical instability will pave the way to develop other functional structured materials and merit revealing the formation mechanism of ordered structures in soft biotissues during the nonequilibrium growth. © 2013 American Chemical Society.
  • Tao Lin Sun, Takayuki Kurokawa, Shinya Kuroda, Abu Bin Ihsan, Taigo Akasaki, Koshiro Sato, Md Anamul Haque, Tasuku Nakajima, Jian Ping Gong
    NATURE MATERIALS 12 10 932 - 937 2013年10月 [査読有り][通常論文]
     
    Hydrogels attract great attention as biomaterials as a result of their soft and wet nature, similar to that of biological tissues. Recent inventions of several tough hydrogels show their potential as structural biomaterials, such as cartilage. Any given application, however, requires a combination of mechanical properties including stiffness, strength, toughness, damping, fatigue resistance and self-healing, along with biocompatibility. This combination is rarely realized. Here, we report that polyampholytes, polymers bearing randomly dispersed cationic and anionic repeat groups, form tough and viscoelastic hydrogels with multiple mechanical properties. The randomness makes ionic bonds of a wide distribution of strength. The strong bonds serve as permanent crosslinks, imparting elasticity, whereas the weak bonds reversibly break and re-form, dissipating energy. These physical hydrogels of supramolecular structure can be tuned to change multiple mechanical properties over wide ranges by using diverse ionic combinations. This polyampholyte approach is synthetically simple and dramatically increases the choice of tough hydrogels for applications.
  • Tao Lin Sun, Takayuki Kurokawa, Shinya Kuroda, Abu Bin Ihsan, Taigo Akasaki, Koshiro Sato, Md Anamul Haque, Tasuku Nakajima, Jian Ping Gong
    NATURE MATERIALS 12 10 932 - 937 2013年10月 [査読有り][通常論文]
     
    Hydrogels attract great attention as biomaterials as a result of their soft and wet nature, similar to that of biological tissues. Recent inventions of several tough hydrogels show their potential as structural biomaterials, such as cartilage. Any given application, however, requires a combination of mechanical properties including stiffness, strength, toughness, damping, fatigue resistance and self-healing, along with biocompatibility. This combination is rarely realized. Here, we report that polyampholytes, polymers bearing randomly dispersed cationic and anionic repeat groups, form tough and viscoelastic hydrogels with multiple mechanical properties. The randomness makes ionic bonds of a wide distribution of strength. The strong bonds serve as permanent crosslinks, imparting elasticity, whereas the weak bonds reversibly break and re-form, dissipating energy. These physical hydrogels of supramolecular structure can be tuned to change multiple mechanical properties over wide ranges by using diverse ionic combinations. This polyampholyte approach is synthetically simple and dramatically increases the choice of tough hydrogels for applications.
  • You Feng Yue, M. Anamul Haque, Takayuki Kurokawa, Tasuku Nakajima, Jian Ping Gong
    Advanced Materials 25 22 3106 - 3110 2013年06月11日 [査読有り][通常論文]
     
    A lamellar hydrogel with high toughness, exhibiting ternary stimuli-responsive structural color changes has been synthesized. The gel consists of alternating hard layers of a polymeric surfactant (PDGI) and soft layers of interpenetrating networks of poly(acrylamide)-poly(acrylic acid). Reversible, wide range switching of the stop-band position was achieved using different external stimuli of temperature, pH, and stress/strain. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  • Tasuku Nakajima, Yuki Fukuda, Takayuld Kurokawa, Takamasa Sakai, Ung-il Chung, Jian Ping Gong
    ACS MACRO LETTERS 2 6 518 - 521 2013年06月 [査読有り][通常論文]
     
    To investigate the effect of inhomogeneity in the first network on the enormously high toughness of double network (DN) gels, we fabricated DN gels with a nearly homogeneous first network structure (named St-TPEG/PAAm DN gels) based on tetra-PEG (TPEG) gels via a molecular stent method. The St-TPEG/PAAm DN gels also show excellent mechanical properties and yielding-like phenomena comparable to conventional DN gels. This result demonstrates that the inhomogeneity within the first network is not essential for the specific toughening mechanism of DN gels. On the other hand, the St-TPEG/PAAm DN gels and conventional DN gels undergo substantially different fracture processes before the yielding point. This suggests the importance of a "homogenization process" for the yielding of DN gels. Since the St-TPEG/PAAm DN gels consist of a well-defined first network, they may serve as model DN gels in the future for further studies on fracture processes of DN gels.
  • Tasuku Nakajima, Yuki Fukuda, Takayuld Kurokawa, Takamasa Sakai, Ung-il Chung, Jian Ping Gong
    ACS MACRO LETTERS 2 6 518 - 521 2013年06月 [査読有り][通常論文]
     
