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See detailAnionic polymerization of pivalolactone initiated by alkali metal alkoxides
Jedlinski, Zbigniew; Kurcok, Piotr; Kowalczuk, Marek et al

in Macromolecules (1995), 28(21), 7276-7280

Polymerization of pivalolactone (alpha,alpha-dimethyl-beta-propiolactone) initiated with alkali metal alkoxides has been studied. It has been revealed that after addition of an alkoxide anion, from the ... [more ▼]

Polymerization of pivalolactone (alpha,alpha-dimethyl-beta-propiolactone) initiated with alkali metal alkoxides has been studied. It has been revealed that after addition of an alkoxide anion, from the initiator, onto the carbonyl carbon atom of the monomer the selective cleavage of the acyl-oxygen bond of the monomer leads to the formation of alkoxide propagating species. Thus, it has been demonstrated that, in contrast to alpha-unsubstituted beta-lactones and higher lactones, the anionic polymerization of pivalolactone proceeds through either alkoxide or carboxylate propagation centers, depending on the nature of initiator used, i.e. an alkoxide or a carboxylate, respectively. In the former case, however, cyclic oligomers are also formed which are unusual in the anionic polymerization of other beta-lactones. This indicates that, whatever the lactone ring size (four-, six-, or seven-membered lactones), intramolecular transesterification reactions can take place if alcoholate ions are propagating species. [less ▲]

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See detailAnionic polymerization of primary acrylates as promoted by Lithium 2-(2-Methoxyethoxy) ethoxide
Nugay, Nihan; Nugay, Turgut; Jérôme, Robert ULg et al

in Journal of Polymer Science. Part A, Polymer Chemistry (1997), 35(2), 361-369

Some primary acrylates, such as methyl, ethyl, n-butyl, and n-nonyl acrylate (MA, EA, nBuA and nNonA, respectively) have been anionically polymerized by using diphenylmethyl lithium (DPMLi) as an ... [more ▼]

Some primary acrylates, such as methyl, ethyl, n-butyl, and n-nonyl acrylate (MA, EA, nBuA and nNonA, respectively) have been anionically polymerized by using diphenylmethyl lithium (DPMLi) as an initiator, in the presence of a chelating - dual ligand, i.e., a polydentate lithium alkoxide, at low temperature. It has been found that lithium 2-(2-methoxyethoxy) ethoxide (LiOEEM) is a very efficient ligand in preventing the anionic polymerization of these monomers from being disturbed by significant secondary transfer and termination reactions. Even for the difficult cases of ethyl and methylacrylate, that approach provides high polymerization yields and low polydispersity, allowing the molecular weight to be predetermined. LiOEEM/initiator molar ratio, solvent polarity, temperature and monomer concentration have proved to be key parameters in the control of the polymerization process. The efficiency of that control is however dependent on the monomer structure and improves with the length of the n-alkyl substituent, i.e., MA < EA < nBuA < nNonA. [less ▲]

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See detailAnionic polymerization of various methacrylates initiated with LiCl-complexed sBuLi
Antoun, S.; Wang, Jin-Shan; Jérôme, Robert ULg et al

in Polymer (1996), 37(25), 5755-5759

A simple alkyl lithium initiator (sBuLi) complexed with LiCl (10 molar equiv.) has been used to initiate the anionic polymerization of various methacrylic monomers, i.e. methyl methacrylate (MMA), tert ... [more ▼]

A simple alkyl lithium initiator (sBuLi) complexed with LiCl (10 molar equiv.) has been used to initiate the anionic polymerization of various methacrylic monomers, i.e. methyl methacrylate (MMA), tert-butyl methacrylate (tBuMA), glycidyl methacrylate (GMA), and dimethyl amino ethyl methacrylate (DMAEMA) in tetrahydrofuran at -78°C. Only the homopolymerization of tBuMA proceeds in a living manner, as evidenced by both the linear plot of experimental molecular weight (Mnexp) vs theoretical ones (Mncal,) (slope % 0.93) and monomer resumption experiments. However, three types of block copolymers, i.e. PtBuMA-b-PMMA, PtBuMA-b-PGMA, PtBuMA-b-PDMAEMA, have been successfully synthesized with a predictable molecular weight, and narrow molecular weight distribution. [less ▲]

