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Nadège Brun - One of the best experts on this subject based on the ideXlab platform.

  • in situ monitoring of styrene Polymerization using raman spectroscopy multi scale approach of homogeneous and Heterogeneous Polymerization processes
    Journal of Raman Spectroscopy, 2013
    Co-Authors: Nadège Brun, Itab Youssef, Marie-claire Chevrel, David Chapron, Cornélius Schrauwen, Sandrine Hoppe, Patrice Bourson
    Abstract:

    Free radical Polymerization of styrene was monitored in situ by combining Raman spectroscopy to other experimental techniques (gravimetry and rheology). Three different processes were investigated: bulk, emulsion and miniemulsion Polymerization. A complete analysis of the evolution of Raman spectrum during the course of reaction showed that a lot of information about molecular dynamics could be extracted and related to chemical phenomena. In addition, we report for the first time the coupling of Raman spectroscopy to a rheometer in order to monitor styrene bulk Polymerization both at the scale of chemical bonds and at the scale of macroscopic phenomena (viscosity variation). Copyright © 2013 John Wiley & Sons, Ltd.

  • In situ monitoring of styrene Polymerization using Raman spectroscopy. Multi-scale approach of homogeneous and Heterogeneous Polymerization processes
    Journal of Raman Spectroscopy, 2013
    Co-Authors: Nadège Brun, Itab Youssef, Marie-claire Chevrel, David Chapron, Cornélius Schrauwen, Sandrine Hoppe, Patrice Bourson, Alain Durand
    Abstract:

    Free radical Polymerization of styrene was monitored in situ by combining Raman spectroscopy to other experimental techniques (gravimetry and rheology). Three different processes were investigated: bulk, emulsion and miniemulsion Polymerization. A complete analysis of the evolution of Raman spectrum during the course of reaction showed that a lot of information about molecular dynamics could be extracted and related to chemical phenomena. In addition, we report for the first time the coupling of Raman spectroscopy to a rheometer in order to monitor styrene bulk Polymerization both at the scale of chemical bonds and at the scale of macroscopic phenomena (viscosity variation).

Gabor A Somorjai - One of the best experts on this subject based on the ideXlab platform.

  • Surface science approach to the preparation and characterization of model Ziegler–Natta Heterogeneous Polymerization catalysts
    Topics in Catalysis, 1999
    Co-Authors: Tamás I. Korányi, Enrico Magni, Gabor A Somorjai
    Abstract:

    Ziegler–Natta Heterogeneous catalytic systems are extensively used to polymerize ethylene and propylene. Some industrial catalysts consist of TiCl_4 chemisorbed on activated MgCl_2 and subsequently reduced and alkylated by reaction with an aluminum alkyl (generally AlEt_3). Lewis bases are added to the catalytic systems to control the enantio-selectivity for the production of isotactic polypropylene. Our aim is to clarify the chemical composition of the active centers by modern surface science methods. Model catalysts are prepared in the form of ultra-thin films by gas-phase deposition on a gold foil in ultrahigh vacuum. Under these conditions, MgCl_2 films grow to controlled thickness via a layer-by-layer mechanism, as revealed by AES and XPS. TiCl_4 can be deposited on these films near room temperature by both electron irradiation-induced and metallic magnesium-induced chemical vapor deposition. Angle-resolved XPS studies indicate that these films consist of a few layers of TiCl_2 with one monolayer of TiCl_4 chemisorbed on its surface. The exposure of these titanium chloride films to the co-catalyst AlEt_3 produces an active model Ziegler–Natta catalyst. XPS analysis reveals the presence of TiCl_2Et on the catalyst surface: this is believed to be the active site. Prolonged reaction with the co-catalyst reduces the titanium sites to TiClEt_n (n = 1 and/or 2). High molecular weight polyethylene and polypropylene are synthesized on these catalysts, as shown by Raman spectroscopy. Highly isotactic polypropylene is produced without need for stereo-regulating Lewis bases.

  • surface science approach to the preparation and characterization of model ziegler natta Heterogeneous Polymerization catalysts
    Topics in Catalysis, 1999
    Co-Authors: Tamás I. Korányi, Gabor A Somorjai, Enrico Magni
    Abstract:

    Ziegler–Natta Heterogeneous catalytic systems are extensively used to polymerize ethylene and propylene. Some industrial catalysts consist of TiCl4 chemisorbed on activated MgCl2 and subsequently reduced and alkylated by reaction with an aluminum alkyl (generally AlEt3). Lewis bases are added to the catalytic systems to control the enantio-selectivity for the production of isotactic polypropylene. Our aim is to clarify the chemical composition of the active centers by modern surface science methods. Model catalysts are prepared in the form of ultra-thin films by gas-phase deposition on a gold foil in ultrahigh vacuum. Under these conditions, MgCl2 films grow to controlled thickness via a layer-by-layer mechanism, as revealed by AES and XPS. TiCl4 can be deposited on these films near room temperature by both electron irradiation-induced and metallic magnesium-induced chemical vapor deposition. Angle-resolved XPS studies indicate that these films consist of a few layers of TiCl2 with one monolayer of TiCl4 chemisorbed on its surface. The exposure of these titanium chloride films to the co-catalyst AlEt3 produces an active model Ziegler–Natta catalyst. XPS analysis reveals the presence of TiCl2Et on the catalyst surface: this is believed to be the active site. Prolonged reaction with the co-catalyst reduces the titanium sites to TiClEtn (n = 1 and/or 2). High molecular weight polyethylene and polypropylene are synthesized on these catalysts, as shown by Raman spectroscopy. Highly isotactic polypropylene is produced without need for stereo-regulating Lewis bases.