    To investigate the effect of inhomogeneity in the first network on the enormously high toughness of double network (DN) gels, we fabricated DN gels with a nearly homogeneous first network structure (named St-TPEG/PAAm DN gels) based on tetra-PEG (TPEG) gels via a molecular stent method. The St-TPEG/PAAm DN gels also show excellent mechanical properties and yielding-like phenomena comparable to conventional DN gels. This result demonstrates that the inhomogeneity within the first network is not essential for the specific toughening mechanism of DN gels. On the other hand, the St-TPEG/PAAm DN gels and conventional DN gels undergo substantially different fracture processes before the yielding point. This suggests the importance of a "homogenization process" for the yielding of DN gels. Since the St-TPEG/PAAm DN gels consist of a well-defined first network, they may serve as model DN gels in the future for further studies on fracture processes of DN gels.
  • Haiyan Yin, Taigo Akasaki, Tao Lin Sun, Tasuku Nakajima, Takayuki Kurokawa, Takayuki Nonoyama, Toshio Taira, Yoshiyuki Saruwatari, Jian Ping Gong
    JOURNAL OF MATERIALS CHEMISTRY B 1 30 3685 - 3693 2013年 [査読有り][通常論文]
     
    Polyzwitterionic materials, which have both cationic and anionic groups in the polymeric repeat unit, show excellent anti-biofouling properties and are drawing more attention in the biomedical field. In this study, we have successfully synthesized novel single network hydrogels and double network (DN) hydrogels from the zwitterionic monomer, N-(carboxymethyl)-N,N-dimethyl-2-(methacryloyloxy) ethanaminium, inner salt (CDME). The polyCDME (PCDME) single network hydrogel behaves like a hydrophilic neutral hydrogel and its properties are not sensitive to temperature, pH, or ionic strength over a wide range. DN hydrogels using the poly(2-acrylamido-2-methylpropanesulfonic) (PAMPS) as the first network and PCDME as the second network, having a Young's modulus of 0.2-0.9 MPa, possess excellent mechanical strength (fracture stress: 1.2-1.4 MPa, fracture strain: 2.2-6.0 mm/mm) and toughness (work of extension at fracture: 0.9-2.4 MJ m(-3)) depending on the composition ratio of PCDME to PAMPS. The strength and toughness of the optimized PAMPS/PCDME DN is comparable to the normal PAMPS/PAAm DN hydrogels that use poly(acrylamide) (PAAm) as the second network. By macrophage adhesion test, both the PCDME hydrogels and the PAMPS/PCDME DN hydrogels have shown excellent anti-biofouling properties. These results demonstrate that the PCDME-based DN hydrogels have high potential as a novel soft and wet biomaterial.
  • Tasuku Nakajima, Takayuki Kurokawa, Saika Ahmed, Wen-li Wu, Jian Ping Gong
    SOFT MATTER 9 6 1955 - 1966 2013年 [査読有り][通常論文]
     
    Previously we revealed that the high toughness of double network hydrogels (DN gels) derives from the internal fracture of the brittle network during deformation, which dissipates energy as sacrificial bonds. In this study, we intend to elucidate the detailed internal fracture process of DN gels. We quantitatively analysed the tensile hysteresis and re-swelling behaviour of a DN gel that shows a well-defined necking and strain hardening, and obtained the following new findings: (1) fracture of the 1st network PAMPS starts far below the yielding strain, and 90% of the initially load-bearing PAMPS chains already break at the necking point. (2) The dominant internal fracture process occurs in the necking and hardening region, although the softening mainly occurs before necking. (3) The internal fracture efficiency is very high, 85% of the work is used for the internal fracture and 9% of all PAMPS chains break at sample failure. (4) The internal fracture is anisotropic, fracture occurs perpendicular to the tensile direction, in preference to the other two directions, but the fracture anisotropy decreases in the hardening region. Results (1) and (2) are in agreement with a hierarchical structural model of the PAMPS network. Based on these findings, we present a revised description of the fracture process of DN gels.
  • Abu Bin Ihsan, Tao Lin Sun, Shinya Kuroda, Md. Anamul Haque, Takayuki Kurokawa, Tasuku Nakajima, Jian Ping Gong
    Journal of Materials Chemistry B 1 36 4555 - 4562 Royal Society of Chemistry ({RSC}) 2013年 [査読有り][通常論文]
     
