The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Ryo Yoshida - One of the best experts on this subject based on the ideXlab platform.
-
self Oscillating gel composed of thermosensitive polymer exhibiting higher lcst
Journal of Controlled Release, 2011Co-Authors: Mio Hidaka, Ryo YoshidaAbstract:Abstract We have developed self-Oscillating polymers and gels as novel biomimetic materials by utilizing an Oscillating reaction, known as the Belousov–Zhabotinsky (BZ) reaction. The self-Oscillating polymer gel is composed of a poly(N-isopropylacrylamide) (PNIPAAm) network in which the catalyst for the BZ reaction is covalently immobilized. Under the coexistence of the reactants, the gel undergoes spontaneous cyclic swelling–deswelling changes without any on–off switching of external stimuli. In order to induce self-oscillation while maintaining a larger amplitude at higher temperatures and around body temperature for potential applications to biomaterials, etc., here we prepared a self-Oscillating gel composed of a thermosensitive N,N′-ethylmethylacrylamide (EMAAm) polymer exhibiting a higher LCST than that of the NIPAAm polymer. The self-Oscillating Behavior of the poly(EMAAm-co-Ru(bpy)3) gel was investigated by comparing against gels composed of a thermosensitive NIPAAm polymer with a lower LCST or non-thermosensitive N,N′-dimethylacrylamide (DMAAm) polymer. The design concept of self-oscillation at higher temperatures without a decrease in swelling–deswelling amplitude was demonstrated by utilizing a thermosensitive polymer exhibiting a higher LCST.
-
a viscosity self oscillation of polymer solution induced by the belousov zhabotinsky reaction under acid free condition
Journal of Chemical Physics, 2008Co-Authors: Yusuke Hara, Ryo YoshidaAbstract:We succeeded in measuring a viscosity self-oscillation induced by the Belousov-Zhabotinsky (BZ) reaction for a polymer solution on the constant temperature condition under acid-free condition. The polymer chain is consisted of N-isopropylacrylamide, ruthenium complex as a catalyst of the BZ reaction, and an acrylamide-2-methylpropanesulfonic acid (AMPS) as a pH and the solubility control site. The viscosity self-oscillation for the AMPS-containing polymer solution was attributed to the difference between viscosities for the polymer solution in the reduced and oxidized states. The effects of the polymer concentration and the temperature of the polymer solution on the viscosity self-oscillation were investigated. As a result, the viscosity self-Oscillating Behavior significantly depended on the polymer concentration and the temperature of the polymer solution. The period of the viscosity self-oscillation decreased with increasing temperature in accordance with the Arrenius equation.
-
Self-Oscillating soluble-insoluble changes of a polymer chain including an oxidizing agent induced by the Belousov-Zhabotinsky reaction.
The journal of physical chemistry. B, 2005Co-Authors: Yusuke Hara, Shingo Maeda, Shuji Hashimoto, Takamasa Sakai, Ryo YoshidaAbstract:A new type of self-Oscillating polymer was prepared by utilizing the Belousov-Zhabotinsky reaction. In this study, capture sites with a positive charge for an oxidizing agent as a counterion were incorporated into the copolymer of N-isopropylacrylamide and the ruthenium complex as a catalyst. Soluble-insoluble self-oscillation of the polymer was first achieved without adding an oxidizing agent. The effect of temperature on the self-Oscillating Behavior was investigated. It was clarified that the polymer had two advantageous characteristics because of the higher LCST; one is to enable self-oscillation around body temperature, and the other is to cause the oscillation for a longer time without intermolecular aggregation among the polymer chains in the reduced state. This achievement of self-oscillation of polymer chains including an oxidizing agent may lead to their practical use under oxidant-free conditions.
-
control of Oscillating Behavior for the self Oscillating polymer with ph control site
Langmuir, 2005Co-Authors: Yusuke Hara, Ryo YoshidaAbstract:A novel self-Oscillating polymer was prepared by copolymerizing the catalyst for the Belousov-Zhabotinsky reaction with N-isopropylacrylamide. Further, by introducing acrylamide-2-methylpropane sulfonic acid (AMPS) with a sulfonic acid group as a pH-control site into the polymer, self-oscillation under acid-free conditions was achieved. The period and amplitude for the self-oscillation is controllable by changing the composition of the polymer. On-off switching of self-oscillation is also possible by changing temperature or substrate concentrations. The AMPS plays an important role not only to control the pH but also to change the solubility of the polymer.
