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Kazutoshi Haraguchi - One of the best experts on this subject based on the ideXlab platform.
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instant strong adhesive behavior of Nanocomposite Gels toward hydrophilic porous materials
Langmuir, 2018Co-Authors: Kazutoshi Haraguchi, Shoichi Shimizu, Satoshi TanakaAbstract:We investigated the adhesion behavior of Nanocomposite hydroGels (NC Gels), consisting of unique organic (polymer)–inorganic (clay) network structures, toward inorganic and organic materials. The NC Gels exhibit instant and strong adhesion to inorganic and organic substrates with hydrophilic porous surfaces. The NC Gels instantly adhere to hydrophilic porous substrates (e.g., unglazed ceramic surfaces and polymer membranes) through simple light contact. In addition, a small piece of NC gel effectively joined two substrate samples (e.g., concrete blocks and bricks) through lamination of the interposing NC gel. The resulting conjoined materials were unable to be separated at the gel–substrate interface; rather, the gel itself fractured upon separation, which indicates that the adhesive strength at the interface is greater than the tensile strength of the NC gel. With the exception of NC Gels with very high clay concentrations (Cclay’s), instant strong adhesion and cohesive failure by subsequent stretching w...
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Nanocomposite Gels by initiator free photopolymerization role of plasma treated clay in the synthesis and network formation
ACS Applied Nano Materials, 2018Co-Authors: Kazutoshi Haraguchi, Tetsuo Takada, Ryosuke HaraguchiAbstract:Nanocomposite hydroGels (NC Gels) composed of polymer–clay networks are successfully synthesized via initiator-free (IF) photopolymerization in aqueous media using plasma-treated clay. IF-NC Gels with a high tensile strength, strain at break, and thermoresponsiveness, which are almost identical to those of NC Gels prepared by redox and photoinitiator methods, are obtained by optimizing the plasma-treatment conditions and exfoliation in water. The clay nanosheets play important roles as initiators, multifunctional cross-linkers, and auxiliary agents for facilitating in situ free-radical polymerization toward IF-NC Gels. The mechanism for the formation of the polymer–clay network in the IF-NC Gels is clarified through Fourier transform infrared and electron spin resonance studies and involves the formation of hydroperoxides and radicals on the clay surface by plasma treatment and subsequent UV irradiation, respectively, and through designed free-radical polymerization experiments in the presence or absence ...
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uniaxial and plane orientations of clay platelets in Nanocomposite Gels with different compositions during stretching and recovery
Polymer, 2017Co-Authors: Kazutoshi Haraguchi, Kazutaka Murata, Yuji KimuraAbstract:Abstract Changes in the birefringence (ΔnNC) of Nanocomposite (NC) Gels upon stretching and recovery were investigated for Gels comprising a poly(N-isopropylacrylamide)−clay network structure. Irrespective of the composition of the NC Gels, a change in the birefringence appeared upon stretching; ΔnNC varied greatly depending on the clay and water contents (Cclay and Cw, respectively) of the Gels and the stretching ratio. The NC Gels with low Cclay gave rise to unique ΔnNC vs. strain curves with a maximum ΔnNC. For samples with higher Cclay, the variation of ΔnNCs observed in the edge- and through-directions, which is attributed to plane-orientation of the clay platelets, increased with increasing Cclay. This was confirmed by scanning electron microscopy observation, and the percentage plane-orientation was evaluated from the ΔnNC data. On recovery of the strain, the plane-oriented clay platelets underwent minimal reversion to the original state, although most of the PNIPA chains reverted to the random conformation. The effects of Cw on the ΔnNC–strain curves were also clarified.
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changes in the properties and self healing behaviors of zwitterionic Nanocomposite Gels across their ucst transition
Macromolecular Symposia, 2015Co-Authors: Kazutoshi Haraguchi, Jinyan NingAbstract:Summary Characteristic properties of zwitterionic Nanocomposite (NC) Gels consisting of a sulfobetaine copolymer and inorganic clay were investigated. The zwitterionic NC Gels were synthesized with different ratios of monomer (x) and clay content (n) by the in situ free-radical polymerization of two monomers, a sulfobetaine monomer (A3) and acrylamide derivative (D), in the presence of exfoliated clay in aqueous media. The resulting zwitterionic A3Dx-NCn Gels were all structurally uniform and mechanically tough because of the polymer–clay network. A3Dx-NCn Gels exhibited a thermoresponsive phase transition with an upper critical solution temperature (UCST) for x ≤ 10 and n ≤ 5. The changes in the property of the A3D10-NC3 gel across the UCST transition were elucidated in terms of optical transmittance, gel volume, dynamic viscoelasticity, and tensile mechanical properties, in addition to the change in self-healing behavior.
