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See detailLes animaux, malades de l’homme, en collaboration avec Chris Herzfeld (U.L.B.) le 20 avril 2001.
Strivay, Lucienne ULg

Conference given outside the academic context (2001)

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See detailAnimer, bricoler, secouer. L’art loufoque et poétique de Patar et Aubier
Tomasovic, Dick ULg

Article for general public (2014)

Commentaire et analyse du travail des animateurs Vincent Patar et Stéphane Aubier.

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See detailAnion translocators in rat-heart mitochondria
Sluse, Francis ULg; Meijer, Alfred; Tager, Joseph

in FEBS Letters (1971), 18

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See detailAnionic block copolymerization of 4-vinylpyridine and tert-butyl methacrylate at "elevated" temperature : influence of various additives on the molecular parameters
Creutz, Serge; Teyssié, Philippe; Jérôme, Robert ULg

in Macromolecules (1997), 30(19), 5596-5601

The living anionic polymerization of 4-vinylpyridine (4VP) in 9/1 pyridine/THF at 0 °C has been reported lately (Creutz, S.; Teyssié, Ph.; Jérôme, R. Macromolecules 1997, 30, 1). The success of its block ... [more ▼]

The living anionic polymerization of 4-vinylpyridine (4VP) in 9/1 pyridine/THF at 0 °C has been reported lately (Creutz, S.; Teyssié, Ph.; Jérôme, R. Macromolecules 1997, 30, 1). The success of its block copolymerization with tert-butyl methacrylate (tBMA) has been shown to be dependent on the addition mode, highlighting the difference in reactivity between the two monomers. Moreover, the (co)solvent also strongly influences the fate of that copolymerization. Thus, the impact of various (co)solvents and additives has been investigated more thoroughly, revealing the interesting possibility of modifying the apparent relative reactivities of these two monomers. [less ▲]

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See detailAn anionic class III peroxidase from zucchini may regulate hypocotyl elongation through its auxin oxidase activity.
Cosio, Claudia; Vuillemin, Loic; De Meyer, Mireille et al

in Planta (2009)

The high number of peroxidase genes explains the description of numerous physiological functions and the fact that the in planta function of a single isoform has never been characterized yet. We analyzed ... [more ▼]

The high number of peroxidase genes explains the description of numerous physiological functions and the fact that the in planta function of a single isoform has never been characterized yet. We analyzed in transgenic Arabidopsis thaliana the localization of a zucchini isoperoxidase (APRX), previously purified thanks to its pectin binding ability. We confirmed that the protein is localized near the cell wall, mainly produced in the elongation area of the hypocotyls and respond to exogenous auxin. In addition, the ectopic overexpression of APRX induced changes in growth pattern and a significant reduction of endogenous indole-3-acetic acid (IAA) level. In agreement with these observations APRX showed an elevated in vitro auxin oxidase activity. We propose that APRX participates in the negative feedback regulation of auxin level and consequently terminates the hypocotyl elongation process. [less ▲]

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See detailAnionic flow polymerizations toward functional polyphosphoesters in microreactors: Polymerization and UV-modification
Baeten, Evelien; Vanslambrouck, Stéphanie; Jérôme, Christine ULg et al

in European Polymer Journal (2016), 80

The polymerization of cyclic phosphates to poly(phosphoester)s, PPEs, is optimized for chip- based microreactors under continuous flow conditions. The anionic ring-opening polymerization of 2-isobutyoxy-2 ... [more ▼]

