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Akira Isogai - One of the best experts on this subject based on the ideXlab platform.
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dual functions of tempo Oxidized Cellulose nanofibers in oil in water emulsions a pickering emulsifier and a unique dispersion stabilizer
Langmuir, 2019Co-Authors: Shuji Fujisawa, Tsuguyuki Saito, Kenichi Yamane, Katsushi Kuroda, Akira IsogaiAbstract:The emulsifying and dispersing mechanisms of oil-in-water emulsions stabilized by 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO)-Oxidized Cellulose nanofibers (CNFs) have been investigated. The emulsi...
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properties of poly acrylamide tempo Oxidized Cellulose nanofibril composite films
Cellulose, 2014Co-Authors: Takanori Kurihara, Akira IsogaiAbstract:Self-standing composite films consisting of 2,2,6,6-tetramethylpiperidine-1-oxyl-Oxidized Cellulose nanofibril (TOCN) and anionic poly(acrylamide) (PAM) in various weight ratios were prepared by casting and drying of homogeneous mixtures of aqueous TOCN dispersion and PAM solution. PAM/TOCN composite films consisting of 25 % PAM and 75 % TOCN had clearly higher Young’s modulus (13.9 GPa) and tensile strength (266 MPa) than 100 % TOCN film (10.8 GPa and 223 MPa, respectively) or 100 % PAM film (4.9 GPa and 78 MPa, respectively), showing that PAM molecules have mechanical reinforcement ability in TOCN matrix. Some attractive interactions are likely formed between TOCN element surfaces and PAM molecules. In contrast, no such mechanical improvements were observed for poly(vinyl alcohol)/TOCN or Oxidized starch/TOCN composite films prepared as references. Moreover, the mechanical properties of the PAM/TOCN composite films were further improved by controlling molecular mass and branching degree of the PAM. The high optical transparency and low coefficient of thermal expansion of the 100 % TOCN film were mostly maintained in the TOCN composite film containing 25 % PAM.
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tempo Oxidized Cellulose hydrogel as a high capacity and reusable heavy metal ion adsorbent
Journal of Hazardous Materials, 2013Co-Authors: Noriyuki Isobe, Tsuguyuki Saito, Satoshi Kimura, Masahisa Wada, Xiaoxia Chen, Akira IsogaiAbstract:Abstract Nitroxy radical catalyzed oxidation with hypochlorite/bromide (TEMPO-mediated oxidation) was performed on a Cellulose hydrogel prepared using LiOH/urea solvent. TEMPO oxidation successfully introduced carboxyl groups onto the surface of the Cellulose hydrogel with retention of the gel structure and its nanoporous property. The equilibrium measurement of Cu 2+ adsorption showed favorable interaction with Cu 2+ and high maximum adsorption capacity. In addition, over 98% of the adsorbed Cu 2+ was recovered using acid treatment, and the subsequent washing allowed the TEMPO-Oxidized gels to be used repeatedly. Furthermore, the TEMPO-Oxidized Cellulose hydrogel showed high adsorption capacity for other toxic metal ions such as Zn 2+ , Fe 3+ , Cd 2+ , and Cs + .
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influence of tempo Oxidized Cellulose nanofibril length on film properties
Carbohydrate Polymers, 2013Co-Authors: Hayaka Fukuzumi, Tsuguyuki Saito, Akira IsogaiAbstract:Various mechanical disintegration conditions in water were applied to 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-Oxidized Cellulose to prepare TEMPO-Oxidized Cellulose nanofibrils (TOCNs) of uniform widths ∼4 nm but with three different average lengths, 200, 680, and 1100 nm. The viscosity average degrees of polymerization of the TOCNs were 250, 350, and 400, respectively. Self-standing TOCN and TOCN-coated poly(ethylene terephthalate) (PET) and poly(lactic acid) (PLA) films were prepared, and the optical, mechanical and gas-barrier properties of the films were evaluated in terms of nanofibril length. Only small differences in density, water content, and elastic modulus of the films were observed but TOCN films prepared from longer nanofibrils clearly showed higher tensile strengths, elongations at break and crystallinity indices. The oxygen barrier properties of the TOCN-coated PET and PLA films increased with increasing nanofibril length. In contrast, nanofibril length had almost no influence on water vapor-barrier properties.