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swelling deswelling behavior of zwitterionic Nanocomposite Gels consisting of sulfobetaine polymer clay networks
European Polymer Journal, 2015Co-Authors: Kazutoshi Haraguchi, Jinyan NingAbstract:Abstract The swelling and thermosensitive behaviors of zwitterionic Nanocomposite Gels (Zw-NC Gels) consisting of sulfobetaine polymer–exfoliated clay networks were investigated in water and aqueous NaCl solutions and compared with those of physically and chemically crosslinked zwitterionic Gels and non-zwitterionic NC Gels. Zw-NC Gels showed different swelling behavior that was strongly dependent on the salt concentration (CNaCl), clay concentration (Cclay), and temperature. In water, characteristic swelling-to-deswelling behavior and an abnormal increase in the degree of swelling (DS) with increasing Cclay (∝ crosslink density) were observed. These behaviors were in stark contrast to those obtained with other types of zwitterionic Gels. In NaCl solutions, spontaneous deswelling disappeared within small CNaCl, and above the critical point (0.01 M), the DS increased with CNaCl via an anti-polyelectrolyte effect of the zwitterions and decreased with increasing Cclay. The transparency also changed depending on the CNaCl, Cclay, swelling time, and thermosensitivity of the sulfobetaine polymer. These swelling behaviors and transparency changes of Zw-NC Gels were explained by the combined effects of the zwitterionic polymers (anti-polyelectrolyte), ionic clay (polyelectrolyte), and clay as a crosslinker.
Mitsuhiro Shibayama - One of the best experts on this subject based on the ideXlab platform.
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stress relaxation and hysteresis of Nanocomposite gel investigated by saxs and sans measurement
Polymer, 2012Co-Authors: Toshihiko Nishida, Kazutoshi Haraguchi, Akira Obayashi, Mitsuhiro ShibayamaAbstract:Abstract The stress relaxation phenomena of Nanocomposite gel (NC Gels) after uniaxial elongation was investigated by time-resolved small-angle scattering techniques of neutrons and X-rays. Nanocomposite Gels consist of clay platelets and poly(N-isopropylacrylamide). It was found that clay oriented instantly and polymer chains were elongated along the stretching direction by elongation, followed by gradual process of peeling-off of adsorbed polymer chains on the clay platelets. When the specimen was held in the deformed state, stress relaxation was observed. This was mainly ascribed to peeling-off of polymer chains. When the strain of the specimen was removed, the polymer chains tended to be adsorbed again to the surface of the clay platelets. The deformation mechanism of NC Gels is discussed on the emphasis of the peeling-off and peeling-on process of polymer chains.
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deformation mechanism of Nanocomposite Gels studied by contrast variation small angle neutron scattering
Physical Review E, 2009Co-Authors: Toshihiko Nishida, Kazutoshi Haraguchi, Hitoshi Endo, Noboru Osaka, Mitsuhiro ShibayamaAbstract:Contrast-variation small-angle neutron scattering (CV-SANS) was applied to investigate the deformation mechanism of high-performance Nanocomposite polymer hydroGels (NC Gels) consisting of polymer chains and inorganic clay platelets. Anisotropic SANS functions were obtained at various stretching ratios, $\ensuremath{\lambda}$'s up to $\ensuremath{\lambda}=9$ and were decomposed to three partial structure factors, ${S}_{ij}({Q}_{\ensuremath{\parallel}},{Q}_{\ensuremath{\perp}})$. Here, the subscripts $i$ and $j$ denote the polymer $(P)$ or clay $(C)$ and ${Q}_{\ensuremath{\parallel}}$ and ${Q}_{\ensuremath{\perp}}$ are the magnitude of the scattering vectors along and perpendicular to the stretching directions, respectively. ${S}_{CC}({Q}_{\ensuremath{\parallel}},{Q}_{\ensuremath{\perp}})$ and ${S}_{PP}({Q}_{\ensuremath{\parallel}},{Q}_{\ensuremath{\perp}})$ suggested that the orientation of clay platelets saturated by $\ensuremath{\lambda}\ensuremath{\approx}3$, while the polymer chain stretching continued by further stretching. On the other hand, ${S}_{CP}({Q}_{\ensuremath{\parallel}},{Q}_{\ensuremath{\perp}})$, only available by CV-SANS, indicated the presence of a polymer-enriched layer adsorbed to clay surface, which are responsible for large extensibility of NC Gels over 1000% strain and large toughness exceeding 780 kPa.
