Clay−alcohol−water ternary dispersions were compared with alcohol−water binary mixtures in terms ... more Clay−alcohol−water ternary dispersions were compared with alcohol−water binary mixtures in terms of viscosity and optical absorbance. Aqueous clay dispersions to which lower alcohols (ethanol, 1-propanol, 2-propanol, and tert-butanol) were added exhibited significant viscosity anomalies (maxima) when the alcohol content was 30−55 wt %, as well as optical absorbance anomalies (maxima). The maximum viscosity (η max) depended strongly on the clay content and varied between 300 and 8000 mPa•s, making it remarkably high compared with the viscosity anomalies (2 mPa•s) observed in alcohol−water binary mixtures. The alcohol content at η max decreased as the hydrophobicity of the alcohol increased. The ternary dispersions with viscosity anomalies exhibited thixotropic behaviors. The effects of other hydrophilic solvents (glycols) and other kinds of clays were also clarified. Based on these findings and the average particle size changes, the viscosity anomalies in the ternary dispersions were explained by alcohol-clustering-induced network formation of the clay nanosheets. It was estimated that 0.9, 1.7, and 2.5 H 2 O molecules per alcohol molecule were required to stabilize the ethanol, 2-propanol, and tert-butanol, respectively, in the clay− alcohol−water dispersions.
Exfoliated clay nanosheets (CNSs) of synthetic hectorite (s-hectorite) have been used for synthes... more Exfoliated clay nanosheets (CNSs) of synthetic hectorite (s-hectorite) have been used for synthesizing advanced functional materials and gels that exhibit high transparency, high mechanical toughness, and many unprecedented characteristics like optical anisotropy, cell harvesting, instant strong adhesion, and self-healing. Therefore, it is important to determine the rheological properties of aqueous s-hectorite dispersions in terms of the CNS microstructures formed in the dispersion. Herein, viscosity changes in aqueous dispersions of s-hectorite were determined using a vibration viscometer to measure viscosity under agitated and static conditions. Upon varying the pH and salt concentration, aqueous dispersions of s-hectorite exhibited a maximum viscosity accompanied by gelation. Additionally, the aqueous dispersion with maximum viscosity exhibited large and complex time-dependent viscosity changes in the static state after cessation of stirring. The anomalous viscosity dynamics dep...
International Journal of Materials Science and Applications, 2018
The selective separation of organic electrolytes by neutralization dialysis was investigated with... more The selective separation of organic electrolytes by neutralization dialysis was investigated with two kinds of grafted polyethylene (PE) films prepared through the photografting of 2-(dimethylamino) ethyl methacrylate (DMAEMA) onto the PE films and the subsequent quaternization and through the photografting of glycidyl methacrylate (GMA) and the subsequent sulfonation. The permeation flux of benzoic acid (BA) for the quarternized DMAEMA-grafted PE (PE-g-QPDMAEMA) films increased with an increase in the degree of quaternization, and the BA permeability had the maximum at the initial pH value of the permeate solution of 12.0. On the other hand, the sulfonation offered the phenylalaninol (Phl) permeability of the GMA-grafted PE (PE-g-PGMA) films. The selective separation for the binary BA/Phl or 2,5-dichlorobenzoic acid/Phl systems was successfully achieved by use of a pH difference between the feed and permeate solutions through the PEg -QPDMAEMA and sulfonated PEg -PGMA (PE-g-SPGMA) films. The maximum selective separation was obtained under the conditions that the initial pH values of the permeate solutions through the PEg -QPDMAEMA and PEg -SPGMA films were adjusted to 12.0 and 2.0, respectively. This procedure will be applied to separation and concentration of organic electrolytes and water purification.