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Degradation of TEMPO-Oxidized Cellulose fibers and nanofibrils by crude cellulase
Cellulose, 2013Co-Authors: Ikue Homma, Tsuguyuki Saito, Takuya Isogai, Akira IsogaiAbstract:The biodegradation behavior of 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-Oxidized Cellulose fibers (TOCs) suspended in water and TEMPO-Oxidized Cellulose nanofibrils (TOCNs) dispersed in water by a commercial crude cellulase was studied. Products crude cellulase-treated for 0–7 days were separated into water/ethanol-insoluble and -soluble fractions. Weight recovery ratios and viscosity-average degrees of polymerization of the water/ethanol-insoluble fractions clearly decreased with crude cellulase-treatment time, showing that both TOCs and TOCNs have biodegradability. Water/ethanol-soluble fractions were subjected to size-exclusion chromatography (SEC) with photodiode array (PDA) detection to obtain SEC elution patterns detected by reflective index and UV spectra of each SEC pattern elution slice. SEC–PDA and 13C-NMR analyses showed that glucuronosyl unit-containing molecules present on microfibril surfaces in TOCs and TOCNs were primarily cleaved by hydrolyzing enzymes present as contaminants in the crude cellulase to form glucuronic acid as one of the major water-soluble degradation compounds. After the glucuronosyl units in TOCs and TOCNs were degraded and removed from microfibril surfaces by the hydrolyzing enzymes, Cellulose chains newly exposed on the microfibril surfaces were rapidly hydrolyzed by cellulases predominantly present in the crude cellulase to form cellobiose. Both TOCs and TOCNs having sodium carboxyl groups are thus biodegradable, but TOCN having free carboxyl groups had clearly low biodegradability by the crude cellulase. Thus, biodegradation behavior may be controllable by controlling the structure of carboxyl group counter ions in TOCs and TOCNs.
Tsuguyuki Saito - One of the best experts on this subject based on the ideXlab platform.
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dual functions of tempo Oxidized Cellulose nanofibers in oil in water emulsions a pickering emulsifier and a unique dispersion stabilizer
Langmuir, 2019Co-Authors: Shuji Fujisawa, Tsuguyuki Saito, Kenichi Yamane, Katsushi Kuroda, Akira IsogaiAbstract:The emulsifying and dispersing mechanisms of oil-in-water emulsions stabilized by 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO)-Oxidized Cellulose nanofibers (CNFs) have been investigated. The emulsi...
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tempo Oxidized Cellulose hydrogel as a high capacity and reusable heavy metal ion adsorbent
Journal of Hazardous Materials, 2013Co-Authors: Noriyuki Isobe, Tsuguyuki Saito, Satoshi Kimura, Masahisa Wada, Xiaoxia Chen, Akira IsogaiAbstract:Abstract Nitroxy radical catalyzed oxidation with hypochlorite/bromide (TEMPO-mediated oxidation) was performed on a Cellulose hydrogel prepared using LiOH/urea solvent. TEMPO oxidation successfully introduced carboxyl groups onto the surface of the Cellulose hydrogel with retention of the gel structure and its nanoporous property. The equilibrium measurement of Cu 2+ adsorption showed favorable interaction with Cu 2+ and high maximum adsorption capacity. In addition, over 98% of the adsorbed Cu 2+ was recovered using acid treatment, and the subsequent washing allowed the TEMPO-Oxidized gels to be used repeatedly. Furthermore, the TEMPO-Oxidized Cellulose hydrogel showed high adsorption capacity for other toxic metal ions such as Zn 2+ , Fe 3+ , Cd 2+ , and Cs + .