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Microphase separation in Nanocomposite Gels.
Physical Review E, 2009Co-Authors: Noboru Osaka, Kazutoshi Haraguchi, Hitoshi Endo, Toshihiko Nishida, Takuya Suzuki, Mitsuhiro ShibayamaAbstract:Microphase separation in poly(N-isopropylacrylamide)(PNIPA)-clay Nanocomposite hydroGels (NC Gels) is investigated by means of contrast-variation small-angle neutron scattering (CV-SANS) and dynamic light scattering (DLS). By using CV-SANS, it is revealed that microphase separation occurs in NC Gels above the lower-critical solution temperature (LCST) of PNIPA aqueous solutions. The observed partial scattering functions show that only the spatial distribution of PNIPA chains is highly distorted by microphase separation and PNIPA chains are preferentially adsorbed on the clay surfaces, where the PNIPA-rich phase forms nanoscaled bicontinuous structure mediated by the clay particles. Additional DLS measurements for dilute solutions with PNIPA and/or the clay nanoparticles confirm that aggregation of PNIPA above the LCST is dramatically suppressed by addition of clay particles. Based on these observations, we conclude that strong affinity between the polymer and clay has a significant effect on the phase separation in NC Gels and allows one to tune the length scale of the phase separation phenomenon by clay concentration.
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Structure of Nanocomposite Hydrogel Investigated by Means of Contrast Variation Small-Angle Neutron Scattering
Macromolecules, 2008Co-Authors: Hitoshi Endo, Kazutoshi Haraguchi, Sho Miyazaki, Mitsuhiro ShibayamaAbstract:The structure of poly(N-isopropylacrylamide)−clay Nanocomposite Gels (NC gel) is investigated. The sophisticated contrast variation small-angle neutron scattering technique leads to obtain the partial scattering functions of each component quantitatively. The extracted partial scattering functions of clay, polymer, and the polymer−clay cross-term are analyzed in detail, and the selective interaction between clay and polymer is revealed. On the basis of these structural observations, it is confirmed that the clay nanoparticles serve as 2-dimensional cross-linkers.
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Deformation Studies on Polymer-Clay Nanocomposite Gels
Macromolecular Symposia, 2007Co-Authors: Mitsuhiro Shibayama, Sho Miyazaki, Hitoshi Endo, Takeshi Karino, Kazutoshi HaraguchiAbstract:Summary: The polymer-clay Nanocomposite Gels (NC Gels), developed by Haraguchi et al. (Adv. Mater., 2001), exhibit extraordinarily high mechanical properties, such as high elongations and high ultimate strengths. In order to understand the origin of these properties, contrast-matched small-angle neutron scattering (SANS) studies were carried out for stretched NC Gels. It was found that (1) the scattering function for NC Gels is simply given by a Lorentz function, a function for semidilute polymer solutions, without a characteristic cross-link inhomogeneity term for polymer Gels, and (2) the unique mechanical properties are ascribed to its network structure, i.e., long polymer chains connected by “plane” cross-links.
Jinyan Ning - One of the best experts on this subject based on the ideXlab platform.
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changes in the properties and self healing behaviors of zwitterionic Nanocomposite Gels across their ucst transition
Macromolecular Symposia, 2015Co-Authors: Kazutoshi Haraguchi, Jinyan NingAbstract:Summary Characteristic properties of zwitterionic Nanocomposite (NC) Gels consisting of a sulfobetaine copolymer and inorganic clay were investigated. The zwitterionic NC Gels were synthesized with different ratios of monomer (x) and clay content (n) by the in situ free-radical polymerization of two monomers, a sulfobetaine monomer (A3) and acrylamide derivative (D), in the presence of exfoliated clay in aqueous media. The resulting zwitterionic A3Dx-NCn Gels were all structurally uniform and mechanically tough because of the polymer–clay network. A3Dx-NCn Gels exhibited a thermoresponsive phase transition with an upper critical solution temperature (UCST) for x ≤ 10 and n ≤ 5. The changes in the property of the A3D10-NC3 gel across the UCST transition were elucidated in terms of optical transmittance, gel volume, dynamic viscoelasticity, and tensile mechanical properties, in addition to the change in self-healing behavior.