The polymerization of cyclic phosphates to poly(phosphoester)s, PPEs, is optimized for chip- based microreactors under continuous flow conditions. The anionic ring-opening polymerization of 2-isobutyoxy-2-oxo-1,3,2-dioxaphospholane (iBP) via the use of two organocatalytic systems allowed to polymerize to nearly quantitative monomer conversion within 10 or 3 minutes, respectively at a reaction temperature of 40 °C. Further, the optimized polymerization protocol was applied to 2-butenoxy-2-oxo-1,3,2-dioxaphospholane (BP) which yields a polymer that carries an alkene functionality per monomer repeating unit. This material can be postmodified in an UV-induced radical thiol-ene reaction, which was also shown to proceed with very high efficiency under UV-flow conditions. Eventually, both reactions were coupled in a two-stage reactor setup, showing that the thermally-activated polymerization can be coupled with high efficiency to the UV-activated post-polymerization modification reaction. The introduced reactor setup can in the future be used to produce and screen a broad variety of functional PPE materials with various functionalities and physical properties. [less ▲]

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See detailAnionic polymerisation of methyl methacrylate with complex initiator system
Nugay, Turgut; Nugay, Nihan; Jérôme, Robert ULg

in Polymer Bulletin (2002), 48(6), 457-462

Polymerisation of methyl methacrylate was conducted by using alkyl lithium/dimethylsulfoxide (DMSO) system as initiator in toluene. A special attention was focused on using some lithium polyetheralkoxides ... [more ▼]

Polymerisation of methyl methacrylate was conducted by using alkyl lithium/dimethylsulfoxide (DMSO) system as initiator in toluene. A special attention was focused on using some lithium polyetheralkoxides as polymerisation promoters at ambient temperatures. Poly(methyl methacrylate) samples were characterized with Gel Permeation Chromatography (GPC), Nuclear Magnetic Resonance Spectroscopy (H-1 NMR) and Differential Scanning Calorimetry (DSC). The positive effect of the mu/sigma type ligands such as lithium 2-(2-methoxyethoxy)ethoxide (LiOEEM), 2-(methoxy)ethoxide (LiOEM) on controlling the living character, molecular weight, stereo regularity and the yield of the produced polymers was demonstrated. It has been found that this approach provided high polymerisation yields and low polydispersity but low initiator efficiency. [less ▲]

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See detailAnionic polymerization of (meth)acrylic monomers. 12. Efect of lithium chloride on the stereochemistry on the anionic polymerization of methyl methacrylate in THF and in a 9/1 toluene/THF mixture
Wang, Jin-Shan; Jérôme, Robert ULg; Warin, Roger et al

in Macromolecules (1993), 26(22), 5984-5990

The effect of LiCl on the stereochemistry of the anionic polymerization of methyl methacrylate in the presence of a lithium counterion at -78-degrees-C in THF and in a 9/1 toluene/THF mixture, has been ... [more ▼]

The effect of LiCl on the stereochemistry of the anionic polymerization of methyl methacrylate in the presence of a lithium counterion at -78-degrees-C in THF and in a 9/1 toluene/THF mixture, has been studied by C-13 and H-1 NMR spectroscopy. It has been found that LiCl has an important effect on the E/Z ratio of the living chain ends in THF, in contrast to the main-chain tacticity. In contrast, LiCl has a significant influence on the stereoregularity of the anionic polymerization of MMA in a 9/1 toluene/THF mixture. When the LiCl/initiator molar ratio is increased, the syndiotactic placements (rr) are favored at the expense of the isotactic ones (mm). This effect can be accounted for by a multistate propagating mechanism controlled by association/complexation equilibria among associated, nonassociated, and LiCl-complexed species. These association/complexation equilbria, which were originally proposed by Muller, appear to have a decisive effect not only on the livingness (molecular weight distribution (MWD)) but also on the stereochemistry of the anionic polymerization of MMA in a 9/1 toluene/THF mixture at -78-degrees-C, confirming the involvement of the ligand in propagation control. [less ▲]

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See detailAnionic polymerization of (meth)acrylic monomers. 22. Anionic polymerization of tert-butyl methacrylate in toluene/THF mixtures : a preliminary approach to the role of solvation/ligation equilibria
Wang, Jin-Shan; Zhang, Hong ULg; Jérôme, Robert ULg et al

in Macromolecules (1995), 28(6), 1758-1764

Although the anionic polymerization of tert-butyl methacrylate (tBMA) induces a narrow and unimodal molecular weight distribution (MWD) when performed in either pure THF or pure toluene at -78 degrees C ... [more ▼]