-
self oscillation of polymer chains induced by the belousov zhabotinsky reaction under acid free conditions
Journal of Physical Chemistry B, 2005Co-Authors: Yusuke Hara, Ryo YoshidaAbstract:A novel self-Oscillating polymer was prepared by utilizing the Belousov-Zhabotinsky (BZ) reaction. In this study, a sulfonic acid group was newly introduced as a pH-control site into the copolymer of N-isopropylacrylamide, and the ruthenium complex was introduced as a catalyst site. By introducing the pH-control site, we succeed in causing the soluble-insoluble self-oscillation of the polymer solution under acid-free conditions in which only two BZ substrates, malonic acid and sodium bromate, were present as added agents. The self-Oscillating Behavior was remarkably influenced by the temperature and polymer concentration, which reflects the intermolecular aggregative capacity of the polymer chains in the reduced state to change the lower critical solution temperature. This achievement of self-oscillation of polymer chains under acid-free conditions may lead to their practical use as novel biomimetic materials under biological conditions.
Yusuke Hara - One of the best experts on this subject based on the ideXlab platform.
-
Effect of polymer concentration on the lifetime and transmittance Behavior of a self-Oscillating polymer chain with a high lower critical solution temperature
MATEC Web of Conferences, 2017Co-Authors: Tomoka Nakazumi, Yusuke HaraAbstract:In this study, we investigated the lifetime and self-Oscillating Behavior of a polymer chain with a high lower critical solution temperature (LCST). The polymer chain comprised 4-vinyl-4´-methyl-2,2´-bipyridinebis(2,2´-bipyridine)bis(hexafluorophosphate) ruthenium as catalyst for the Belousov–Zhabotinsky reaction and N-ethylacrylamide as the polymer main-chain with a high LCST when compared to N-isopropylacrylamide. We demonstrated that the self-Oscillating Behavior was significantly affected by the polymer concentration and measuring temperature. Moreover, we established that the lifetime of the transmittance self-oscillation can be predicted from the polymer concentration and measuring temperature.
-
influence of the belousov zhabotinsky substrate concentration on the lifetime and self Oscillating Behavior of a polymer solution
MATEC Web of Conferences, 2017Co-Authors: Tomoka Nakazumi, Yusuke HaraAbstract:In this study, we synthesized a self-Oscillating polymer chain with N-ethylacrylamide (NEAAm) as the main-chain. This exhibits a higher lower critical solution temperature than an N-isopropylacrylamide main chain. We subsequently measured the transmittance self-oscillation of poly[NEAAm-co-Ru(bpy) 3 ] [Ru(bpy) 3 = 4-vinyl-4’-methyl-2,2’-bipyridinebis(2,2’ bipyridine)bis(hexafluorophosphate) ruthenium] solutions comprising three Belousov-Zhabotinsky (BZ) substrates (malonic acid, sodium bromate, and sulfuric acid), under stirring at constant temperature. The soluble-insoluble self-oscillation of the polymer solution originated from the different solubility of the Ru(bpy) 3 moiety as a catalyst of the BZ reaction in the reduced and oxidized states. We demonstrated that the self-Oscillating Behavior was significantly affected by the initial concentration of the sodium bromate. Moreover, we clarified that the lifetime of the transmittance self-oscillation can be predicted from the initial concentration of malonic acid.
-
autonomous self Oscillating Behavior of a novel nonthermoresponsive polymer chain
Advanced Materials Research, 2012Co-Authors: Yusuke Hara, Rumana A JahanAbstract:In this paper, we investigated the influence of the temperatureand the initial concentrations of malonic acid on the transmittance self-oscillation for a novel nonthermoresponsivepolymer chain. The amplitude of the self-oscillation hardly changes while change in the temperature and the concentration of malonic acid. The period of the self-oscillation does not decrease with increase in the concentration of malonic acid at 14, 16 and 18 °C.