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swelling deswelling behavior of zwitterionic Nanocomposite Gels consisting of sulfobetaine polymer clay networks
European Polymer Journal, 2015Co-Authors: Kazutoshi Haraguchi, Jinyan NingAbstract:Abstract The swelling and thermosensitive behaviors of zwitterionic Nanocomposite Gels (Zw-NC Gels) consisting of sulfobetaine polymer–exfoliated clay networks were investigated in water and aqueous NaCl solutions and compared with those of physically and chemically crosslinked zwitterionic Gels and non-zwitterionic NC Gels. Zw-NC Gels showed different swelling behavior that was strongly dependent on the salt concentration (CNaCl), clay concentration (Cclay), and temperature. In water, characteristic swelling-to-deswelling behavior and an abnormal increase in the degree of swelling (DS) with increasing Cclay (∝ crosslink density) were observed. These behaviors were in stark contrast to those obtained with other types of zwitterionic Gels. In NaCl solutions, spontaneous deswelling disappeared within small CNaCl, and above the critical point (0.01 M), the DS increased with CNaCl via an anti-polyelectrolyte effect of the zwitterions and decreased with increasing Cclay. The transparency also changed depending on the CNaCl, Cclay, swelling time, and thermosensitivity of the sulfobetaine polymer. These swelling behaviors and transparency changes of Zw-NC Gels were explained by the combined effects of the zwitterionic polymers (anti-polyelectrolyte), ionic clay (polyelectrolyte), and clay as a crosslinker.
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Swelling/deswelling behavior of zwitterionic Nanocomposite Gels consisting of sulfobetaine polymer–clay networks
European Polymer Journal, 2015Co-Authors: Kazutoshi Haraguchi, Jinyan NingAbstract:Abstract The swelling and thermosensitive behaviors of zwitterionic Nanocomposite Gels (Zw-NC Gels) consisting of sulfobetaine polymer–exfoliated clay networks were investigated in water and aqueous NaCl solutions and compared with those of physically and chemically crosslinked zwitterionic Gels and non-zwitterionic NC Gels. Zw-NC Gels showed different swelling behavior that was strongly dependent on the salt concentration (CNaCl), clay concentration (Cclay), and temperature. In water, characteristic swelling-to-deswelling behavior and an abnormal increase in the degree of swelling (DS) with increasing Cclay (∝ crosslink density) were observed. These behaviors were in stark contrast to those obtained with other types of zwitterionic Gels. In NaCl solutions, spontaneous deswelling disappeared within small CNaCl, and above the critical point (0.01 M), the DS increased with CNaCl via an anti-polyelectrolyte effect of the zwitterions and decreased with increasing Cclay. The transparency also changed depending on the CNaCl, Cclay, swelling time, and thermosensitivity of the sulfobetaine polymer. These swelling behaviors and transparency changes of Zw-NC Gels were explained by the combined effects of the zwitterionic polymers (anti-polyelectrolyte), ionic clay (polyelectrolyte), and clay as a crosslinker.
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synthesis of highly stretchable mechanically tough zwitterionic sulfobetaine Nanocomposite Gels with controlled thermosensitivities
Macromolecules, 2013Co-Authors: Jinyan Ning, Kazutoshi HaraguchiAbstract:Novel Nanocomposite (NC) Gels with zwitterionic characteristics were prepared by in situ free-radical polymerization of sulfobetaine monomers in the presence of exfoliated clay platelets in aqueous media. Two specific sulfobetaine monomers, N,N-dimethyl(acrylamidopropyl)ammonium propanesulfonate and butanesulfonate, were selected on the basis of the interactions between the monomers and clay, which result in uniform aqueous solutions of low viscosity and gel formation without using an organic cross-linker. The resulting NC Gels with polymer–clay network structures were insoluble in NaCl solution or hot water, unlike conventional physically cross-linked Gels. Also, NC Gels with high mechanical properties and well-controlled thermosensitivities were effectively prepared by copolymerization with a small amount of N,N-dimethylacrylamide. The copolymer NC Gels were uniform and simultaneously showed high stretchability, tough mechanical properties, and well-defined upper critical solution temperature (UCST) pha...