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influence of tempo Oxidized Cellulose nanofibril length on film properties
Carbohydrate Polymers, 2013Co-Authors: Hayaka Fukuzumi, Tsuguyuki Saito, Akira IsogaiAbstract:Various mechanical disintegration conditions in water were applied to 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-Oxidized Cellulose to prepare TEMPO-Oxidized Cellulose nanofibrils (TOCNs) of uniform widths ∼4 nm but with three different average lengths, 200, 680, and 1100 nm. The viscosity average degrees of polymerization of the TOCNs were 250, 350, and 400, respectively. Self-standing TOCN and TOCN-coated poly(ethylene terephthalate) (PET) and poly(lactic acid) (PLA) films were prepared, and the optical, mechanical and gas-barrier properties of the films were evaluated in terms of nanofibril length. Only small differences in density, water content, and elastic modulus of the films were observed but TOCN films prepared from longer nanofibrils clearly showed higher tensile strengths, elongations at break and crystallinity indices. The oxygen barrier properties of the TOCN-coated PET and PLA films increased with increasing nanofibril length. In contrast, nanofibril length had almost no influence on water vapor-barrier properties.
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Degradation of TEMPO-Oxidized Cellulose fibers and nanofibrils by crude cellulase
Cellulose, 2013Co-Authors: Ikue Homma, Tsuguyuki Saito, Takuya Isogai, Akira IsogaiAbstract:The biodegradation behavior of 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-Oxidized Cellulose fibers (TOCs) suspended in water and TEMPO-Oxidized Cellulose nanofibrils (TOCNs) dispersed in water by a commercial crude cellulase was studied. Products crude cellulase-treated for 0–7 days were separated into water/ethanol-insoluble and -soluble fractions. Weight recovery ratios and viscosity-average degrees of polymerization of the water/ethanol-insoluble fractions clearly decreased with crude cellulase-treatment time, showing that both TOCs and TOCNs have biodegradability. Water/ethanol-soluble fractions were subjected to size-exclusion chromatography (SEC) with photodiode array (PDA) detection to obtain SEC elution patterns detected by reflective index and UV spectra of each SEC pattern elution slice. SEC–PDA and 13C-NMR analyses showed that glucuronosyl unit-containing molecules present on microfibril surfaces in TOCs and TOCNs were primarily cleaved by hydrolyzing enzymes present as contaminants in the crude cellulase to form glucuronic acid as one of the major water-soluble degradation compounds. After the glucuronosyl units in TOCs and TOCNs were degraded and removed from microfibril surfaces by the hydrolyzing enzymes, Cellulose chains newly exposed on the microfibril surfaces were rapidly hydrolyzed by cellulases predominantly present in the crude cellulase to form cellobiose. Both TOCs and TOCNs having sodium carboxyl groups are thus biodegradable, but TOCN having free carboxyl groups had clearly low biodegradability by the crude cellulase. Thus, biodegradation behavior may be controllable by controlling the structure of carboxyl group counter ions in TOCs and TOCNs.
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tempo Oxidized Cellulose nanofibril poly vinyl alcohol composite drawn fibers
Polymer, 2013Co-Authors: Ryokei Endo, Tsuguyuki Saito, Akira IsogaiAbstract:Abstract PVA/TOCN composite fiber with a weight ratio of 100:1 was prepared from a mixture of aqueous poly(vinyl alcohol) (PVA) solution and 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO)-Oxidized Cellulose nanofibril (TOCN) dispersion using spinning, drawing, and drying processes. The as-spun PVA/TOCN composite fiber was further drawn, up to a draw ratio of 20 by heating at up to 230 °C. The maximum tensile modulus of the PVA/TOCN composite drawn fiber reached 57 GPa, remarkably higher than that of commercial PVA drawn fibers. Moreover, the PVA/TOCN composite drawn fiber had storage modulus higher than that of the PVA drawn fiber at each temperature in the range from 28 to 239 °C. Structural analyses showed that amorphous PVA regions in the composite drawn fiber were more oriented than those in neat PVA fiber after the addition of the small amount of TOCN used. These results indicate that TOCN elements were individually dispersed in the PVA matrix without aggregation and formed hydrogen bonds with amorphous PVA molecules in the composite drawn fiber.