-
trasmittance self Oscillating Behavior of a non thermoresponsive polymer chain induced by the belouzov zhabotinsky bz reaction
Key Engineering Materials, 2011Co-Authors: Yusuke HaraAbstract:In this study, the influence of the temperature on the transmittance self-oscillation of a non-thermoresponsive polymer chain was investigated. The polymer chain was composed of a biocompatible and non-thermoresponsive poly-vinylpyrrolidone (PVP) main-chain covalently-bonded to the 10 wt% ruthenium catalyst moiety (Ru(bpy)3) of the BZ reaction. As a result, the amplitude of the transmittance self-oscillation slightly decreased with the increase in the temperature. The period of the transmittance self-oscillation decreased with increasing the temperature in accordance with the Arrenius equation. Therefore, the period of the self-oscillation can be controlled by the selection of the temperature.
-
control of autonomous swelling deswelling Behavior for a polymer gel
Journal of Physical Chemistry B, 2009Co-Authors: Satoshi Nakamaru, Yusuke Hara, Shingo Maeda, Shuji HashimotoAbstract:We succeeded in the wide-range control of the period for the swelling−deswelling self-oscillation of a novel polymer gel by selection of the initial concentration of the Belouzov−Zhabotinsky (BZ) substrates and the temperature. The novel polymer gel was composed of a non-thermoresponsive and biocompatible poly(vinylpyrrolidone) (PVP) main chain covalently bonded to the ruthenium catalyst for the BZ reaction. In this study, we clarified the influence of the initial concentration of the BZ substrates and the temperature on the period and the self-Oscillating Behavior. By optimizing the initial concentration of the BZ substrates, we caused the swelling−deswelling self-oscillation in 0.5 Hz. The maximum frequency (0.5 Hz) of the novel gel was 20 times as large as that for the conventional-type self-Oscillating gel. Moreover, we showed that the displacement of the self-oscillation for the gel has a tradeoff relationship against the period of the self-oscillation.
Siglinda Perathoner - One of the best experts on this subject based on the ideXlab platform.
-
Oscillating Behavior in n2o decomposition over rh supported on zirconia based catalysts 2 analysis of the reaction mechanism
Journal of Catalysis, 2000Co-Authors: Gabriele Centi, Laura Dallolio, Siglinda PerathonerAbstract:The mechanism responsible for the Oscillating Behavior in N2O decomposition of rhodium particles supported on zirconia-based oxides in the presence of oxygen and water is studied using transient reactivity and thermogravimetric tests. The Behavior over different oxide supports is also reported. The results demonstrate that (i) the atomic oxygen produced in the decomposition of N2O remains chemisorbed on the Rh surface, leading to its progressive accumulation, (ii) the activity of the catalyst increases progressively with increasing coverage of Rh with oxygen, and (iii) above a threshold concentration of oxygen on the Rh surface, a rapid reconstruction of Rh particles occurs with release of the chemisorbed oxygen and the start of a new oscillation cycle, but only in the presence of water in the feed. It is also shown that the presence of water in the feed, inducing the desorption of chemisorbed oxygen from the Rh surface, stabilizes a more reduced working state of the catalyst surface.
-
Oscillating Behavior in n2o decomposition over rh supported on zirconia based catalysts the role of the reaction conditions
Journal of Catalysis, 2000Co-Authors: Gabriele Centi, Laura Dallolio, Siglinda PerathonerAbstract:Abstract Rhodium particles supported on zirconia doped with neodymium oxide show an Oscillating Behavior in N 2 O decomposition in the presence of oxygen and water, but the Oscillating Behavior occurs only when the zirconia surface is hydrated. The phenomenon is ascribed to a dynamic process of surface accumulation of atomic oxygen (produced by N 2 O dissociation) on the Rh surface and reconstruction of these supported Rh particles above a level of oxygen coverage, with a rapid drop in the activity and release of gaseous dioxygen. This in situ reconstruction of Rh particles, however, may occur only on a hydrated surface.