Kazutaka Murata - One of the best experts on this subject based on the ideXlab platform.
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uniaxial and plane orientations of clay platelets in Nanocomposite Gels with different compositions during stretching and recovery
Polymer, 2017Co-Authors: Kazutoshi Haraguchi, Kazutaka Murata, Yuji KimuraAbstract:Abstract Changes in the birefringence (ΔnNC) of Nanocomposite (NC) Gels upon stretching and recovery were investigated for Gels comprising a poly(N-isopropylacrylamide)−clay network structure. Irrespective of the composition of the NC Gels, a change in the birefringence appeared upon stretching; ΔnNC varied greatly depending on the clay and water contents (Cclay and Cw, respectively) of the Gels and the stretching ratio. The NC Gels with low Cclay gave rise to unique ΔnNC vs. strain curves with a maximum ΔnNC. For samples with higher Cclay, the variation of ΔnNCs observed in the edge- and through-directions, which is attributed to plane-orientation of the clay platelets, increased with increasing Cclay. This was confirmed by scanning electron microscopy observation, and the percentage plane-orientation was evaluated from the ΔnNC data. On recovery of the strain, the plane-oriented clay platelets underwent minimal reversion to the original state, although most of the PNIPA chains reverted to the random conformation. The effects of Cw on the ΔnNC–strain curves were also clarified.
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Stimuli-Responsive Properties of Nanocomposite Gels Comprising (2-methoxyethylacrylate-co-N,N-dimethylacrylamide) Copolymer-Clay Networks
Macromolecular Symposia, 2013Co-Authors: Kazutoshi Haraguchi, Kazutaka Murata, Toru TakehisaAbstract:Summary Stimuli-responsive properties of Nanocomposite Gels (MD–NC Gels) consisting of (2-methoxyethylacrylate-co-N,N-dimethylacrylamide) copolymer and inorganic clay were investigated. The MDx–NCn Gels were synthesized with different ratios of monomer (x) and clay content (n) by in situ free-radical polymerization of two monomers in the presence of exfoliated clay in aqueous media. The resulting MDx–NCn Gels were always uniform, but the network structure (or clay morphology) and the mechanical and swelling properties were largely dependent on the ratio of x and n. Also, well-defined stimuli-responsive properties such as changes in transparency and gel volume by altering the temperature and salt concentration were observed in the MDx–NCn Gels, particularly with intermediate x (e.g., 10–50) and relatively small n (e.g., 2–5). Further, the reversible change in the gel size and the stress generation therefrom were observed in repeated runs. In addition, thermo-responsive release of drugs (or chemicals) from MDx–NCn Gels was observed.
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Proliferation and harvest of human mesenchymal stem cells using new thermoresponsive Nanocomposite Gels
Journal of biomedical materials research. Part A, 2012Co-Authors: Noriko Kotobuki, Kazutaka Murata, Kazutoshi HaraguchiAbstract:For tissue engineering and regenerative medicine, stem cells should be effectively cultured in vitro. New thermoresponsive Nanocomposite Gels (MD-NC Gels), consisting of inorganic clay (hectorite) and copolymers composed of hydrophobic 2-methoxyethyl acrylate (MEA) and hydrophilic N,N-dimethylacrylamide (DMAA) units, could be applied in cell culture and cell harvesting without trypsinization, specifically using mesenchymal stem cells (MSCs). The composition of the MD-NC gel (the ratio of the two monomer types and the clay content) was found to determine its swelling properties in the culture medium, thermosensitivity, protein adsorption, and cell attachment and proliferation. Various kinds of human cells, including MSCs, osteoblast (HOS) cells, fibroblast (NHDF) cells, and epithelial cells could be effectively cultured on MD-NC Gels. In particular, on an MD10-NC2 gel with relatively low DMAA and clay content, the cells could be harvested by decreasing the temperature, either as a cell sheet (MSCs or NHDF cells) or as a population of suspension cells (HOS cells). Further, it was found that the MD10-NC2 gel is suitable for stem cell differentiation. Because of their thermosensitivity, controllable modulus, and surface properties, MD-NC Gels are promising cell culture substrates useful for tissue engineering and regenerative medicine. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2013.