    Our recent study has revealed that neutral polyampholytes form tough physical hydrogels above a critical concentration C-m,C-c by forming ionic bonds of wide strength distribution. In this work, we systematically investigate the behavior of a polyampholyte system, poly(NaSS-co-DMAEA-Q), randomly copolymerized from oppositely charged monomers, sodium p-styrenesulfonate (NaSS) and acryloyloxethyltrimethylammonium chloride (DMAEA-Q) without and with a slight chemical cross-linking. A phase diagram of formulation has been constructed in the space of monomer concentration C-m and cross-linker density C-MBAA. Three phases are observed for the as-synthesized samples: homogeneous solution at dilute C-m, phase separation at semi-dilute C-m, and homogenous gel at concentrated C-m. Above a critical C-m,C-c, the polyampholyte forms a supramolecular hydrogel with high toughness by dialysis of the mobile counter-ions, which substantially stabilizes both the intra-and inter chain ionic bonds. The presence of the chemical cross-linker (C-MBAA > 0) brings about a shift of the tough gel phase to lower C-m,C-c. The tough polyampholyte gel, containing similar to 50 wt % water, is highly stretchable and tough, exhibits fracture stress of sigma(b) similar to 0.4 MPa, fracture strain of epsilon(b) similar to 30, and the work of extension at fracture W-ext similar to 4 MJ m(-3). These values are at the level of most tough soft materials. Owing to the reversible ion bonds, the poly(NaSS-co-DMAEA-Q) gels also exhibit complete self-recovery (100%) and high fatigue resistance upon repeated large deformation.
  • Jian Hu, Takayuki Kurokawa, Tasuku Nakajima, Tao Lin Sun, Tiffany Suekama, Zi Liang Wu, Song Miao Liang, Jian Ping Gong
    MACROMOLECULES 45 23 9445 - 9451 2012年12月 [査読有り][通常論文]
     
    Double-network hydrogels (DN gels) have aroused considerable interest because of their excellent mechanical strength and toughness, low sliding friction, good biocompatibility, as well as wide tunability in components. By revisiting DN gels, we provide an ingenious way to fabricate a kind of strong and tough microgel-reinforced hydrogels (MR gels), that densely cross-linked polyelectrolyte microgels of poly(2-acrylamido-2-methylpropanesulfonic sodium) (PNaAMPS) (replacing the densely crosslinked PNaAMPS macro-network for conventional DN gels) are incorporated into sparsely cross-linked neutral polyacrylamide (PAAm) matrix. The structure of MR gels can be considered as a two-phase composite, where the disperse phase is the rigid DN microgels, and the continuous phase is the soft PAAm matrix. Similar to DN gels, MR gels show the irreversible energy dissipation in the hysteresis measurement, demonstrating the permanent fracture of the brittle PNaAMPS phase. Thus, the discontinuous brittle phase also serves as sacrificial bonds. Through quantitative comparison of the hysteresis curves with DN gels and monitoring the morphology change of the embedded microgels in MR gels during the real-time stretching process, we conclude that the DN microgels in MR gels show four times higher in fracture efficiency of the sacrificial bonds than bulk DN gels at the same strain, as a result of the stress concentration around the microgels.
  • Tasuku Nakajima, Hitomi Sato, Yu Zhao, Shinya Kawahara, Takayuki Kurokawa, Kazuyuki Sugahara, Jian Ping Gong
    ADVANCED FUNCTIONAL MATERIALS 22 21 4426 - 4432 2012年11月 [査読有り][通常論文]
     