Journal of Photopolymer Science and Technology, 2015
In this study, methacrylic acid (MAA) was grafted onto a poly(tetrafluoroethylene) (PTFE) plate b... more In this study, methacrylic acid (MAA) was grafted onto a poly(tetrafluoroethylene) (PTFE) plate by the oxygen plasma treatment and subsequent photografting. The surfaces of the grafted PTFE plates prepared at shorter plasma treatment times and/or at lower monomer concentrations were modified hydrophilic at lower grafted amounts. Water absorptivity of the grafted layer increased with the grafted amount and the grafted layers formed at lower monomer concentrations possessed higher water absorptivity. For grafted PTFE plates prepared at the monomer concentration of 1.5 and 2.0 M after the plasma treatment, the substrate breaking occurred. The grafted amount at substrate breaking decreased with a decrease in the plasma treatment time, indicating that the location of photografting was restricted to the outer surface region at shorter plasma treatment times. It was made clear that the combination of the oxygen plasma treatment with the photografting of MAA was an effective procedure to modify the PTFE surface.
ABSTRACTHalloysite nanotube (HNT), a natural clay, was modified with branched polyethyleneimine (... more ABSTRACTHalloysite nanotube (HNT), a natural clay, was modified with branched polyethyleneimine (PEI) to form PEI‐HNT using epichlorohydrin (ECH) as coupling agent, then protonated with HCl to obtain H‐PEI‐HNTs providing [NH3]+[Cl]− functionality for potential antimicrobial properties. Upon PEI modification, zeta potential value of HNTs was increased to +37.3 mV from −34.5 mV and to +41.1 mV for H‐PEI‐HNTs. Only 1.87 wt % H‐element in HNT was increased to 3.03 wt % upon PEI modification along with newly generated elements of N and C at 2.99 and 9.93 wt %, respectively. Moreover, ionic liquid (IL) forms of HNTs with [NH3]+[N(CN)2]−, [NH3]+[PF6]− and [NH3]+[BF4]− functionality were generated via anion exchange of H‐PEI‐HNTs with sodium dicyanamide (SDC), ammonium hexafluorophosphate (AHFP), and sodium tetrafluoroborate (STFB). The antimicrobial properties of the modified, protonated, and IL forms of HNTs were determined via macro dilution, diffusion and agar screening tests against Es...
In this study, the combined use of chitosan and mushroom tyrosinase was applied to remove 1‐napht... more In this study, the combined use of chitosan and mushroom tyrosinase was applied to remove 1‐naphthol and 2‐naphthol from aqueous solutions. In particular, the process parameters, such as the pH value, temperature, and enzyme dose, were discussed for tyrosinase‐catalyzed quinone oxidation of 1‐naphthol. The optimum conditions of enzymatic quinone oxidation of 1‐naphthol were determined to be pH 8.0 and 40°C. Under the optimum conditions, quinone oxidation of 1‐naphthol increased with an increase in the enzyme dose. Quinone derivatives enzymatically generated were chemisorbed on chitosan bead sand. The initial velocity of enzymatic quinone oxidation increased with an increase in the amount of added chitosan beads, since unfavorable interactions between quinone derivatives and tyrosinase in the solutions were restrained by quinone adsorption. 1‐Naphthol was completely removed for 8 h by quinone adsorption on chitosan beads (0.10 cm3/cm3) at 20 U/cm3. The removal time was shortened by i...
In this study, the combined use of a biopolymer chitosan and an oxidoreductase polyphenol oxidase... more In this study, the combined use of a biopolymer chitosan and an oxidoreductase polyphenol oxidase (PPO) was systematically investigated for removal of bisphenol derivatives from aqueous medium. The process parameters, such as the pH value, temperature, and PPO concentration, were estimated to conduct the enzymatic quinone oxidation of bisphenol derivatives by as little enzyme as possible. Bisphenol derivatives effectively underwent PPO-catalyzed quinone oxidation without H2O2 unlike other oxidoreductases, such as peroxidase and tyrosinase, and the optimum conditions were determined to be pH 7.0 and 40 °C for bisphenol B, bisphenol E, bisphenol O, and bisphenol Z, pH 7.0 and 30 °C for bisphenol C and bisphenol F, and pH 8.0 and 40 °C for bisphenol T. They were completely removed through adsorption of enzymatically generated quinone derivatives on chitosan beads or chitosan powders. Quinone adsorption on chitosan beads or chitosan powders in the heterogeneous system was found to be a ...