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See detailAnionic synthesis of [1,4-poly(diene)-b-syndiotactic poly(methyl methacrylate)] diblock copolymers: 7Li NMR study of the intermediate reaction of lithium poly(diene) anion with 1,1-diphenylethylene
Zune, Catherine; Dubois, Philippe ULg; Jérôme, Robert ULg et al

in Macromolecular Chemistry and Physics (1999), 200(2), 460-467

The end-capping with 1,1-diphenylethylene (DPE) of living 1,4-poly(diene) lithiated anions prepared in cyclohexane (Chx) and toluene is a major but poorly controlled step in the synthesis of syndiotactic ... [more ▼]

The end-capping with 1,1-diphenylethylene (DPE) of living 1,4-poly(diene) lithiated anions prepared in cyclohexane (Chx) and toluene is a major but poorly controlled step in the synthesis of syndiotactic poly(methyl methacrylate) (sPMMA) containing block copolymers. The kinetics of the reaction have been studied by means of 7Li NMR not only in Chx and toluene but also in their mixtures with polar solvents, since the solvent polarity must be increased for MMA to be predominantly converted into sPMMA. Although the addition of a polar solvent (tetrahydrofuran (THF), diethyl ether) to Chx and toluene is known to increase the reactivity of living polymeric anions, contaminating lithium salts, such as lithium hydroxide, slow down the end-capping reaction even when 10 vol.-% polar solvent is added. Moreover, the polymeric diphenylalkyllithium anions are unstable in 1/9 (v/v) THF/Chx mixture, as a result of the nucleophilic attack of THF. On the basis of all these observations, new experimental conditions are proposed for improving the control of the anionic block copolymerization of 1,3-dienes and MMA to yield 1,4-poly(diene) and sPMMA containing block copolymers. [less ▲]

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See detailAnionic synthesis of cyclic anhydride end-capped poly(methyl methacrylate)
Fallais, Isabelle; Pantoustier, Nadège; Devaux, Jacques et al

in Polymer (2000), 41(14), 5535-5539

This paper reports on the anionic synthesis of poly(methyl methacrylate) chains end-capped by cyclic anhydride. The method is based on the chemical derivatization of a precursor tert-butyl diester end ... [more ▼]

This paper reports on the anionic synthesis of poly(methyl methacrylate) chains end-capped by cyclic anhydride. The method is based on the chemical derivatization of a precursor tert-butyl diester end-group. Compared to the thermal modification, which was previously used, this method allows intermolecular coupling and polymer degradation to be avoided. But up to now, the final anhydride content remains moderate and has still to be improved. [less ▲]

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See detailAnionically prepared poly(epsilon-caprolactam-co-epsilon-caprolactone) and poly(epsilon-caprolactam-co-delta-valerolactone) copolymers: thermal and mechanical properties
Toncheva, Natalia ULg; Jérôme, Robert ULg; Mateva, Rosa

in European Polymer Journal (2011), 47(2), 238-247

Thermal and representative physico-mechanical properties of newly prepared poly[(ε-caprolactam)-co-(ε-caprolactone)] and poly[(ε-caprolactam)-co-(δ-valerolactone)] copolymers were studied. The copolymers ... [more ▼]

Thermal and representative physico-mechanical properties of newly prepared poly[(ε-caprolactam)-co-(ε-caprolactone)] and poly[(ε-caprolactam)-co-(δ-valerolactone)] copolymers were studied. The copolymers were synthesized by anionic polymerization of ε-caprolactam activated by isocyanate end-capped oligomeric aliphatic polyesters designated as the macroactivators (MAs). Type, concentration and molecular weight of the MAs were varied, which resulted in copolymers with different structure and properties. The impact of the new MAs used in this study on the glass transition temperature and the melting temperature of poly-ε-caprolactam was investigated by DSC. DMTA was used to analyze the effect of copolymerization on the storage modulus (E′) and tan δ of poly-ε-caprolactam. Conventional and high-resolution TGA data revealed that all the synthesized polyesteramides possess good thermal stability. Mechanical properties were studied by notched impact and tensile testing. According to the experimental data the impact toughness increase with the MA content, being six time higher compared to the poly(ε-caprolactam) in the best situation. Water absorption was also considered in relation to the composition of the copolymers. [less ▲]