    Double-network hydrogels (DN gels), despite their high water content, are the strongest and toughest soft and wet materials available. However, in conventional DN gels, which show extraordinarily high mechanical performance comparable to that of industrial rubbers, the first network must be a strong polyelectrolyte and this requirement greatly hinders the widespread application of these gels. A general method involving the use of a molecular stent for the synthesis of tough DN gels using any hydrophilic polymer as the first network is reported. This is the first reported method for the synthesis of tough DN gels using various neutral or weak polyelectrolyte hydrogels as the first network. This method helps extend the DN gel concept to various functional polymers and may increase the number of applications of hydrogels in various fields.
  • Jian Hu, Takayuki Kurokawa, Kenta Hiwatashi, Tasuku Nakajima, Zi Liang Wu, Song Miao Liang, Jian Ping Gong
    MACROMOLECULES 45 12 5218 - 5228 2012年06月 [査読有り][通常論文]
     
    In this work, the mechanical behavior of sparsely cross-linked, neutral polyacrylamide (PAAm) hydrogels containing densely cross-linked polyelectrolyte microgels of poly(2-acrylamido-2-methylpropanesulfonic sodium) (PNaAMPS) were studied systematically by varying the formulations. The microgel-reinforced (MR) hydrogels have a two-phase composite structure, where the disperse phase is the rigid double-network (DN) microgels, and the continuous phase is the soft PAAm matrix. At the optimal formulation, the MR gels showed high mechanical strength and toughness, comparable to conventional DN hydrogels. The two critical parameters for the substantial enhancement of mechanical strength and toughness of MR gels are the concentration of PNaAMPS microgel and the molar ratio of the PAAm to the PNaAMPS in the microgel phase. Selective dyeing of the embedded microgels in MR gels allowed for visualization of the deformation of microgels, and we found that the local strain of microgels was much smaller than the global strain applied on MR gels; this indicates that isostress model (Reuss's model) is more suitable than isostrain model (Voigt's model) for this composite system.
  • Tasuku Nakajima, Hidemitsu Furukawa, Yoshimi Tanaka, Takayuki Kurokawa, Jian Ping Gong
    JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS 49 17 1246 - 1254 2011年09月 [査読有り][通常論文]
     
    Introduction of soft filler in a hard body, which is one of the common toughening methods of hard polymeric materials, was applied for further toughening of robust double network (DN) hydrogels composed of poly(2-acrylamido-2-methylpropanesulfonic acid) gels (PAMPS gels) as the first component and polyacrylamide (PAAm) as the second component. The fracture energy of the DN gels with the void structure (called void-DN gels) became twice when the volume fraction of void was 1-3 vol % and the void diameter was much larger than the Flory radius of the PAAm chains. Such toughening was induced by wider range of internal fracture of the PAMPS network derived from partial stress concentration near void structure. Considering the mechanical tests and the dynamic light scattering results, it is implied that the absence of the load-bearing PAAm structure inside the void is important for the toughening. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1246-1254, 2011
  • Hiroko Itagaki, Takayuki Kurokawa, Hidemitsu Furukawa, Tasuku Nakajima, Yukiteru Katsumoto, Jian Ping Gong
    MACROMOLECULES 43 22 9495 - 9500 2010年11月 [査読有り][通常論文]
     
    In the previous studies, we have developed double network hydrogels (DN gels) with extra ordinarily high mechanical strength and toughness although the gels contain 90 wt % of water In this study we investigated the effect of water content on the mechanical behavior of the DN gel consists of poly(2 acrylamido 2 methylpropanesulfonic acid) gels (PAMPS gels) as the first network and polyacrylamide gels (PAAm gels) as the second network When the DN gel was dried gradually from its equilibrium swelling state (90 wt % water content) it exhibited a ductile behavior with a very high fracture stress and strain at an intermediate water content c (65 wt % < c < 75%) and then became brittle upon further decreasing in water content (c < 60 wt %) The behavior of the DN gel was compared with the corresponding single network gels, PAMPS and PAAm It is found that at the intermediate water content the fracture stress and strain of PAAm gel reached maximum, and the brittle ductile change of DN gel upon with the change in water content was the results of the change in the mechanical properties of PAAm network
  • Tasuku Nakajima, Naoyuki Takedomi, Takayuki Kurokawa, Hidemitsu Furukawa, Jian Ping Gong
    POLYMER CHEMISTRY 1 5 693 - 697 2010年07月 [査読有り][通常論文]
     