Although the anionic polymerization of tert-butyl methacrylate (tBMA) induces a narrow and unimodal molecular weight distribution (MWD) when performed in either pure THF or pure toluene at -78 degrees C in the presence of a Lithium counterion, that in THF/toluene mixtures, keeping other conditions unchanged, surprisingly gives rise to broad bi- and even multimodal MWD's. Moreover, with increasing polymerization temperature from -78 to 0 degrees C, that multimodal MWD gets narrower, atypical of termination reactions, and indeed at 0 degrees C, a very narrow unimodal MWD is again obtained. These results have been satisfactorily interpreted in terms of a multiple solvation equilibria mechanism: there coexist several types of THF-solvated and nonsolvated active species and the exchange among them is slow at -78 degrees C but fast at 0 degrees C compared to the monomer propagation rate, thus resulting in a multimodal MWD in the former case and a narrow one in the latter. Furthermore, this solvation mechanism also dominates the stereoregulation of the tBuMA polymerization in mixed solvent. It has indeed been demonstrated that addition of various types of ligands, i.e., lithium chloride (LiCl) and lithium tert-butoxide (LiOtBu) (both mu-ligands), 12-crown-4 (12CE4) and cryptand 211 (K211) (both sigma-chelating ligands), and Lithium 2-(2-methoxyethoxy)ethoxide (LiOE(2)M) (a mu/sigma dual type of ligand), affects the tBMA anionic polymerization in a way which can be accounted for by these so-called solvation/ligation multiple equilibria among THF-nonsolvated, THF-solvated, and Ligated ion pairs. Once again, the fact that, in comparison with 12CE4 and LiOtBu, such ligands as LiOE(2)M, K211, and LiCl can effectively promote a much narrower MWD is nicely related to their high propensity to coordinate with a lithium ester enolate and at the same time to either promote a fast-exchanging ligation equilibrium or form a single type of active complex, in good agreement with the NMR investigation of corresponding model systems as previously reported by us. [less ▲]

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See detailAnionic polymerization of (meth)acrylic monomers. IV. Effect of lithium salts as ligands on the "living" polymerization of methyl methacrylate using monofunctional initiators
Varshney, Sunil K; Hautekeer, J. P.; Fayt, Roger et al

in Macromolecules (1990), 23

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See detailAnionic polymerization of (meth)acrylic monomers: anionic polymerization of tert-butyl methacrylate in toluene
Zune, Catherine; Dubois, Philippe ULg; Jérôme, Robert ULg

in Polymer International (1999), 48(7), 565-570

The anionic polymerization of tBMA initiated by an organolithium compound in toluene at low temperature (-78 °C and 0 °C) has been revisited. Under these experimental conditions, no livingness is reported ... [more ▼]

The anionic polymerization of tBMA initiated by an organolithium compound in toluene at low temperature (-78 °C and 0 °C) has been revisited. Under these experimental conditions, no livingness is reported, consistently with formation of an important fraction of oligomers (Mn = 650). [less ▲]

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See detailAnionic polymerization of acrylic monomers. 10. 13C and 7Li NMR studies on the monomeric model of living poly(methyl)methacrylate)
Wang, Jin-Shan; Jérôme, Robert ULg; Warin, R. et al

in Macromolecules (1993), 26(6), 1402-1406

A monomeric model structurally comparable to the active end of a living poly(methyl methacrylate) (PMMA), i.e., a methyl α-lithioisobutyrate (MIBLi)/THF solution, was studied by both Li-7 and C-13 NMR. It ... [more ▼]