Hayaka Fukuzumi - One of the best experts on this subject based on the ideXlab platform.
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influence of tempo Oxidized Cellulose nanofibril length on film properties
Carbohydrate Polymers, 2013Co-Authors: Hayaka Fukuzumi, Tsuguyuki Saito, Akira IsogaiAbstract:Various mechanical disintegration conditions in water were applied to 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-Oxidized Cellulose to prepare TEMPO-Oxidized Cellulose nanofibrils (TOCNs) of uniform widths ∼4 nm but with three different average lengths, 200, 680, and 1100 nm. The viscosity average degrees of polymerization of the TOCNs were 250, 350, and 400, respectively. Self-standing TOCN and TOCN-coated poly(ethylene terephthalate) (PET) and poly(lactic acid) (PLA) films were prepared, and the optical, mechanical and gas-barrier properties of the films were evaluated in terms of nanofibril length. Only small differences in density, water content, and elastic modulus of the films were observed but TOCN films prepared from longer nanofibrils clearly showed higher tensile strengths, elongations at break and crystallinity indices. The oxygen barrier properties of the TOCN-coated PET and PLA films increased with increasing nanofibril length. In contrast, nanofibril length had almost no influence on water vapor-barrier properties.
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Influence of TEMPO-Oxidized Cellulose nanofibril length on film properties
Carbohydrate Polymers, 2013Co-Authors: Hayaka Fukuzumi, Tsuguyuki Saito, Akira IsogaiAbstract:Various mechanical disintegration conditions in water were applied to 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-Oxidized Cellulose to prepare TEMPO-Oxidized Cellulose nanofibrils (TOCNs) of uniform widths ∼4 nm but with three different average lengths, 200, 680, and 1100 nm. The viscosity average degrees of polymerization of the TOCNs were 250, 350, and 400, respectively. Self-standing TOCN and TOCN-coated poly(ethylene terephthalate) (PET) and poly(lactic acid) (PLA) films were prepared, and the optical, mechanical and gas-barrier properties of the films were evaluated in terms of nanofibril length. Only small differences in density, water content, and elastic modulus of the films were observed but TOCN films prepared from longer nanofibrils clearly showed higher tensile strengths, elongations at break and crystallinity indices. The oxygen barrier properties of the TOCN-coated PET and PLA films increased with increasing nanofibril length. In contrast, nanofibril length had almost no influence on water vapor-barrier properties. © 2012 Elsevier Ltd.
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TEMPO-Oxidized Cellulose nanofibers
Nanoscale, 2011Co-Authors: Akira Isogai, Tsuguyuki Saito, Hayaka FukuzumiAbstract:Native wood Celluloses can be converted to individual nanofibers 3-4 nm wide that are at least several microns in length, i.e. with aspect ratios>100, by TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-mediated oxidation and successive mild disintegration in water. Preparation methods and fundamental characteristics of TEMPO-Oxidized Cellulose nanofibers (TOCN) are reviewed in this paper. Significant amounts of C6 carboxylate groups are selectively formed on each Cellulose microfibril surface by TEMPO-mediated oxidation without any changes to the original crystallinity (∼74%) or crystal width of wood Celluloses. Electrostatic repulsion and/or osmotic effects working between anionically-charged Cellulose microfibrils, the ζ-potentials of which are approximately -75 mV in water, cause the formation of completely individualized TOCN dispersed in water by gentle mechanical disintegration treatment of TEMPO-Oxidized wood Cellulose fibers. Self-standing TOCN films are transparent and flexible, with high tensile strengths of 200-300 MPa and elastic moduli of 6-7 GPa. Moreover, TOCN-coated poly(lactic acid) films have extremely low oxygen permeability. The new Cellulose-based nanofibers formed by size reduction process of native Cellulose fibers by TEMPO-mediated oxidation have potential application as environmentally friendly and new bio-based nanomaterials in high-tech fields.