    The creation of double network hydrogels (DN gels), which show extremely high mechanical strength, enable hydrogels to be applied both in medical and industrial fields. However, one obstacle for various applications is the lack of formability of DN gels, owing to the brittleness of the first network PAMPS gels. In order to overcome this problem, we synthesized free-shaped DN gels (called PVA-DN gels) by using a physically cross-linked PVA gel as an "internal mold". PVA-DN gels can form any complex shapes and their mechanical properties were comparable to those of conventional DN gels. This study may expand the application of tough hydrogels.
  • Tasuku Nakajima, Hidemitsu Furukawa, Jian Ping Gong, Eric K. Lin, Wen-li Wu
    POLYMER NETWORKS: SYNTHESIS, PROPERTIES, THEORY AND APPLICATIONS 291-292 1 122 - + 2010年 [査読有り][通常論文]
     
    The long-standing pursuit of a synthetic equivalent to tissue cartilage has sprouted significant new activities in strategies for new material synthesis, among them a noticeable one being the double-network hydrogels (DN-gels) scheme. DN-gels were prepared from the combination of an anionic polyelectrolyte network and a lightly crosslinked neutral polymer. These hydrogels exhibit an intriguing combination of properties intrinsic to natural cartilage: a low surface friction coefficient and a fracture toughness much higher than either of the constituent materials. The reinforcement of a hard, brittle polymer gel with a soft, viscoelastic neutral polymer is counter-intuitive. Based on our recent results from neutron scattering measurements, we proposed a deformation mechanism where the molecular association between these two polymers plays a pivotal role. In this work, we further evaluate the proposed mechanism by performing mechanical measurements on DN-gel samples with different polyelectrolyte network structure. The experimental results provide qualitative support for the proposed deformation mechanism.
  • Tasuku Nakajima, Hidemitsu Furukawa, Yoshimi Tanaka, Takayuki Kurokawa, Yoshihito Osada, Jian Ping Gong
    MACROMOLECULES 42 6 2184 - 2189 2009年03月 [査読有り][通常論文]
     
    We elucidate why the anomalous high strength of double network gels is obtained when the second network is polymerized without any cross-linkers. We have synthesized truly independent-DN gels (named "t-DN" gels), which do not have any covalent bonds between the first and the second networks, and showed that the t-DN gels cannot be toughened by the un-cross-linked second network. It means that the high strength of Usual DIN gels without the cross-linker of the second network is actually achieved by the interconnection between the two networks through covalent bonds (so usual DN gels were named "c-DN" gels). Further, we found that the t-DN gels become stronger than the c-DN gels when the second network is loosely cross-linked. As the t-DN gels have a more simple structure than the c-DN gels, we expect that the toughening mechanism of DN gels will be clarified by studying the t-DN gels in the future.
  • Yasunori Kawauchi, Yoshimi Tanaka, Hidemitsu Furukawa, Takayuki Kurokawa, Tasuku Nakajima, Yoshihito Osada, Jian Ping Gong
    Journal of Physics: Conference Series 184 012016  2009年 [査読有り][通常論文]
     
    We propose a simple method to obtain double network (DN) hydrogels containing 85-90wt% water with various kinds of mechanical performance by taking advantage of the heterogeneity of the first network: By synthesizing the first network in a poor solvent that enhancing the heterogeneity of the network, the DN gel exhibits rich mechanical behavior: from brittle, ductile (necking), to paste-like. For a proper heterogeneity, a distinct necking deformation with extensibility of about 20 times is observed for post-necking gels. The necking gels have a high initial modulus (0.1-0.5 MPa) and high mechanical toughness (nominal fracture stress: 1 MPa), both values are similar to that of living tissues. © 2009 IOP Publishing Ltd.
  • Tasuku Nakajima, Takayuki Kurokawa, Hidemitsu Furukawa, Qiu Ming Yu, Yoshimi Tanaka, Yoshihito Osada, Jian Ping Gong
    CHINESE JOURNAL OF POLYMER SCIENCE 27 1 1 - 9 2009年01月 [査読有り][招待有り]
     