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See detailAnisocoria and Cerebro-Vascular Diseases
Martin, Didier ULg

Conference (2006, November 22)

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See detailAnisotropic AC behavior of multifilamentary Bi-2223/Ag tapes
Fagnard, Jean-François ULg; Vanderbemden, Philippe ULg; Cloots, Rudi ULg et al

in IEEE Transactions on Applied Superconductivity (2003), 13(2, Part 3), 2976-2979

In this communication, we report on the anisotropy of the superconducting properties of multifilamentary Bi-based tapes experimentally investigated by AC magnetic susceptibility measurements. The ... [more ▼]

In this communication, we report on the anisotropy of the superconducting properties of multifilamentary Bi-based tapes experimentally investigated by AC magnetic susceptibility measurements. The susceptibility X = X' - jX" was measured using a commercial system and a couple of orthogonal pick-up coils. The X'' vs. temperature curves were shown to exhibit two peaks. The smaller of the peaks, occurring near T = 72 K, was only visible for particular field directions and within a given frequency window. Such results point out the role played by the phase difference between the applied magnetic field and the internal magnetic field seen by the filaments. (C) 2003 IEEE. [less ▲]

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See detailAnisotropic and feature sensitive triangular remeshing using normal lifting
Nivoliers, Vincent; Lévy, Bruno; Geuzaine, Christophe ULg

in Journal of Computational and Applied Mathematics (2015), 289

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See detailAnisotropic avalanches and flux penetration in patterned superconductors
Gheorghe, D. G.; Menghini, M.; Wijngaarden, R. J. et al

in Physica C: Superconductivity (2006), 437-38

Both for a fundamental understanding of the flux penetration process and for technical applications, the role of artificial pinning sites (such as antidots) in superconductors generates a lot of interest ... [more ▼]

Both for a fundamental understanding of the flux penetration process and for technical applications, the role of artificial pinning sites (such as antidots) in superconductors generates a lot of interest. We perform magneto-optical imaging experiments on type-II Pb thin films patterned with square arrays of square antidots and square arrays of rectangular antidots and blind holes. We demonstrate that a square lattice of rectangular antidots can lead to similar anisotropy in flux penetration and critical current as a rectangular lattice of square antidots. In addition we show how thermo-magnetic avalanches can be guided-and hence to a certain extend controlled-by such holes. (c) 2006 Elsevier B.V. All rights reserved. [less ▲]

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See detailAnisotropic behaviour in the magnetic field dependence of the low temperature electrical resistance of calcium-doped lanthanum manganate thin films grown by RF magnetron sputtering
Vertruyen, Bénédicte ULg; Dusoulier, Laurent; Fagnard, Jean-François ULg et al

in Journal of Magnetism and Magnetic Materials (2004), 280(2-3), 264-272

We report about the magnetoresistive properties of calcium-doped lanthanum manganate thin films grown by RF magnetron sputtering on single crystalline LaAiO(3) and MgO substrates. Two orientations of the ... [more ▼]

We report about the magnetoresistive properties of calcium-doped lanthanum manganate thin films grown by RF magnetron sputtering on single crystalline LaAiO(3) and MgO substrates. Two orientations of the magnetic field with respect to the electrical current have been studied: (i) magnetic field in the plane of the film and parallel to the electrical current, and (ii) magnetic field perpendicular to the plane of the film. The film grown on LaAlO3 is characterised by an unusual magneto resistive behaviour when the magnetic field is applied perpendicular to the film plane: the appearance of two bumps in the field dependence of the resistance is shown to be related to the occurrence of anisotropic magneto resistive effects in manganate films. (C) 2004 Elsevier B.V. All rights reserved. [less ▲]

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See detailAnisotropic continuum damage model coupled to viscoplasticity for a pressure dependent alveolar bone remodeling law
Mengoni, Marlène ULg; Ponthot, Jean-Philippe ULg

in National Congress on Theoretical and Applied Mechanics (2009, May)

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See detailAnisotropic damage model for microcracked materials
Levasseur, Séverine ULg

Diverse speeche and writing (2012)

