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Nicholas J. Turro - One of the best experts on this subject based on the ideXlab platform.
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Mechanistic Study of photoinitiated free radical polymerization using thioxanthone thioacetic acid as one component type ii photoinitiator
Macromolecules, 2005Co-Authors: Meral Aydin, Steffen Jockusch, Nergis Arsu, Yusuf Yagci, Nicholas J. TurroAbstract:A Mechanistic Study concerning photoinitiated free radical polymerization using thioxanthone thio-acetic acid (TX−S−CH2−COOH) as one-component Type II photoinitiator was performed. Steady-state and time-resolved fluorescence and phosphorescence spectroscopy, as well as laser flash photolysis was employed to Study the photophysics and photochemistry of TX−S−CH2−COOH. The initiator undergoes efficient intersystem crossing into the triplet state and the lowest triplet state posseses π−π* configuration. In contrast to the unsubstituted thioxanthone, TX−S−CH2−COOH shows an unusually short triplet lifetime (65 ns) indicating an intramolecular reaction. From fluoroscence, phosphorescence, and laser flash photolysis studies, in conjunction with photopolymerization experiments, we propose that TX−S−CH2−COOH triplets undergo intramolecular electron transfer followed by hydrogen abstraction and decarboxylation producing alkyl radicals, which are the active initiator radicals in photoinduced polymerization. At low in...
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Mechanistic Study of photoinitiated free radical polymerization using thioxanthone thioacetic acid as one-component type II photoinitiator
Macromolecules, 2005Co-Authors: Meral Aydin, Steffen Jockusch, Nergis Arsu, Yusuf Yagci, Nicholas J. TurroAbstract:A Mechanistic Study concerning photoinitiated free radical polymerization using thioxanthone thio-acetic acid (TX?S?CH2?COOH) as one-component Type II photoinitiator was performed. Steady-state and time-resolved fluorescence and phosphorescence spectroscopy, as well as laser flash photolysis was employed to Study the photophysics and photochemistry of TX?S?CH2?COOH. The initiator undergoes efficient intersystem crossing into the triplet state and the lowest triplet state posseses ???* configuration. In contrast to the unsubstituted thioxanthone, TX?S?CH2?COOH shows an unusually short triplet lifetime (65 ns) indicating an intramolecular reaction. From fluoroscence, phosphorescence, and laser flash photolysis studies, in conjunction with photopolymerization experiments, we propose that TX?S?CH2?COOH triplets undergo intramolecular electron transfer followed by hydrogen abstraction and decarboxylation producing alkyl radicals, which are the active initiator radicals in photoinduced polymerization. At low initiator concentrations (below 5 × 10-3 M) this intramolecular reaction is the dominant path. At concentrations above 5 × 10-3 M, however, the respective intermolecular reactions may be operative.
Patricio Ruiz - One of the best experts on this subject based on the ideXlab platform.
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Mechanistic Study of low temperature co2 methanation over rh tio2 catalysts
Journal of Catalysis, 2013Co-Authors: Alejandro Karelovic Burotto, Patricio RuizAbstract:CO2 methanation at low temperature and atmospheric pressure was studied over Rh/TiO2 catalysts focusing on the effect of Rh particle size on the activity and reaction mechanism. Catalysts with different Rh contents (0.5–5 wt.%) were prepared in order to obtain different mean cluster sizes. The activity was measured between 85 and 165 °C, with a H2/CO2 ratio equal to 4. The rate of methane production per surface Rh atoms increases as metal particle size increases up to ca. 7 nm. Beyond this size, the rate does not change appreciably. Higher activation energies (up to 28.7 kcal/mol) are obtained for catalysts with small cluster size (ca. 2 nm), whereas for larger particles (>7 nm), the activation energy is lower and does not change with size (ca. 17 kcal/mol). Reaction order with respect to CO2 is near zero for large clusters, whereas it decreases to −0.36 for lower size clusters. From the analysis of adsorbed species using operando-DRIFTS, it is proposed that smaller Rh particles tend to bind CO(ads) intermediate stronger than larger ones. The activation energy for the dissociation of adsorbed CO species does not vary with Rh particle size, which suggests that smaller particles are not intrinsically less active, but they present less active sites than larger ones. The Study of the kinetic parameters permits to propose that CO(ads) dissociation is aided by the presence of H species and that a likely surface intermediate is Rh carbonyl hydrides.