Clay−alcohol−water ternary dispersions were compared with alcohol−water binary mixtures in terms ... more Clay−alcohol−water ternary dispersions were compared with alcohol−water binary mixtures in terms of viscosity and optical absorbance. Aqueous clay dispersions to which lower alcohols (ethanol, 1-propanol, 2-propanol, and tert-butanol) were added exhibited significant viscosity anomalies (maxima) when the alcohol content was 30−55 wt %, as well as optical absorbance anomalies (maxima). The maximum viscosity (η max) depended strongly on the clay content and varied between 300 and 8000 mPa•s, making it remarkably high compared with the viscosity anomalies (2 mPa•s) observed in alcohol−water binary mixtures. The alcohol content at η max decreased as the hydrophobicity of the alcohol increased. The ternary dispersions with viscosity anomalies exhibited thixotropic behaviors. The effects of other hydrophilic solvents (glycols) and other kinds of clays were also clarified. Based on these findings and the average particle size changes, the viscosity anomalies in the ternary dispersions were explained by alcohol-clustering-induced network formation of the clay nanosheets. It was estimated that 0.9, 1.7, and 2.5 H 2 O molecules per alcohol molecule were required to stabilize the ethanol, 2-propanol, and tert-butanol, respectively, in the clay− alcohol−water dispersions.
Exfoliated clay nanosheets (CNSs) of synthetic hectorite (s-hectorite) have been used for synthes... more Exfoliated clay nanosheets (CNSs) of synthetic hectorite (s-hectorite) have been used for synthesizing advanced functional materials and gels that exhibit high transparency, high mechanical toughness, and many unprecedented characteristics like optical anisotropy, cell harvesting, instant strong adhesion, and self-healing. Therefore, it is important to determine the rheological properties of aqueous s-hectorite dispersions in terms of the CNS microstructures formed in the dispersion. Herein, viscosity changes in aqueous dispersions of s-hectorite were determined using a vibration viscometer to measure viscosity under agitated and static conditions. Upon varying the pH and salt concentration, aqueous dispersions of s-hectorite exhibited a maximum viscosity accompanied by gelation. Additionally, the aqueous dispersion with maximum viscosity exhibited large and complex time-dependent viscosity changes in the static state after cessation of stirring. The anomalous viscosity dynamics dep...
International Journal of Materials Science and Applications, 2018
The selective separation of organic electrolytes by neutralization dialysis was investigated with... more The selective separation of organic electrolytes by neutralization dialysis was investigated with two kinds of grafted polyethylene (PE) films prepared through the photografting of 2-(dimethylamino) ethyl methacrylate (DMAEMA) onto the PE films and the subsequent quaternization and through the photografting of glycidyl methacrylate (GMA) and the subsequent sulfonation. The permeation flux of benzoic acid (BA) for the quarternized DMAEMA-grafted PE (PE-g-QPDMAEMA) films increased with an increase in the degree of quaternization, and the BA permeability had the maximum at the initial pH value of the permeate solution of 12.0. On the other hand, the sulfonation offered the phenylalaninol (Phl) permeability of the GMA-grafted PE (PE-g-PGMA) films. The selective separation for the binary BA/Phl or 2,5-dichlorobenzoic acid/Phl systems was successfully achieved by use of a pH difference between the feed and permeate solutions through the PEg -QPDMAEMA and sulfonated PEg -PGMA (PE-g-SPGMA) films. The maximum selective separation was obtained under the conditions that the initial pH values of the permeate solutions through the PEg -QPDMAEMA and PEg -SPGMA films were adjusted to 12.0 and 2.0, respectively. This procedure will be applied to separation and concentration of organic electrolytes and water purification.