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See detailAnisotropic damage model with initial stresses for microcracked materials
Levasseur, Séverine ULg; Collin, Frédéric ULg; Charlier, Robert ULg et al

in Fifth International Conference on Advanced COmputational Methods in ENgineering (ACOMEN 2011) (2011)

In a recent study (Levasseur et al., 2010), we proposed a class of isotropic damage models which account for initial stresses. The present paper extends this approach to anisotropic damage due to growth ... [more ▼]

In a recent study (Levasseur et al., 2010), we proposed a class of isotropic damage models which account for initial stresses. The present paper extends this approach to anisotropic damage due to growth of an arbitrarily penny-shaped microcracks system. The basic principle of the upscaling technique in the presence of initial stress is first recalled. Then, we derive a closed-form expression of the elastic energy potential corresponding to a system of arbitrarily oriented microcracks. Thanks to the investigation of the influence of initial stresses on the material response under non monotonous loading paths, it is shown how the coupling between initial stresses and damage is strongly dependent of the microcracks density and orientation. In case of a particular distribution of microcracks orientation, described by a second order damage tensor, this model corresponds to a generalization of the macroscopic damage model of Halm and Dragon (1996), for which a physically-based interpretation can be proposed. [less ▲]

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See detailAnisotropic elasto-plastic finite element analysis using a stress-strain interpolation method based on a polycrystalline model
Habraken, Anne ULg; Duchene, Laurent ULg

in International Journal of Plasticity (2004), 20(Issue 8-9), 1525-1560

This paper describes a stress–strain interpolation method to model the macroscopic anisotropic elasto-plastic behavior of polycrystalline materials. Accurate analytical descriptions of yield loci derived ... [more ▼]

This paper describes a stress–strain interpolation method to model the macroscopic anisotropic elasto-plastic behavior of polycrystalline materials. Accurate analytical descriptions of yield loci derived from crystallographic texture [Int. J. Plasticity 19 (2003) 647; J. Phys. IV France 105 (2003) 39] are an interesting alternative to finite element models, where the macroscopic stress is provided by an averaging of microscopic stresses computed on a set of representative crystallites [Acta Metal 22 (1985) 923; Int. J. Plasticity 5 (1989) 67]. The parameters of the analytical functions modeling the yield locus are identified by comparison with a high number of stress tensors computed, for instance, by the well-known Taylor model [J. Inst. Metal 62 (1938) 307]. This identification method depends on the crystallographic texture and should be applied each time that the plastic strain has induced a significant texture evolution. The stress–strain interpolation method accurately describes the anisotropic material behavior in a narrow stress direction defined by only five stress points. The cost of texture updating is then greatly reduced compared to a full analytical function of the yield locus. After the mathematical description of the stress–strain interpolation method, its validity is demonstrated on two non-radial strain paths. The simulations of a deep drawing experiment allow comparing model predictions and measurements. Accuracy and CPU time of the interpolation stress–strain method are judged against two other models, respectively based on a complete analytical yield locus and on the averaging of crystallite stresses. [less ▲]

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See detailAnisotropic elastoplastic model based on texture
Habraken, Anne ULg; Duchene, Laurent ULg; Godinas, André et al

in Handbook of materials behavior models (2001)

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See detailAnisotropic Elastoplastic Model Based on Texture
Habraken, Anne ULg

in Lemaitre Handbook of Materials Behavior Models (2001)

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See detailAnisotropic field percolation and high current density in 2212 Bi-based substituted with Dy bulk magnetically textured composite ceramics
Vanderbemden, Philippe ULg; Vanderschueren, Hyacinthe ULg; Stassen, Sophie et al

in Matsushita, T.; Yamafuji, K. (Eds.) Proceedings of the 8th International Workshop on Critical Currents in Superconductors (1996)

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See detailAnisotropic hydromechancial modelling of HGA field-scale experiment in Opalinus Clay
Levasseur, Séverine ULg; Collin, Frédéric ULg; François, Bertrand et al

Conference (2012)

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See detailAnisotropic Orientations of Polarisations from quasar light
Pelgrims, Vincent ULg

Conference (2013, September)

Presentation of the foundations of a new statistical test dedicated to the polarisation orientations analysis.

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