A monomeric model structurally comparable to the active end of a living poly(methyl methacrylate) (PMMA), i.e., a methyl α-lithioisobutyrate (MIBLi)/THF solution, was studied by both Li-7 and C-13 NMR. It has been shown that two different coordination aggregates exist in a MEBLi/THF solution. That situation corresponds to a slow exchange process between tetramer and dimer, i.e. the later being favored by a decrease in temperature or concentration. Such an equilibrium is characterized with ΔH = -2.1 kcal/mol and ΔS = -13.7 cal/mol.K by means of Li-7 NMR. Again, C-13 NMR results obtained suggest that a MIBLi/THF solution displays a charge-delocalized character, which is different from a O-Li-bonded bonded structure in solid state established by crystal analyses of several similar ester enolates. [less ▲]

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See detailAnionic polymerization of acrylic monomers. 11 NMR investigation of the mixed complexation of methyl α-lithioisobutyrate and lithium chloride
Wang, Jin-Shan; Warin, R.; Jérôme, Robert ULg et al

in Macromolecules (1993), 26

Solutions of methyl α-lithioisobutyrate (MIBLi) in THF added with various amounts of lithium chloride (LiCl) have been analyzed by Li-7 NMR spectroscopy in a wide range of temperatures. Although below ca ... [more ▼]

Solutions of methyl α-lithioisobutyrate (MIBLi) in THF added with various amounts of lithium chloride (LiCl) have been analyzed by Li-7 NMR spectroscopy in a wide range of temperatures. Although below ca. 205 K tetramers of MIBLi have been reported to be in equilibrium with dimers, 1/1 and 2/1 LiCl/MIBLi mixed complexes instantaneously form upon the addition of 1 and 2 mol equiv of LiCl, respectively. Further addition of LiCl more likely promotes the formation of a less stable 3/1 complex. Both 1/1 and 2/1 adducts are stable between -80-degrees-C and at least +12-degrees-C. From C-13 NMR spectroscopy, it appears that the addition of an equimolar amount of LiCl to the MIBLi solution in THF is at the origin of a ca. 7.0 ppm upfield shift of the metalated α-carbon compared to the tetrameric MIBLi species and a ca. 1.0 ppm downfield shift with respect to the dimeric MIBLi. However, the charge distribution over the carbanion does not change anymore when the amount of LiCl exceeds 1 mol equiv. In contrast to nonligated MEBLi, the OR group has a considerable rotational freedom in LiCl-modified MIBLi. A comparison of the structure and dynamics of the LiCl-modified MIBLi species in THF at 197 K with the characteristic features of the anionic polymerization of MMA under the same conditions suggests that the formation of one type of LiCl-complexed species has a decisive effect on the control of the living polymerization of MMA. This conclusion is in agreement with a kinetic study carried out by Muller for the same system. [less ▲]

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See detailAnionic polymerization of acrylic monomers. 13. Carbon-13 NMR characterization of the mixed complexation of methyl α-lithioisobutyrate by lithium tert-butyoxide in tetrahydrofuran
Wang, Jin-Shan; Jérôme, Robert ULg; Warin, Roger et al

in Macromolecules (1994), 27(24), 1691-1696

The mixed complexation of methyl alpha-lithioisobutyrate(MIBLi)(a monomeric model structurally corresponding to the living end of PMMA-Li+) with lithium tert-butoxide (LiOtBu) in THF has been studied for ... [more ▼]

The mixed complexation of methyl alpha-lithioisobutyrate(MIBLi)(a monomeric model structurally corresponding to the living end of PMMA-Li+) with lithium tert-butoxide (LiOtBu) in THF has been studied for the first time by using C-13 NMR spectroscopy. It is shown that LiOtBu, like LiCl, is very effective in coordinating with MIBLi tetramer in THF, incrementally replacing MIBLi with the formation of other tetrameric complexes, MIBxLi4(OtBu)4-x (x = 1-3). Complextion of MIBLi by LiOtBu induces a shielding C-13 shift of the MIBLi C(alpha) resonance, which might suggest that lithium cations associated with the electron-rich ligands, i.e., LiOtBu, can also form weaker bonds with the carbonyl oxygen of MIBLi (i.e., mu-type complexes), thereby decreasing the localization of the negative charge on that latter atom. In comparison with LiCl, one of the most significant features is that only one single type of species results from mixed complexation of MIBLi and LiCl at LiCl/MIBLi = 1, 2, and greater-than-or-equal-to 3, respectively, at low temperature, whereas several LiOtBu-complexed species may coexist, whatever the LiOtBu/MIBLi ratio; furthermore, their exchange is found to be very slow at a temperature as high as 0-degrees-C. Tentatively, this striking feature may explain nicely the large difference in molecular weight distribution of poly(meth)acrylates anionically prepared in the presence of LiOtBu and LiCl, respectively. [less ▲]

