SÍNTESIS DE PE-comb-(PI-block-PS) MEDIANTE POLIMERIZACIÓN POR COORDINACIÓN DE MACROMONÓMEROS CATALIZADA POR CGC-Ti/MAO

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Coordination homopolymerization of omega-undecenyl poly(styrene-block-isoprene) macromonomers in the presence of CGC-Ti/MAO complexes

This paper deals with the coordination homopolymerization of omega-undecenyl poly(styrene-block-isoprene) macromonomers. The synthesis of the macromonomers made use of an anionic living poly(styrene-block-isoprene) copolymer which is deactivated at low temperature by 11-bromo-1-undecene. The ability of these macromonomers to get involved in coordination homopolymerization in the presence of selected titanium catalysts was discussed. Special emphasis was given to the influence of polymerization temperature, macromonomer molar mass and concentration on the yield of homopolymerization and average degree of polymerization (DPn). in the presence of the CGC-Ti/MAO catalyst, macromonomer conversion, determined by SEC, was between 35 to 52 wt.-%, and DPn was between 5 to 14 depending upon the experimental conditions. However, as revealed by SEC/LS, the resulting comb-shaped polymers (PE-graft-(PI-block-PS), are characterized by sharp molar distributions. Increasing macromonomer molar mass, led to only a slight decrease Of DPn whereas conversion increased moderately. Other titanium catalysts such as CpTiCl3/MAO and Cp*TiCl3/MAO only caused macromonomer dimerization

Macromonomers and coordination polymerization

International audienceThe present work discusses the synthesis of well‐defined comb‐shaped polymers or graft copolymer structures based on coordination (co)polymerization of macromonomers. Polystyrene macromonomers with various polymerizable entities were synthesized first by induced deactivation reactions. The homopolymerization of these macromonomers in the presence of selected early or late transition metal catalysts was examined. Comb‐shaped polymers could be obtained over a large range of DP values. The results were compared to those obtained by anionic homopolymerization. Some results on the copolymerization of these PS macromonomers with ethylene in the presence of VERSIPOLTM type catalysts were presented

New materials designed by coordination polymerization of omega-undecenyl macromonomers

The major part of the present paper discusses the ability of well-defined omega-undecenyl polystyrene, polyisoprene or poly(styrene-block-isoprene) macromonomers to undergo coordination homopolymerization in the presence of selected titanium catalysts. Special emphasis is given to the influence of the nature of the catalyst, the polymerization temperature and the macromonomer molar mass and concentration on homopolymerization yield and average degree of homopolymerization (DPn). Titanium-based catalytic systems such as CpTiCl3/MAO and Cp*TiCl3/MAO only yielded dimers. The use of the homogeneous metallocene catalyst with constrained ligand geometry (CGC-Ti/MAO) having an open active site, significantly improved the degree of polymerization. increasing macromonomer molar mass, causes only a slight decrease of DPn whereas conversion increased moderately. The final section briefly discusses the copolymerization of omega-undecenyl polystyrene macromonomers with ethylene in the presence of Versipol (TM) catalysts

Design of new styrene enriched polyethylenes via coordination copolymerization of ethylene with mono- or alpha,omega-difunctional polystyrene macromonomers

omega-Allyl, omega-undecenyl and alpha,omega-undecenyl polystyrene macromonomers, well defined in molar mass and functionality, were synthesized via anionic polymerization. Their coordination copolymerization with ethylene with a cationic alpha-diiimine palladium catalyst [(ArN=C(Me)-C(Me)=NAr)Pd(CH2)(3)(COOMe)]+BAr4/-,-, (Ar=2,6-Pr-i(2)-C6H3 and Ar-i=3,5-(CF3)(2)-C6H3) affords access to a new type of graft copolymers constituted of a polyethylene backbone and polystyrene grafts. It was shown that the environment of the terminal double bond of the PS macromonomers has a huge influence on the polymerization behavior. Indeed, an undecenyl end-group is more reactive than an all I end-group. The copolymerization of ethylene with a,W-Undecenyl polystyrene macrornonomers lead to cross-linking for long polymerization time (18 h at 25 degrees C). The influence of several parameters (polymerization temperature. ethylene pressure, concentration) on molar masses and macromonomer incorporation yield was also investigated. Macromonomers having the lowest molar masses were the most reactive. The molar mass of the copolymer increased with ethylene pressure. As expected with Such a chain walking catalyst, the copolymers presented moderately branched to highly branched structures depending on the ethylene pressure. like for the homopolymerization of ethylene. Finally, rheological investigations of the copolymers showed that a few percentage of polystyrene incorporation can change drastically the mechanical properties of the material