    Living tissues work with fantastic functions in soft and wet gel-like state. Thus, hydrogels have attracted much attention as excellent soft and wet materials, suitable for making artificial organs for medical treatments. However, conventional hydrogels are mechanically too weak for practical uses. We have created double network (DN) hydrogels with extremely high mechanical strength in order to overcome this problem. DN gels are interpenetrating network (IPN) hydrogels consisting of rigid polyelectrolyte and soft neutral polymer. Their excellent mechanical properties cannot be explained by the standard fracture theories. In this paper, we discuss about the toughening mechanism of DN gels in accordance with their characteristic behavior, such as large hysteresis and necking phenomenon. We also describe the results on tissue engineering application of DN gels.
  • Mei Huang, Hidemitsu Furukawa, Yoshimi Tanaka, Tasuku Nakajima, Yoshihito Osada, Jian Ping Gong
    MACROMOLECULES 40 18 6658 - 6664 2007年09月 [査読有り][通常論文]
     
    The double network (DN) gels, composed of a minor component, chemically cross-linked polyelectrolyte (first network), and the major one, linear neutral polymer (second network), exhibit anomalously high mechanical strengths. In this study, adopting the concentration of the second polymer as the experimental parameter, we investigate the relation between the mechanical strength and the dynamics of polymer concentration fluctuation. The former is measured by compression and tearing tests; the latter is measured by a special dynamic light scattering technique (called SMILS) suitable for polymer gels. The mechanical strength is enhanced when the concentration is so high that the second polymer chains strongly entangle each other. The main finding of SMILS is that the diffusion constant of the concentration fluctuation of the second polymer is increased by the existence of the first network despite the minority of the first component (<(1)/(10) in monomer ratio to the second component). This indicates that there is entanglement also between the first and the second polymers. The inter-species entanglement and inhomogeneities of the first network suggested in our previous study [Macromolecules 2004, 37, 5370] give support to the crack model concerned with yielding around the crack tip, which explains the high mechanical strength.

その他活動・業績

特許

受賞

  • 2020年09月 北海道大学 全学教育科目に係る授業アンケートにおけるエクセレント・ティーチャーズ
     
    受賞者: 中島祐
  • 2019年05月 高分子学会 広報委員会パブリシティ賞
     
    受賞者: 中島 祐
  • 2019年01月 RSC Soft Matter Presentation Award
     
    受賞者: 中島 祐
  • 2017年01月 北海道大学 平成28年度北海道大学研究総長賞・奨励賞
     
    受賞者: 中島 祐
  • 2016年05月 公益社団法人高分子学会 平成27年度高分子研究奨励賞
     
    受賞者: 中島 祐
  • 2015年03月 北海道大学 平成26年度北海道大学研究総長賞・奨励賞
     
    受賞者: 中島 祐
  • 2015年03月 北海道大学 平成26年度北海道大学教育総長賞・奨励賞
     
    受賞者: 中島 祐
  • 2014年08月 北海道大学 全学教育科目に係る授業アンケートにおけるエクセレント・ティーチャーズ
     
    受賞者: 中島 祐
  • 2013年10月 日本ゴム協会 第25回エラストマー討論会 優秀発表賞
     
    受賞者: 中島 祐
  • 2012年10月 Soft Matter Poster Prize at the 9th International Gel Symposium
     
    受賞者: 中島 祐
  • 2012年05月 日本化学会 優秀講演賞(産業)
     
    受賞者: 中島 祐

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 基盤研究(S)
    研究期間 : 2017年05月 -2022年03月 
    代表者 : グン 剣萍, 黒川 孝幸, 野々山 貴行, キング ダニエル, 中島 祐
     
    本年度は主に、ハードマター相の犠牲結合が複合材料の強靭化に及ぼす効果を解明した。最初に、mmスケールの多様な二次元長方格子(犠牲結合)を設計し、高性能3Dプリンターによって作製した。次いで、高靱性の柔らかい材料をマトリックス相として格子と複合させ、巨視的なスケールでのダブルネットワーク複合体を創製した。二次元格子の骨格の太さを制御した実験より、引張試験における多段階の格子の破断(すなわち犠牲結合原理の発現)は、二次元格子の強度がマトリックスの強度を上回った場合に生じることが分かった。また格子の節の数を制御した実験より、節の数を増やすほど引張試験時における格子の破断イベント数が増えるために材料が強靭となるが、強靭性はある一定の値で頭打ちになることが分かった。さらに多様な材質による二次元格子を検討した結果、どのような材質を用いても複合材料は強靭になったことから、格子の化学的性質(例えば表面の接着性)は強靭化に大きな影響を及ぼさず、格子とマトリックスの力学物性の関係性が強靭化度合の決定の主要因であることが明らかとなった。 次いで、多様な二次元・三次元格子を設計し、格子のポアソン比を変化させた複合材料を創製した。骨格として、具体的には負のポアソン比を持つオーセチック構造や、正のポアソン比を持つハニカム構造などを用いた。引張試験結果より、複合材料の強度は格子とマトリックスのポアソン比のミスマッチが大きいほど高くなることが示唆された。偏光顕微鏡観察の結果、本現象は、複合材料の変形時、ポアソン比のミスマッチによりマトリックスが局所的に(巨視的な変形よりも)極めて大きく変形することによって引き起こされていることが示唆された。また、ポアソン比のミスマッチによりマトリックスが(通常では起こりえない)体積変形を強いられることも原因の1つではないかと考えられ、現在検証を進めている。
  • ゲル力学挙動の精密解析による単一高分子鎖の伸長・破断挙動の実験的決定
    日本学術振興会:科学研究費助成事業 若手研究(A)
    研究期間 : 2017年04月 -2021年03月 
    代表者 : 中島 祐
     