Journal of Photopolymer Science and Technology, 2015
In this study, methacrylic acid (MAA) was grafted onto a poly(tetrafluoroethylene) (PTFE) plate b... more In this study, methacrylic acid (MAA) was grafted onto a poly(tetrafluoroethylene) (PTFE) plate by the oxygen plasma treatment and subsequent photografting. The surfaces of the grafted PTFE plates prepared at shorter plasma treatment times and/or at lower monomer concentrations were modified hydrophilic at lower grafted amounts. Water absorptivity of the grafted layer increased with the grafted amount and the grafted layers formed at lower monomer concentrations possessed higher water absorptivity. For grafted PTFE plates prepared at the monomer concentration of 1.5 and 2.0 M after the plasma treatment, the substrate breaking occurred. The grafted amount at substrate breaking decreased with a decrease in the plasma treatment time, indicating that the location of photografting was restricted to the outer surface region at shorter plasma treatment times. It was made clear that the combination of the oxygen plasma treatment with the photografting of MAA was an effective procedure to modify the PTFE surface.
ABSTRACTHalloysite nanotube (HNT), a natural clay, was modified with branched polyethyleneimine (... more ABSTRACTHalloysite nanotube (HNT), a natural clay, was modified with branched polyethyleneimine (PEI) to form PEI‐HNT using epichlorohydrin (ECH) as coupling agent, then protonated with HCl to obtain H‐PEI‐HNTs providing [NH3]+[Cl]− functionality for potential antimicrobial properties. Upon PEI modification, zeta potential value of HNTs was increased to +37.3 mV from −34.5 mV and to +41.1 mV for H‐PEI‐HNTs. Only 1.87 wt % H‐element in HNT was increased to 3.03 wt % upon PEI modification along with newly generated elements of N and C at 2.99 and 9.93 wt %, respectively. Moreover, ionic liquid (IL) forms of HNTs with [NH3]+[N(CN)2]−, [NH3]+[PF6]− and [NH3]+[BF4]− functionality were generated via anion exchange of H‐PEI‐HNTs with sodium dicyanamide (SDC), ammonium hexafluorophosphate (AHFP), and sodium tetrafluoroborate (STFB). The antimicrobial properties of the modified, protonated, and IL forms of HNTs were determined via macro dilution, diffusion and agar screening tests against Es...
In this study, the combined use of chitosan and mushroom tyrosinase was applied to remove 1‐napht... more In this study, the combined use of chitosan and mushroom tyrosinase was applied to remove 1‐naphthol and 2‐naphthol from aqueous solutions. In particular, the process parameters, such as the pH value, temperature, and enzyme dose, were discussed for tyrosinase‐catalyzed quinone oxidation of 1‐naphthol. The optimum conditions of enzymatic quinone oxidation of 1‐naphthol were determined to be pH 8.0 and 40°C. Under the optimum conditions, quinone oxidation of 1‐naphthol increased with an increase in the enzyme dose. Quinone derivatives enzymatically generated were chemisorbed on chitosan bead sand. The initial velocity of enzymatic quinone oxidation increased with an increase in the amount of added chitosan beads, since unfavorable interactions between quinone derivatives and tyrosinase in the solutions were restrained by quinone adsorption. 1‐Naphthol was completely removed for 8 h by quinone adsorption on chitosan beads (0.10 cm3/cm3) at 20 U/cm3. The removal time was shortened by i...
In this study, the combined use of a biopolymer chitosan and an oxidoreductase polyphenol oxidase... more In this study, the combined use of a biopolymer chitosan and an oxidoreductase polyphenol oxidase (PPO) was systematically investigated for removal of bisphenol derivatives from aqueous medium. The process parameters, such as the pH value, temperature, and PPO concentration, were estimated to conduct the enzymatic quinone oxidation of bisphenol derivatives by as little enzyme as possible. Bisphenol derivatives effectively underwent PPO-catalyzed quinone oxidation without H2O2 unlike other oxidoreductases, such as peroxidase and tyrosinase, and the optimum conditions were determined to be pH 7.0 and 40 °C for bisphenol B, bisphenol E, bisphenol O, and bisphenol Z, pH 7.0 and 30 °C for bisphenol C and bisphenol F, and pH 8.0 and 40 °C for bisphenol T. They were completely removed through adsorption of enzymatically generated quinone derivatives on chitosan beads or chitosan powders. Quinone adsorption on chitosan beads or chitosan powders in the heterogeneous system was found to be a ...
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Papers by Yuji Kimura