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Mechanistic Study of low temperature CO2 methanation over Rh/TiO2 catalysts
Journal of Catalysis, 2013Co-Authors: Alejandro Karelovic, Patricio RuizAbstract:CO2 methanation at low temperature and atmospheric pressure was studied over Rh/TiO2 catalysts focusing on the effect of Rh particle size on the activity and reaction mechanism. Catalysts with different Rh contents (0.5-5 wt.%) were prepared in order to obtain different mean cluster sizes. The activity was measured between 85 and 165 °C, with a H 2/CO2 ratio equal to 4. The rate of methane production per surface Rh atoms increases as metal particle size increases up to ca. 7 nm. Beyond this size, the rate does not change appreciably. Higher activation energies (up to 28.7 kcal/mol) are obtained for catalysts with small cluster size (ca. 2 nm), whereas for larger particles (>7 nm), the activation energy is lower and does not change with size (ca. 17 kcal/mol). Reaction order with respect to CO2 is near zero for large clusters, whereas it decreases to -0.36 for lower size clusters. From the analysis of adsorbed species using operando-DRIFTS, it is proposed that smaller Rh particles tend to bind CO(ads) intermediate stronger than larger ones. The activation energy for the dissociation of adsorbed CO species does not vary with Rh particle size, which suggests that smaller particles are not intrinsically less active, but they present less active sites than larger ones. The Study of the kinetic parameters permits to propose that CO(ads) dissociation is aided by the presence of H species and that a likely surface intermediate is Rh carbonyl hydrides. © 2013 Elsevier Inc. All rights reserved.
Meral Aydin - One of the best experts on this subject based on the ideXlab platform.
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Mechanistic Study of photoinitiated free radical polymerization using thioxanthone thioacetic acid as one component type ii photoinitiator
Macromolecules, 2005Co-Authors: Meral Aydin, Steffen Jockusch, Nergis Arsu, Yusuf Yagci, Nicholas J. TurroAbstract:A Mechanistic Study concerning photoinitiated free radical polymerization using thioxanthone thio-acetic acid (TX−S−CH2−COOH) as one-component Type II photoinitiator was performed. Steady-state and time-resolved fluorescence and phosphorescence spectroscopy, as well as laser flash photolysis was employed to Study the photophysics and photochemistry of TX−S−CH2−COOH. The initiator undergoes efficient intersystem crossing into the triplet state and the lowest triplet state posseses π−π* configuration. In contrast to the unsubstituted thioxanthone, TX−S−CH2−COOH shows an unusually short triplet lifetime (65 ns) indicating an intramolecular reaction. From fluoroscence, phosphorescence, and laser flash photolysis studies, in conjunction with photopolymerization experiments, we propose that TX−S−CH2−COOH triplets undergo intramolecular electron transfer followed by hydrogen abstraction and decarboxylation producing alkyl radicals, which are the active initiator radicals in photoinduced polymerization. At low in...
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Mechanistic Study of photoinitiated free radical polymerization using thioxanthone thioacetic acid as one-component type II photoinitiator
Macromolecules, 2005Co-Authors: Meral Aydin, Steffen Jockusch, Nergis Arsu, Yusuf Yagci, Nicholas J. TurroAbstract:A Mechanistic Study concerning photoinitiated free radical polymerization using thioxanthone thio-acetic acid (TX?S?CH2?COOH) as one-component Type II photoinitiator was performed. Steady-state and time-resolved fluorescence and phosphorescence spectroscopy, as well as laser flash photolysis was employed to Study the photophysics and photochemistry of TX?S?CH2?COOH. The initiator undergoes efficient intersystem crossing into the triplet state and the lowest triplet state posseses ???* configuration. In contrast to the unsubstituted thioxanthone, TX?S?CH2?COOH shows an unusually short triplet lifetime (65 ns) indicating an intramolecular reaction. From fluoroscence, phosphorescence, and laser flash photolysis studies, in conjunction with photopolymerization experiments, we propose that TX?S?CH2?COOH triplets undergo intramolecular electron transfer followed by hydrogen abstraction and decarboxylation producing alkyl radicals, which are the active initiator radicals in photoinduced polymerization. At low initiator concentrations (below 5 × 10-3 M) this intramolecular reaction is the dominant path. At concentrations above 5 × 10-3 M, however, the respective intermolecular reactions may be operative.
Nergis Arsu - One of the best experts on this subject based on the ideXlab platform.
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Mechanistic Study of photoinitiated free radical polymerization using thioxanthone thioacetic acid as one component type ii photoinitiator
Macromolecules, 2005Co-Authors: Meral Aydin, Steffen Jockusch, Nergis Arsu, Yusuf Yagci, Nicholas J. TurroAbstract:A Mechanistic Study concerning photoinitiated free radical polymerization using thioxanthone thio-acetic acid (TX−S−CH2−COOH) as one-component Type II photoinitiator was performed. Steady-state and time-resolved fluorescence and phosphorescence spectroscopy, as well as laser flash photolysis was employed to Study the photophysics and photochemistry of TX−S−CH2−COOH. The initiator undergoes efficient intersystem crossing into the triplet state and the lowest triplet state posseses π−π* configuration. In contrast to the unsubstituted thioxanthone, TX−S−CH2−COOH shows an unusually short triplet lifetime (65 ns) indicating an intramolecular reaction. From fluoroscence, phosphorescence, and laser flash photolysis studies, in conjunction with photopolymerization experiments, we propose that TX−S−CH2−COOH triplets undergo intramolecular electron transfer followed by hydrogen abstraction and decarboxylation producing alkyl radicals, which are the active initiator radicals in photoinduced polymerization. At low in...