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See detailAnionic polymerization of acrylic monomers. 14. Carbon-13 and lithium-7 NMR characterization of the complexation of methyl α-lithioisobutyrate with various lithium cation-binding ligands in tetrahydrofuran
Wang, Jin-Shan; Jérôme, Robert ULg; Warin, R. et al

in Macromolecules (1994), 27(12), 3376-3382

The aggregation equilibrium and electronic structure of methyl alpha-lithioisobutyrate (MIBLi), a monomeric model structurally corresponding to a living poly(methyl methacrylate) chain end associated with ... [more ▼]

The aggregation equilibrium and electronic structure of methyl alpha-lithioisobutyrate (MIBLi), a monomeric model structurally corresponding to a living poly(methyl methacrylate) chain end associated with a lithium countercation, has been examined by Li-7 and/or C-13 NMR spectroscopy in tetrahydrofuran (THF) in the presence of various lithium cation-binding ligands. The addition of dimethoxyethane (DME), triglyme (glyme-3),12-crown-4 (12-CE-4), and hexamethylphosphoric triamide (HMPA) to coexisting tetrameric and dimeric MIBLi in THF induces an increase in dimeric population in the order DME < glyme-3 < 12-CE-4 <HMPA. That order corresponds to an increasing strength of complexation between MIBLi (lithium cation) and the (solvating) ligands For either tetrameric or dimeric species, moreover, the negative charge distribution around MIBLi does not seem to be significantly modified due to the presence of these complexing agents. In striking contrast, complexation of MIBLi by cryptand 211 (K211) does shift the equilibrium between tetramer and dimer toward the formation of a single monomeric K211-complexed species, which gives rise to ca. 13 and 5 ppm upfield shifts at C(alpha) in the C-13 NMR spectra, compared to tetrameric and dimeric species, respectively. The effect of 12-CE-4/K211 on the original aggretation equilbrium for MIBLi in THF nicely explains the significantly different MWD of PMMA anionically prepared in the presence of each of these ligands. [less ▲]

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See detailAnionic polymerization of acrylic monomers. 15. Living anionic copolymerization of mixtures of methyl metacrylate and tert-butyl acrylate as promoted by dibenzo-18-crown-6
Wang, Jin-Shan; Jérôme, Robert ULg; Bayard, Philippe et al

in Macromolecules (1994), 27(16), 4615-4620

Although mu-coordinating ligands such as LiCl are effective in promoting the well-controlled living anionic block copolymerization of methyl methacrylate (MMA) and tert-butyl acrylate (tBuA), whichever ... [more ▼]

Although mu-coordinating ligands such as LiCl are effective in promoting the well-controlled living anionic block copolymerization of methyl methacrylate (MMA) and tert-butyl acrylate (tBuA), whichever monomer is first polymerized, it has been previously shown that a copolymerization of mixtures of these two monomers does not proceed as expected, giving poor results in terms of both conversion and molecular weight distribution: that was accounted for by the easy back-biting nucleophilic attack of a highly sensitive methyl ester group by a moderately hindered PtBuA anion. It is now reported that such a situation can be completely modified, when a cation-binding sigma-ligand, i.e., dibenzo-18-CE-6, is used in chelating a sodium counterion and surrounding it with a steric barrier, blocking a large enough space area around the ion pair. In fact, a living copolymerization process of mixtures of MMA and tBuA prevails in THF at -78-degrees-C, in the presence of that Na+/DB-18-CE-6 system. The living copolymer is found, although in a relatively small extent, to be of a statistical type rather than a blocky one or a mixture of two corresponding homopolymers. Furthermore, using the extended Kelen-Tudos method, the monomer reactivity ratios are determined to be r(MMA) = 0.02 and r(tBuA) = 8.81. [less ▲]