Gabriele Centi - One of the best experts on this subject based on the ideXlab platform.
-
Oscillating Behavior in n2o decomposition over rh supported on zirconia based catalysts 2 analysis of the reaction mechanism
Journal of Catalysis, 2000Co-Authors: Gabriele Centi, Laura Dallolio, Siglinda PerathonerAbstract:The mechanism responsible for the Oscillating Behavior in N2O decomposition of rhodium particles supported on zirconia-based oxides in the presence of oxygen and water is studied using transient reactivity and thermogravimetric tests. The Behavior over different oxide supports is also reported. The results demonstrate that (i) the atomic oxygen produced in the decomposition of N2O remains chemisorbed on the Rh surface, leading to its progressive accumulation, (ii) the activity of the catalyst increases progressively with increasing coverage of Rh with oxygen, and (iii) above a threshold concentration of oxygen on the Rh surface, a rapid reconstruction of Rh particles occurs with release of the chemisorbed oxygen and the start of a new oscillation cycle, but only in the presence of water in the feed. It is also shown that the presence of water in the feed, inducing the desorption of chemisorbed oxygen from the Rh surface, stabilizes a more reduced working state of the catalyst surface.
-
Oscillating Behavior in n2o decomposition over rh supported on zirconia based catalysts the role of the reaction conditions
Journal of Catalysis, 2000Co-Authors: Gabriele Centi, Laura Dallolio, Siglinda PerathonerAbstract:Abstract Rhodium particles supported on zirconia doped with neodymium oxide show an Oscillating Behavior in N 2 O decomposition in the presence of oxygen and water, but the Oscillating Behavior occurs only when the zirconia surface is hydrated. The phenomenon is ascribed to a dynamic process of surface accumulation of atomic oxygen (produced by N 2 O dissociation) on the Rh surface and reconstruction of these supported Rh particles above a level of oxygen coverage, with a rapid drop in the activity and release of gaseous dioxygen. This in situ reconstruction of Rh particles, however, may occur only on a hydrated surface.
Laura Dallolio - One of the best experts on this subject based on the ideXlab platform.
-
Oscillating Behavior in n2o decomposition over rh supported on zirconia based catalysts 2 analysis of the reaction mechanism
Journal of Catalysis, 2000Co-Authors: Gabriele Centi, Laura Dallolio, Siglinda PerathonerAbstract:The mechanism responsible for the Oscillating Behavior in N2O decomposition of rhodium particles supported on zirconia-based oxides in the presence of oxygen and water is studied using transient reactivity and thermogravimetric tests. The Behavior over different oxide supports is also reported. The results demonstrate that (i) the atomic oxygen produced in the decomposition of N2O remains chemisorbed on the Rh surface, leading to its progressive accumulation, (ii) the activity of the catalyst increases progressively with increasing coverage of Rh with oxygen, and (iii) above a threshold concentration of oxygen on the Rh surface, a rapid reconstruction of Rh particles occurs with release of the chemisorbed oxygen and the start of a new oscillation cycle, but only in the presence of water in the feed. It is also shown that the presence of water in the feed, inducing the desorption of chemisorbed oxygen from the Rh surface, stabilizes a more reduced working state of the catalyst surface.
-
Oscillating Behavior in n2o decomposition over rh supported on zirconia based catalysts the role of the reaction conditions
Journal of Catalysis, 2000Co-Authors: Gabriele Centi, Laura Dallolio, Siglinda PerathonerAbstract:Abstract Rhodium particles supported on zirconia doped with neodymium oxide show an Oscillating Behavior in N 2 O decomposition in the presence of oxygen and water, but the Oscillating Behavior occurs only when the zirconia surface is hydrated. The phenomenon is ascribed to a dynamic process of surface accumulation of atomic oxygen (produced by N 2 O dissociation) on the Rh surface and reconstruction of these supported Rh particles above a level of oxygen coverage, with a rapid drop in the activity and release of gaseous dioxygen. This in situ reconstruction of Rh particles, however, may occur only on a hydrated surface.