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stimuli responsive Nanocomposite Gels and soft Nanocomposites consisting of inorganic clays and copolymers with different chemical affinities
Macromolecules, 2012Co-Authors: Kazutoshi Haraguchi, Kazutaka Murata, Toru TakehisaAbstract:A novel series of Nanocomposite hydroGels (MD-NC Gels), consisting of inorganic clay (hectorite) and specific copolymers with different chemical affinities for water, i.e., copolymers composed of hydrophobic (2-methoxyethyl acrylate: MEA) and hydrophilic (N,N-dimethylacrylamide: DMAA) units, were prepared by in situ free-radical polymerization in aqueous media at 20 °C. MD-NC Gels showed outstanding stimuli sensitivities in response to changes in temperature, pH, salt concentration, and solvents in the surrounding aqueous solution as well as excellent, composition-dependent mechanical properties, such as a large elongations at break (≥1000%) and high strengths and moduli. After drying, the Gels were changed into transparent, soft Nanocomposites (MD-NCs) with high mechanical toughness and safety in in vitro cytotoxicity tests. The clay morphology in MD-NCs gradually changed on increasing the molar ratio of DMAA from a clay shell network of 20 nm thickness to a uniform dispersion of exfoliated clay platelet...
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tunable optical and swelling deswelling properties associated with control of the coil to globule transition of poly n isopropylacrylamide in polymer clay Nanocomposite Gels
Macromolecules, 2007Co-Authors: Kazutoshi Haraguchi, Liyuan Song, Huanjun Li, Kazutaka MurataAbstract:Polymer−clay Nanocomposite Gels (NC Gels) consisting of poly(N-isopropylacrylamide) (PNIPA) and inorganic clay (hectorite) were investigated in terms of their optical and swelling/deswelling properties. Depending on the clay concentration (Cclay), NC Gels exhibit unique changes in optical transmittance, optical anisotropy, and swelling/deswelling behaviors, all of which were distinct from those of chemically cross-linked hydroGels (OR Gels). The optical transparency and its temperature-induced change differed greatly between NC and OR Gels. The decrease in transmittance associated with the coil-to-globule transition of PNIPA occurred at higher temperatures than the normal transition temperature in NC Gels as the clay concentration increased. On the assumption of the uniform and random dispersion of exfoliated clay platelets, the critical Cclay (C*clay) for spontaneous clay aggregation (layer stacking) in NC Gels was calculated to be 10 × 10-2 mol/L H2O. C*clay was consistent with the experimental results,...
Liyuan Song - One of the best experts on this subject based on the ideXlab platform.
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Temperature- and pH-Sensitive Nanocomposite Gels with Semi-Interpenetrating Organic/Inorganic Networks
Macromolecular Chemistry and Physics, 2008Co-Authors: Liyuan Song, Meifang Zhu, Yanmo Chen, Kazutoshi HaraguchiAbstract:An intelligent Nanocomposite hydrogel with a semi-interpenetrating organic/inorganic network was synthesized through in situ free-radical polymerization of NIPA in the presence of an inorganic clay and linear PAA. The resulting semi-interpenetrating Nanocomposite Gels (sI-NC Gels) showed mechanical and swelling/deswelling properties greatly superior to those of other PNIPA/PAA hydroGels. The sI-NC Gels repeatedly changed their swelling behavior in response to both temperature and pH while retaining their remarkable mechanical properties. The structure and homogeneity of these networks were studied and related to the properties of sI-NC Gels and the hydrogen bonding interactions among the constituents.
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temperature and ph sensitive Nanocomposite Gels with semi interpenetrating organic inorganic networks
Macromolecular Chemistry and Physics, 2008Co-Authors: Liyuan Song, Meifang Zhu, Yanmo Chen, Kazutoshi HaraguchiAbstract:An intelligent Nanocomposite hydrogel with a semi-interpenetrating organic/inorganic network was synthesized through in situ free-radical polymerization of NIPA in the presence of an inorganic clay and linear PAA. The resulting semi-interpenetrating Nanocomposite Gels (sI-NC Gels) showed mechanical and swelling/deswelling properties greatly superior to those of other PNIPA/PAA hydroGels. The sI-NC Gels repeatedly changed their swelling behavior in response to both temperature and pH while retaining their remarkable mechanical properties. The structure and homogeneity of these networks were studied and related to the properties of sI-NC Gels and the hydrogen bonding interactions among the constituents.