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See detailAnionic polymerization of acrylic monomers. 17. Ligated anionic living polymerization of 2-ethylhexyl acrylate as promoted by polydentate lithium alkoxides
Wang, Jin-Shan; Bayard, Philippe; Jérôme, Robert ULg et al

in Macromolecules (1994), 27(18), 4890-4895

Different initiators combined with a new family of mu/sigma dual ligands, i.e., polydentate alkoxides, were used to initiate the anionic polymerization of 2-ethylhexyl acrylate (2EtHA) at low temperatures ... [more ▼]

Different initiators combined with a new family of mu/sigma dual ligands, i.e., polydentate alkoxides, were used to initiate the anionic polymerization of 2-ethylhexyl acrylate (2EtHA) at low temperatures. It has been found that lithium 2(2-methoxyethoxy) ethoxide (LiOEEM) is the most efficient mu/sigma ligand in promoting a living polymerization of that monomer. Although LiOEEM gives rise to a molecularly well-controlled P2EtHA at -78 degrees C in a 9/1 toluene/THF mixture, i.e., quantitative yield, high initiator efficiency (>90%), and narrow molecular weight distribution (M(w)/M(n) down to 1.05), two-step monomer resumption experiments always lead to a bimodal distribution, suggesting that the LiOEEM-complexed P2EtHA anions are not stable. Nevertheless, a perfectly living 2EtHA anionic polymerization process has been obtained at -100 degrees C, keeping other conditions unchanged. In comparison with other types of ligands, such as LiCl and LiOtBu (both mu-ligands) and DB18CE6 and K222 (both sigma-ligands), it has been further demonstrated that the formation of a stable and bulky active complex is at the origin of the anionic living polymerization of 2EtHA, in agreement with our findings in the case of anionic statistical copolymerization of methacrylate and acrylate. [less ▲]

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See detailAnionic polymerization of acrylic monomers. 18. NMR characterization of a unique complex between lithium 2-(2-methoxyethoxy) ethoxide and methyl α-lithioisobutyrate
Wang, Jin-Shan; Jérôme, Robert ULg; Teyssié, Philippe

in Macromolecules (1994), 27(18), 4896-4901

A unique ligand-promoted-loose mixed complex MIB-(Li-3(OEEM)(2))(+) has been characterized for the first time by means of NMR spectroscopy in solution. This new complex, which is a dual mu/sigma one, is ... [more ▼]

A unique ligand-promoted-loose mixed complex MIB-(Li-3(OEEM)(2))(+) has been characterized for the first time by means of NMR spectroscopy in solution. This new complex, which is a dual mu/sigma one, is obviously different from either a simple tight mu-mixed complex, such as nMIBLi.mX (X = Cl or OtBu), or a sigma-cation-binding one with mole charge separation, such as K211/MIBLi. It originates from a simultaneous dual complexation (mu/sigma) of MIBLi by both the lithium alkoxide (mu-mixed complexation) and the chelating polyether components (sigma-cation-binding complexation) of LiOEEM. Furthermore, it has been demonstrated; that, whichever the solvent, i.e., toluene, a 9/1 toluene/THF mixture, or THF, complexation of MIBLi by greater than or equal to 2 mol equiv of LiOEEM produces the same type of complex, i.e., MIB-(Li-3(OEEM)(2))(+), suggesting that, in this strong complex, the lithium cations are strongly coordinated by the ligand. [less ▲]

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