Patrice Bourson - One of the best experts on this subject based on the ideXlab platform.

  • in situ monitoring of styrene Polymerization using raman spectroscopy multi scale approach of homogeneous and Heterogeneous Polymerization processes
    Journal of Raman Spectroscopy, 2013
    Co-Authors: Nadège Brun, Itab Youssef, Marie-claire Chevrel, David Chapron, Cornélius Schrauwen, Sandrine Hoppe, Patrice Bourson
    Abstract:

    Free radical Polymerization of styrene was monitored in situ by combining Raman spectroscopy to other experimental techniques (gravimetry and rheology). Three different processes were investigated: bulk, emulsion and miniemulsion Polymerization. A complete analysis of the evolution of Raman spectrum during the course of reaction showed that a lot of information about molecular dynamics could be extracted and related to chemical phenomena. In addition, we report for the first time the coupling of Raman spectroscopy to a rheometer in order to monitor styrene bulk Polymerization both at the scale of chemical bonds and at the scale of macroscopic phenomena (viscosity variation). Copyright © 2013 John Wiley & Sons, Ltd.

  • In situ monitoring of styrene Polymerization using Raman spectroscopy. Multi-scale approach of homogeneous and Heterogeneous Polymerization processes
    Journal of Raman Spectroscopy, 2013
    Co-Authors: Nadège Brun, Itab Youssef, Marie-claire Chevrel, David Chapron, Cornélius Schrauwen, Sandrine Hoppe, Patrice Bourson, Alain Durand
    Abstract:

    Free radical Polymerization of styrene was monitored in situ by combining Raman spectroscopy to other experimental techniques (gravimetry and rheology). Three different processes were investigated: bulk, emulsion and miniemulsion Polymerization. A complete analysis of the evolution of Raman spectrum during the course of reaction showed that a lot of information about molecular dynamics could be extracted and related to chemical phenomena. In addition, we report for the first time the coupling of Raman spectroscopy to a rheometer in order to monitor styrene bulk Polymerization both at the scale of chemical bonds and at the scale of macroscopic phenomena (viscosity variation).

David Chapron - One of the best experts on this subject based on the ideXlab platform.

  • in situ monitoring of styrene Polymerization using raman spectroscopy multi scale approach of homogeneous and Heterogeneous Polymerization processes
    Journal of Raman Spectroscopy, 2013
    Co-Authors: Nadège Brun, Itab Youssef, Marie-claire Chevrel, David Chapron, Cornélius Schrauwen, Sandrine Hoppe, Patrice Bourson
    Abstract:

    Free radical Polymerization of styrene was monitored in situ by combining Raman spectroscopy to other experimental techniques (gravimetry and rheology). Three different processes were investigated: bulk, emulsion and miniemulsion Polymerization. A complete analysis of the evolution of Raman spectrum during the course of reaction showed that a lot of information about molecular dynamics could be extracted and related to chemical phenomena. In addition, we report for the first time the coupling of Raman spectroscopy to a rheometer in order to monitor styrene bulk Polymerization both at the scale of chemical bonds and at the scale of macroscopic phenomena (viscosity variation). Copyright © 2013 John Wiley & Sons, Ltd.

  • In situ monitoring of styrene Polymerization using Raman spectroscopy. Multi-scale approach of homogeneous and Heterogeneous Polymerization processes
    Journal of Raman Spectroscopy, 2013
    Co-Authors: Nadège Brun, Itab Youssef, Marie-claire Chevrel, David Chapron, Cornélius Schrauwen, Sandrine Hoppe, Patrice Bourson, Alain Durand
    Abstract:

    Free radical Polymerization of styrene was monitored in situ by combining Raman spectroscopy to other experimental techniques (gravimetry and rheology). Three different processes were investigated: bulk, emulsion and miniemulsion Polymerization. A complete analysis of the evolution of Raman spectrum during the course of reaction showed that a lot of information about molecular dynamics could be extracted and related to chemical phenomena. In addition, we report for the first time the coupling of Raman spectroscopy to a rheometer in order to monitor styrene bulk Polymerization both at the scale of chemical bonds and at the scale of macroscopic phenomena (viscosity variation).

Alain Durand - One of the best experts on this subject based on the ideXlab platform.

  • In situ monitoring of styrene Polymerization using Raman spectroscopy. Multi-scale approach of homogeneous and Heterogeneous Polymerization processes
    Journal of Raman Spectroscopy, 2013
    Co-Authors: Nadège Brun, Itab Youssef, Marie-claire Chevrel, David Chapron, Cornélius Schrauwen, Sandrine Hoppe, Patrice Bourson, Alain Durand
    Abstract:

    Free radical Polymerization of styrene was monitored in situ by combining Raman spectroscopy to other experimental techniques (gravimetry and rheology). Three different processes were investigated: bulk, emulsion and miniemulsion Polymerization. A complete analysis of the evolution of Raman spectrum during the course of reaction showed that a lot of information about molecular dynamics could be extracted and related to chemical phenomena. In addition, we report for the first time the coupling of Raman spectroscopy to a rheometer in order to monitor styrene bulk Polymerization both at the scale of chemical bonds and at the scale of macroscopic phenomena (viscosity variation).