Homo- and Copolymerization of -Functional Polystyrene Macromonomers via Coordination Polymerization

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Les dispositifs hors norme de mesure du débit

Non-normalized gauging stations. This paper proposes three methodologies for the determination of discharge using water depth and velocity measurements when international standards are not applicable. Each methodology is illustrated through the use of a practical application. The first methodology deals with the instrumentation of the overflow discharge of a combined sewer overflow chamber. Even if these works are hydraulically very similar to standard weirs, their geometry is generally very complex and sometimes unique. The proposed methodology consists in a hydraulic analysis, the use of 3D computational fluid dynamics and the analysis of the simulated results in order to build simple head – discharge relationships that can be easily used by sewer managers. The second methodology deals with ultrasonic (transit-time) gauging stations where singularities have a significant influence on the link between the measured velocities and the mean velocity. The methodology for such stations is very similar to the previous one, with the exception that the models have to be chosen for simulating the velocity distribution and not only the water level distribution. Finally, the third method deals with the determination of the discharge in a sewer using two water level measurements located in two distant manholes. The methodology here consists in a hydraulic analysis, the use of the backwater curve equation (1D model) and an analysis of the simulated results to build an exploitable relationship.Cet article présente, à travers trois exemples concrets de stations de mesure, trois méthodologies de détermination du débit en fonction de mesures de hauteur d’eau et éventuellement de vitesse dans le cas où aucune norme internationale n’est applicable. La première méthode s’intéresse à l’instrumentation du débit déversé d’un déversoir d’eau excédentaire. Hydrauliquement similaires à des seuils, les déversoirs ont néanmoins une géométrie souvent complexe et parfois même unique. La méthodologie proposée repose sur une analyse hydraulique, l’utilisation de la mécanique des fluides numérique 3D et un traitement des résultats dans le but de créer une loi hauteur – débit facilement exploitable. La deuxième méthode concerne le cas d’une station de jaugeage du débit par cordes de vitesse dans un collecteur. La difficulté de ce type de station vient du fait qu’elles sont généralement sous l’influence hydraulique de nombreuses singularités rendant complexe le lien entre les vitesses mesurées et la vitesse moyenne. La méthodologie proposée dans ce cas est très proche de la précédente, à la différence près que le choix des modèles doit être adapté aux variables investiguées (distribution de la vitesse et plus seulement distribution de la hauteur d’eau). Enfin, la troisième méthode s’intéresse à la détermination du débit transitant dans un collecteur au moyen de deux mesures de hauteur d’eau placées dans des regards distants. La méthodologie repose sur une analyse hydraulique, l’utilisation de l’équation de la courbe de remous (modèle 1D) et le traitement des résultats dans l’objectif de les rendre facilement exploitables.Dufresne Matthieu François Daniel, Vazquez José, Bardiaux Jean-Bernard, Isel Sandra, Solliec Laurent. Les dispositifs hors norme de mesure du débit. In: 35es journées de l’hydraulique de la Société Hydrotechnique de France. Hydrométrie 2013. Paris, 15-16 mai 2013. 2013

Inhibition of Human Immunodeficiency Virus Type 1 Reverse Transcriptase, RNase H, and Integrase Activities by Hydroxytropolones

Human immunodeficiency virus type I reverse transcriptase (RT) possesses distinct DNA polymerase and RNase H sites, whereas integrase (IN) uses the same active site to perform 3′-end processing and strand transfer of the proviral DNA. These four enzymatic activities are essential for viral replication and require metal ions. Two Mg(2+) ions are present in the RT polymerase site, and one or two Mg(2+) ions are required for the catalytic activities of RNase H and IN. We tested the possibility of inhibition of the RT polymerase and RNase H as well as the IN 3′-end processing and transfer activities of purified enzymes by a series of 3,7-dihydroxytropolones designed to target two Mg(2+) ions separated by ∼3.7 Å. The RT polymerase and IN 3′ processing and strand transfer activities were inhibited at submicromolar concentrations, while the RNase H activity was inhibited in the low micromolar range. In all cases, the lack of inhibition by tropolones and O-methylated 3,7-dihydroxytropolones was consistent with the active molecules binding the metal ions in the active site. In addition, inhibition of the DNA polymerase activity was shown to depend on the Mg(2+) concentration. Furthermore, selective inhibitors were identified for several of the activities tested, leaving some potential for design of improved inhibitors. However, all tested compounds exhibited cellular toxicity that presently limits their applications