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thermal stabilization of tempo Oxidized Cellulose
Polymer Degradation and Stability, 2010Co-Authors: Hayaka Fukuzumi, Yusuke Okita, Tsuguyuki Saito, Akira IsogaiAbstract:Abstract A partially C6-carboxylated Cellulose with carboxylate content of 1.68 mmol/g was prepared by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation of a softwood bleached kraft pulp. Thermogravimetric analyses of the TEMPO-Oxidized Cellulose (TOC) and its related materials were studied to improve thermal stability of the TOC. Thermal decomposition (T d ) points of the TOC with sodium carboxylate groups, alkali-treated TOC with free carboxyl groups of 0.23 mmol/g and the original Cellulose were 222 °C, 264 °C and 275 °C, respectively. Thus, the anhydroglucuronic acid units formed by TEMPO-mediated oxidation of the native wood Cellulose and present in the TOC cause the decrease in T d point by decarbonation during heating process. When carboxyl groups in the TOC were methylated with trimethylsilyl diazomethane (TMSCHN 2 ), the T d point increased from 222 °C to 249 °C, and the peak temperature in its derivative thermogravimetric (DTG) curve increased from 273 °C to 313 °C, which was almost equal to that of the original Cellulose. Thus, the methyl esterification of carboxyl groups in the TOC is effective in improving thermal stability. When sodium ions present in the TOC as counter ions of carboxylate groups were exchanged to some other metal ions, thermal stability was improved to some extent. Especially, when CaCl 2 , Ca(OAc) 2 , Ca(NO 3 ) 2 and CaI 2 solutions were used in the ion-exchange treatments, the peak temperatures in the DTG curves increased to approximately 300 °C. MgCl 2 , NiCl 2 , SrCl 2 and Sr(OAc) 2 solutions were also effective to some extent in increasing the peak temperatures of DTG curves. Thus, thermal stability of the fibrous TOC can be improved to some extent by methyl esterification of the sodium carboxylate groups present in the original TOC with TMSCHN 2 or ion-exchange treatments with some metal salt solutions.
Oyvind Weiby Gregersen - One of the best experts on this subject based on the ideXlab platform.
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tempo Oxidized Cellulose nanofiber films effect of surface morphology on water resistance
Cellulose, 2012Co-Authors: Galina Rodionova, Oyvind Eriksen, Oyvind Weiby GregersenAbstract:2,2,6,6-Tetramethylpiperidine-1-oxyl radical (TEMPO)-Oxidized Cellulose nanofibers were prepared from two kraft pulps (Norway spruce and mixed eucalyptus) using the TEMPO/NaBr/NaClO system at pH 10 and 22 °C. After reaction and mechanical treatment, the TEMPO-Oxidized Celluloses were used for preparation of self-standing films and coatings of laminate films on 50-μm-thick polyethylene terephthalate films. Characterization of the films was performed based on water contact angle measurements, laser profilometry, scanning electron microscopy, and field-emission scanning electron microscopy. The purpose of this study is to understand how the measured contact angles are affected by the film’s physical properties (morphology, thickness, density, and roughness).
Aji P. Mathew - One of the best experts on this subject based on the ideXlab platform.
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Multifunctional materials for environmental applications based on TEMPO-Oxidized Cellulose nanofibers (TOCNF)
2020Co-Authors: Aji P. Mathew, Kristiina OksmanAbstract:Multifunctional materials for environmental applications based on TEMPO-Oxidized Cellulose nanofibers (TOCNF)
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surface adsorption and self assembly of cu ii ions on tempo Oxidized Cellulose nanofibers in aqueous media
Journal of Colloid and Interface Science, 2016Co-Authors: Kristiina Oksman, Aji P. MathewAbstract:TEMPO-mediated Oxidized Cellulose nanofibers (TOCNFs) have shown potential in the bioremediation of metal ions from contaminated water due to their interaction with positively charged metal ions vi ...