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the unique optical and physical properties of soft transparent stimulus sensitive Nanocomposite Gels
Liquid Crystals, 2007Co-Authors: Kazutoshi Haraguchi, Liyuan SongAbstract:A new type of polymer hydrogel with a unique organic (polymer)/inorganic (clay) network structure has been synthesized by the in-situ free-radical polymerization of N-isopropyl acrylamide (NIPA) in the presence of exfoliated clay platelets in an aqueous medium. The resulting Nanocomposite hydroGels (NC Gels) consisting of PNIPA and clay (hectorite) exhibit extraordinary optical, mechanical and swelling properties. NC Gels also show a clear phase transition due to the coil-to-globule transition of the PNIPA chains. It was observed that the phase-transition temperature (lower critical solution temperature: LCST), defined as the onset temperature of a steep transmittance drop, shifts to a lower or higher temperature than that of pure water (≅ 34 °C) when conditions are altered. When an inorganic salt, such as NaCl, CaCl 2 and AlCl 3 , was added to the surrounding water, the LCST of the NC Gels generally shifted to a lower temperature, in a manner almost inversely proportional to the salt concentration. On the other hand, when the NC Gels adsorbed cationic surfactant, e.g. hexadecyl trimethyl ammonium chloride, the LCST shifted toward a higher temperature, although the shift and its profile strongly depended on the adsorption conditions, such as the surfactant concentration and the adsorption time. Consequently, non-thermo-sensitive NC gel was obtained by using a surfactant aqueous solution with a concentration higher than the critical micelle concentration.
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tunable optical and swelling deswelling properties associated with control of the coil to globule transition of poly n isopropylacrylamide in polymer clay Nanocomposite Gels
Macromolecules, 2007Co-Authors: Kazutoshi Haraguchi, Liyuan Song, Huanjun Li, Kazutaka MurataAbstract:Polymer−clay Nanocomposite Gels (NC Gels) consisting of poly(N-isopropylacrylamide) (PNIPA) and inorganic clay (hectorite) were investigated in terms of their optical and swelling/deswelling properties. Depending on the clay concentration (Cclay), NC Gels exhibit unique changes in optical transmittance, optical anisotropy, and swelling/deswelling behaviors, all of which were distinct from those of chemically cross-linked hydroGels (OR Gels). The optical transparency and its temperature-induced change differed greatly between NC and OR Gels. The decrease in transmittance associated with the coil-to-globule transition of PNIPA occurred at higher temperatures than the normal transition temperature in NC Gels as the clay concentration increased. On the assumption of the uniform and random dispersion of exfoliated clay platelets, the critical Cclay (C*clay) for spontaneous clay aggregation (layer stacking) in NC Gels was calculated to be 10 × 10-2 mol/L H2O. C*clay was consistent with the experimental results,...
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Tunable Optical and Swelling/Deswelling Properties Associated with Control of the Coil-to-Globule Transition of Poly(N-isopropylacrylamide) in Polymer−Clay Nanocomposite Gels
Macromolecules, 2007Co-Authors: Kazutoshi Haraguchi, Liyuan Song, Kazutaka MurataAbstract:Polymer−clay Nanocomposite Gels (NC Gels) consisting of poly(N-isopropylacrylamide) (PNIPA) and inorganic clay (hectorite) were investigated in terms of their optical and swelling/deswelling properties. Depending on the clay concentration (Cclay), NC Gels exhibit unique changes in optical transmittance, optical anisotropy, and swelling/deswelling behaviors, all of which were distinct from those of chemically cross-linked hydroGels (OR Gels). The optical transparency and its temperature-induced change differed greatly between NC and OR Gels. The decrease in transmittance associated with the coil-to-globule transition of PNIPA occurred at higher temperatures than the normal transition temperature in NC Gels as the clay concentration increased. On the assumption of the uniform and random dispersion of exfoliated clay platelets, the critical Cclay (C*clay) for spontaneous clay aggregation (layer stacking) in NC Gels was calculated to be 10 × 10-2 mol/L H2O. C*clay was consistent with the experimental results,...