    本年度は主に、ゲルの力学物性の精緻な解析による高分子鎖のForce curve抽出法が、前年度に報告したポリエチレングリコール(PEG)のみならず多様な高分子種に対して有効であることを示した。 DNゲルの差分解析法については、網目鎖の分子量が異なるPEGゲル、ランダム共重合により得られたアクリルアミド系ポリマーのPAMPSゲル、多糖であるプルランゲルを第1網目としたDNゲルを合成し、これらDNゲルの応力-歪曲線の差分解析により、多様な化学種の高分子鎖のForce curveを算出した。またゲル膨潤法については、分子量が異なるPEGゲルおよびPAMPSゲルの膨潤度を収縮状態から伸び切り状態まで制御し、その膨潤度と弾性率との関係性から高分子鎖の伸長度と弾性エネルギーとの相関を検討した。いずれの高分子種・解析法においても、得られた高分子鎖の力学特性はAFMによるForce curve測定から得られたものとほぼ一致していた。特にプルランの場合は、そのForce curve中に延伸に伴う環の配座変化に対応する特徴的な挙動が確認された。これらのことから、DNゲルの解析から多様な高分子鎖のForce curveが抽出できることが現象論的に明らかとなった。さらにPEGゲルについて、ゲル膨潤法(三軸延伸)で得られた弾性エネルギーを基に、PEGゲルの一軸延伸に伴う応力-歪曲線の計算を試みたところ、極めて高い精度で実験値と予測値の一致が見られた。ここから、本研究で得られた成果は、多様な高分子ゴム様材料の物性予測にも有用であることが示唆された。 加えて本年度は、DNゲルの差分解析法に関連して、DNゲル延伸時に内部で高分子鎖が極度に伸長されて切断すること、また高分子の切断は化学反応を誘起し得ることに着目し、力学負荷に伴って強度やサイズ、機能が向上する自己成長DNゲルを創製することが出来た。
  • 日本学術振興会:科学研究費助成事業 若手研究(B)
    研究期間 : 2014年04月 -2017年03月 
    代表者 : 中島 祐
     
    ダブルネットワーク(DN)ゲルは、脆い第1網目ゲルとよく伸びる第2網目ゲルとの複合により得られる、極めて丈夫なゲル材料である。本研究では、DNゲルの原理をゴム材料(エラストマー)に適用し、2重網目構造を有する丈夫なエラストマーの創製を試みた。脆い第1網目構造をうまく設計することにより、高い強度、硬さ、伸張性を併せ持つ丈夫なDNエラストマーの創製に成功した。また、植物に含まれるセルロースを第1網目に用いることで、丈夫で環境に優しく、受けたダメージを回復できるDNエラストマーも創製した。
  • 日本学術振興会:科学研究費助成事業 基盤研究(S)
    研究期間 : 2012年05月 -2017年03月 
    代表者 : グン 剣萍, 黒川 孝幸, 中島 祐, 野々山 貴行, 孫 桃林
     
