Search results for "ionic"
showing 10 items of 2016 documents
Investigation of the noble gas solubility in H2O–CO2 bearing silicate liquids at moderate pressure II: the extended ionic porosity (EIP) model
2000
A semi-theoretical model is proposed to predict partitioning of noble gases between any silicate liquid and a H2O–CO2 gas phase with noble gas as a minor component, in a large range of pressures (at least up to 300 MPa). The model is based on the relationship between the concentration of dissolved noble gas and ionic porosity of the melt, found by Carroll and Stolper [Geochim. Cosmochim. Acta 57 (1993) 5039–5051] for H2O–CO2 free melts. It evaluates the effect of dissolved H2O and CO2 on the melt ionic porosity and, consequently on Henry’s constants of noble gases. The fugacities of the noble gases in the H2O–CO2–noble gas mixtures are also considered in our equilibrium calculations of diss…
Equilibrium swelling properties of polyampholytic hydrogels
1996
The role of counter ions and ion dissociation in establishing the equilibrium swelling of balanced and unbalanced polyampholytic hydrogels has been investigated experimentally and theoretically. The swelling dependence on both the net charge offset and the external bath salt concentration has been examined using an acrylamide based polyampholytic hydrogels. By careful consideration of the swelling kinetics, we illustrate the effects of ion dissociation equilibria and counter ion shielding in polyampholytic hydrogels near their balance point where both polyelectrolyte and polyampholyte effects are present. The theory considers a Flory type swelling model where the Coulombic interactions betw…
Synthèse et réactivité chimiques et électrochimiques de dérivés d'imidazoliums : vers des procédés éco-responsables
2015
This work deals with the use of electrochemistry as a tool for alternative synthesis of new azolium-based molecules.A new electrosynthesis method was developed for the synthesis of imidazolium carboxylates (masked carbenes) leading to a wide library of compounds. This approach was compared to already reported chemical syntheses. In the current context of sustainable development, bio based products have been synthesized and optimization of the process was achieved in order to reduce waste and energy consumption.The key role of the hydrogenoxalate anion was demonstrated in the synthesis of ionic liquids and/or imidazolium salts. Some of them were employed as recyclable catalysts for Fischer e…
Synchronization protocols in Spanish Merino sheep Reduction in time to estrus by the addition of eCG to a progesterone-based estrus synchronization p…
2015
Abstract An appropriate management of reproduction allows ewes to breed at a more intensive rhythm, more compatible with economic efficiency of farms. Hence, the objectives of the present work were to evaluate a traditional estrus synchronization protocol (based on medroxyprogesterone acetate-impregnated intravaginal sponges combined or not with equine chorionic gonadotropin) on a Merino sheep herd during the breeding season, in order to determine the best working protocol for this breed. A total of 277 sheep, blocked by age (200 ewes and 77 ewe lambs) were randomly allocated to four groups, two of ewes (E and Ee) and two of ewe lambs (L and Le). All females received 60 mg MAP (medroxyproge…
Refractive Indices and Deviations in Refractive Indices for Binary Mixtures of 1-Ethyl-3-methylimidazolium Trifluoromethanesulfonate with Methanol, E…
2009
Refractive indices of the binary mixtures of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([emim][triflate]) with methanol, ethanol, 1-propanol, and 2-propanol were experimentally measured over the whole range of compositions at T = (288.15 to 338.15) K and atmospheric pressure. From the experimental data, deviations in refractive indices have been calculated and fitted to an extended version of the Redlich−Kister equation, which takes into account the dependence on composition and temperature simultaneously. This dependence has been discussed. The deviations are always positive, and their extent follows the sequence methanol > ethanol > 2-propanol > 1-propanol, increasing when tem…
Isobaric Vapor−Liquid Equilibria for Ethyl Acetate + Ethanol + 1-Ethyl-3-methylimidazolium Trifluoromethanesulfonate at 100 kPa
2007
Isobaric vapor−liquid equilibria for the binary systems ethyl acetate + ethanol, ethyl acetate + 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([emim][triflate]), and ethanol + [emim][triflate] as well as the vapor−liquid equilibria for the ethyl acetate + ethanol + [emim][triflate] ternary system have been obtained at 100 kPa using a recirculating still. NRTL fitting parameters for the ethyl acetate + ethanol and ethanol + [emim][triflate] systems were calculated. The measured ternary data were correlated using the Mock electrolyte NRTL model, which reproduces reasonably well the experimental values. The results suggest that the addition of [emim][triflate] to the ethyl acetate + e…
Polymerization of Ethylene Oxide, Propylene Oxide, and Other Alkylene Oxides: Synthesis, Novel Polymer Architectures, and Bioconjugation.
2015
The review summarizes current trends and developments in the polymerization of alkylene oxides in the last two decades since 1995, with a particular focus on the most important epoxide monomers ethylene oxide (EO), propylene oxide (PO), and butylene oxide (BO). Classical synthetic pathways, i.e., anionic polymerization, coordination polymerization, and cationic polymerization of epoxides (oxiranes), are briefly reviewed. The main focus of the review lies on more recent and in some cases metal-free methods for epoxide polymerization, i.e., the activated monomer strategy, the use of organocatalysts, such as N-heterocyclic carbenes (NHCs) and N-heterocyclic olefins (NHOs) as well as phosphazen…
Introducing an amine functionality at the block junction of amphiphilic block copolymers by anionic polymerization strategies
2011
A series of block copolymers bearing a single amino in-chain functionality was synthesized via anionic polymerization of styrene and ethylene oxide. By means of both a conventional and a continuous setup, living polystyrene was quantitatively end functionalized with an oxirane (DBAG) prior to the polymerization of the poly(ethylene oxide) segment. The in-chain amine was conjugated with a fluorescent dye.
Tritylpyridinium tetrakis(pentafluorophenyl)borate as an efficient activator for “constrained-geometry” catalysts in ethylene polymerization
2004
Abstract Ethylene polymerization with linked amido-cyclopentadienyl or “constrained-geometry” titanium catalysts, Ti(η 5 :η 1 -C 5 Me 4 SiMe 2 N t Bu)X 2 (X=Me, Bz, Cl), activated by tritylpyridinium tetrakis(entafluorophenyl)borate, [Ph 3 C(NC 5 H 5 )] [B(C 6 F 5 ) 4 ], and silica-supported tritylpyridinium tetrakis(entafluorophenyl)borate (PySTB) was found to proceed with high activity. 1 H NMR spectra in CD 2 Cl 2 suggest that ([Ti(η 5 :η 1 -C 5 Me 4 ,SiMe 2 N t Bu)Me (NC 5 H 5 )] + is formed as the main cationic species. Using the heterogeneous cocatalyst PySTB in hexane, unexpectedly high ethylene polymerization activity was achieved, giving high molecular weight polyethylenes with exc…
Copolymerization of ethylene with norbornene or 1-octene using supported ionic liquid systems
2016
Copolymerization of ethylene with norbornene (E/NB) and ethylene with 1-octene (E/Oct) is performed using supported ionic liquid (SIL) systems, in which metallocene (Cp2VCl2) or post-metallocene [VCl2(salenCl2)] vanadium catalysts are immobilized in pyridinium chloroaluminate ionic liquid supported on silica. The studied SIL catalysts show higher activities as well as stability than their non-supported analogues. In addition, higher activities and better comonomer incorporation are observed for norbornene (above 30 mol%). The comonomer incorporation has considerable influence on copolymer molecular weight (M w), melting temperature, crystallinity degree, and microstructure of the copolymers…