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Mechanistic Study of photoinitiated free radical polymerization using thioxanthone thioacetic acid as one-component type II photoinitiator
Macromolecules, 2005Co-Authors: Meral Aydin, Steffen Jockusch, Nergis Arsu, Yusuf Yagci, Nicholas J. TurroAbstract:A Mechanistic Study concerning photoinitiated free radical polymerization using thioxanthone thio-acetic acid (TX?S?CH2?COOH) as one-component Type II photoinitiator was performed. Steady-state and time-resolved fluorescence and phosphorescence spectroscopy, as well as laser flash photolysis was employed to Study the photophysics and photochemistry of TX?S?CH2?COOH. The initiator undergoes efficient intersystem crossing into the triplet state and the lowest triplet state posseses ???* configuration. In contrast to the unsubstituted thioxanthone, TX?S?CH2?COOH shows an unusually short triplet lifetime (65 ns) indicating an intramolecular reaction. From fluoroscence, phosphorescence, and laser flash photolysis studies, in conjunction with photopolymerization experiments, we propose that TX?S?CH2?COOH triplets undergo intramolecular electron transfer followed by hydrogen abstraction and decarboxylation producing alkyl radicals, which are the active initiator radicals in photoinduced polymerization. At low initiator concentrations (below 5 × 10-3 M) this intramolecular reaction is the dominant path. At concentrations above 5 × 10-3 M, however, the respective intermolecular reactions may be operative.
Yusuf Yagci - One of the best experts on this subject based on the ideXlab platform.
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Mechanistic Study of photoinitiated free radical polymerization using thioxanthone thioacetic acid as one component type ii photoinitiator
Macromolecules, 2005Co-Authors: Meral Aydin, Steffen Jockusch, Nergis Arsu, Yusuf Yagci, Nicholas J. TurroAbstract:A Mechanistic Study concerning photoinitiated free radical polymerization using thioxanthone thio-acetic acid (TX−S−CH2−COOH) as one-component Type II photoinitiator was performed. Steady-state and time-resolved fluorescence and phosphorescence spectroscopy, as well as laser flash photolysis was employed to Study the photophysics and photochemistry of TX−S−CH2−COOH. The initiator undergoes efficient intersystem crossing into the triplet state and the lowest triplet state posseses π−π* configuration. In contrast to the unsubstituted thioxanthone, TX−S−CH2−COOH shows an unusually short triplet lifetime (65 ns) indicating an intramolecular reaction. From fluoroscence, phosphorescence, and laser flash photolysis studies, in conjunction with photopolymerization experiments, we propose that TX−S−CH2−COOH triplets undergo intramolecular electron transfer followed by hydrogen abstraction and decarboxylation producing alkyl radicals, which are the active initiator radicals in photoinduced polymerization. At low in...
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Mechanistic Study of photoinitiated free radical polymerization using thioxanthone thioacetic acid as one-component type II photoinitiator
Macromolecules, 2005Co-Authors: Meral Aydin, Steffen Jockusch, Nergis Arsu, Yusuf Yagci, Nicholas J. TurroAbstract:A Mechanistic Study concerning photoinitiated free radical polymerization using thioxanthone thio-acetic acid (TX?S?CH2?COOH) as one-component Type II photoinitiator was performed. Steady-state and time-resolved fluorescence and phosphorescence spectroscopy, as well as laser flash photolysis was employed to Study the photophysics and photochemistry of TX?S?CH2?COOH. The initiator undergoes efficient intersystem crossing into the triplet state and the lowest triplet state posseses ???* configuration. In contrast to the unsubstituted thioxanthone, TX?S?CH2?COOH shows an unusually short triplet lifetime (65 ns) indicating an intramolecular reaction. From fluoroscence, phosphorescence, and laser flash photolysis studies, in conjunction with photopolymerization experiments, we propose that TX?S?CH2?COOH triplets undergo intramolecular electron transfer followed by hydrogen abstraction and decarboxylation producing alkyl radicals, which are the active initiator radicals in photoinduced polymerization. At low initiator concentrations (below 5 × 10-3 M) this intramolecular reaction is the dominant path. At concentrations above 5 × 10-3 M, however, the respective intermolecular reactions may be operative.