    本研究では、我々が近年提唱した「壊れやすい結合を柔軟なゲルに導入することで強靭化する」という全く新しい「犠牲結合原理」の実証とそれに伴う強靭な機能性ゲル材料の創製を目的とした。壊れやすい結合として共有結合、イオン結合、疎溶媒結合などをゲルに導入した結果、化学種・犠牲結合種のバリエーションを有する一連の強靭ゲルの合成に成功し、本原理がゲルの強靭化に普遍的に適用できることを明らかにした。また導入した犠牲結合の化学種に応じて自己修復性、異方性、構造色などを強靭ゲルに付与することに成功し、犠牲結合原理が多様な機能性ゲルの強靭化に有効であることを示した。
  • 高分子ステント法による、超高強度ダブルネットワークゲルの高強度化手法の一般化
    日本学術振興会:科学研究費助成事業 特別研究員奨励費
    研究期間 : 2010年 -2011年 
    代表者 : 中島 祐
     
    昨年度は本分子ステント法の基礎技術を確立し、あらゆる親水性ポリマーから高強度St-DNゲルが創成可能であることを示した。そこで本年度は、本方法を様々な系へと拡張し、新規機能性高強度ゲルの開発を目指した。最初に、疎水性高分子を1st networkとした高強度ハイドロゲルの創製を行った。本ゲルは、一般的なDNゲルと同様に高い強度を示した他、ハイドロゲルでありながら水に対する高い接触角(80°)を示した。次に、配向高分子フィルムを作製し、これを1st networkに用いることで、物性に異方性のあるSt-DNゲルを合成した。本ゲルは、配向フィルムの構造を反映し、一軸に膨潤する、一方向のみに引き裂き可能などの興味深い新規物性を示した。以上より、疎水性高分子を基にした新規機能性DNゲルの開発に成功した。本結果は、DNゲルの高強度化手法を更に拡張し、従来は実現できなかった機能を発現させたという点で画期的である。また、ステントによるゲル膨潤挙動の理論的な考察を行った。中性ゲルに強電解質高分子(ステント)を導入すると、ステントの持つ高い浸透圧のためにゲルは膨潤する。ステント濃度が0.5Mに達するまでは、ゲルの膨潤挙動は一般的なゲル膨潤理論で説明可能であった。一方、ステント濃度が0.5M以上になると、ゲルの実際の膨潤度は理論値を下回った。本現象は、ステント濃度が大きい時、1st networkゲルの分子鎖の伸び切りが起こっていることを示している。また、本ゲルを基にSt-DNゲルを合成したところ、ステント濃度が0.5M以下の場合、ゲルの力学強度はステント濃度の増加に伴って大きくなるが、0.5M以上ではほぼ同じであった。ここから、St-DNゲルは1st networkが伸び切っているときに高強度化されることが示唆された。以上の成果を基に、現在4編の論文を投稿、あるいは執筆中である。

教育活動情報

主要な担当授業

  • ソフトマター物理学特論
    開講年度 : 2019年
    課程区分 : 修士課程
    開講学部 : 生命科学院
    キーワード : ソフトマター、ソフト界面、濡れ、エマルジョン、泡、変形、応力、ゴム弾性、破壊
  • ソフトマター科学特論
    開講年度 : 2019年
    課程区分 : 修士課程
    開講学部 : 生命科学院
    キーワード : ソフトマター、ソフト界面、濡れ、エマルジョン、泡、変形、応力、ゴム弾性、破壊
  • 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 : 2019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 : soft matter, soft interface, wetting, emusion, foam, deformation, stress, rubber elasticity, fracture
  • 生体高分子学実験Ⅰ
    開講年度 : 2019年
    課程区分 : 学士課程
    開講学部 : 理学部
    キーワード : 物理学実験,化学分析実験,有機合成実験,生化学実験, 分子生物学実験,細胞生物学実験, 生物物理学実験
  • 高分子機能学基礎実験
    開講年度 : 2019年
    課程区分 : 学士課程
    開講学部 : 理学部
    キーワード : 基礎実験手法、物理学実験、化学分析実験、有機合成実験、生化学実験、安全教育、法令
  • 実験生物科学
    開講年度 : 2019年
    課程区分 : 学士課程
    開講学部 : 理学部
    キーワード : 遺伝子解析法, タンパク質解析法, 細胞解析法, 個体解析法, 顕微観察法
  • 化学Ⅰ
    開講年度 : 2019年
    課程区分 : 学士課程
    開講学部 : 全学教育
    キーワード : 原子の構造、原子軌道、化学結合、混成軌道、物質の三態、電解質溶液


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