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See detailCoastal-open ocean exchange in the Black Sea: Observations and modelling
Stanev, Emil; Beckers, Jean-Marie ULg; Lancelot, Christiane et al

in Estuarine Coastal & Shelf Science (2002), 54(3), 601-620

The interaction between physical and biological processes in the areas of continental margins governs the variability of ecosystems. The complexity of processes in these areas requires detailed studies ... [more ▼]

The interaction between physical and biological processes in the areas of continental margins governs the variability of ecosystems. The complexity of processes in these areas requires detailed studies combining modelling and surveying efforts. One promising step in this direction was undertaken in the framework of the EROS 21 project, focusing on the shelf part of the north-western Black Sea. In the present paper, we focus on the results of physical studies aiming to improve the understanding of the fundamental exchange processes in the ocean margins, as well as to quantify some of them in the Black Sea. We illustrate the capabilities of circulation models to reproduce physical processes with different time- and space-scales: coastal waves, internal waves, baroclinic Rossby and topographic waves. Another class of important phenomena in the coastal zone is associated with convection. Sources at the sea surface and in the outflow areas give rise to plume dynamics that play a crucial role in the vertical mixing and provide the mechanism for water-mass formation. Most of the results are illustrated for the shelf part of the Black Sea. The verification of simulations is performed by comparison with survey data, altimeter data from the Topex/Poseidon mission and radiotracer observations. The latter, in combination with simulations from circulation models, are used to trace the penetration of tracers into the intermediate and deep layers. We show that although most Sr-90 is introduced by river runoff, large amounts of this signal penetrate the halocline in the Bosphorus Straits area and along the southern coast. Another important fraction of the river water penetrates the intermediate layers at the shelf edge in the north-western Black Sea. (C) 2002 Elsevier Science Ltd. All rights reserved. [less ▲]

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See detailCoating of gold nanoparticles by thermosensitive poly(N-isopropylacrylamide) end-capped by biotin
Aqil, Abdelhafid ULg; Qiu, Hongjin; Greisch, Jean-François ULg et al

in Polymer (2008), 49(5), 1145-1153

Gold nanoparticles (NPs) were prepared by reduction of HAuCl4 in aqueous solution and stabilized by poly(N-isopropylacrylamide) (PNIPAM). PNIPAM was prepared by two distinct routes: (i) conventional free ... [more ▼]

Gold nanoparticles (NPs) were prepared by reduction of HAuCl4 in aqueous solution and stabilized by poly(N-isopropylacrylamide) (PNIPAM). PNIPAM was prepared by two distinct routes: (i) conventional free-radical polymerization leading to polymer without any reactive end-group, and (ii) Reversible Addition–Fragmentation chain Transfer (RAFT) polymerization with 2-dodecylsulfanylthiocarbonylsulfanyl-2-methyl propionic acid (DMP) as a RAFT agent. PNIPAM with low polydispersity was then end-capped by an α-carboxylic acid and an ω-trithiocarbonate that was converted into an ω-thiol upon hydrolysis. This hetero-telechelic polymer was analyzed by mass spectroscopy, size exclusion chromatography (SEC) and 1H NMR. Even without thiol end-group, known for chemisorption onto gold, PNIPAM was effective in stabilizing gold NPs (1–5 nm). The thermosensitivity of PNIPAM at the surface of gold NPs was, however, dependent on the molecular weight of the chains. Finally, the α-carboxyl end-group of PNIPAM was used to anchor biotin, which is indeed known for complexation with avidin, which is a possible strategy for the coated gold NPs to be involved as building blocks in supramolecular assemblies. TEM and UV–vis spectroscopy were used to characterize the gold nanoparticles. [less ▲]

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See detailCobalt mediated radical coupling (CMRC) : an unusual route to midchain-functionalized symmetrical macromolecules
Debuigne, Antoine ULg; Poli, Rinaldo; De Winter, Julien et al

in Chemistry : A European Journal (2010), 16(5), 1799-1811

Cobalt-mediated radical coupling (CMRC) is a straightforward approach to the synthesis of symmetrical macromolecules that relies on the addition of 1,3-diene compounds onto polymer precursors preformed by ... [more ▼]

Cobalt-mediated radical coupling (CMRC) is a straightforward approach to the synthesis of symmetrical macromolecules that relies on the addition of 1,3-diene compounds onto polymer precursors preformed by cobalt-mediated radical polymerization (CMRP). Mechanistic features that make this process so efficient for radical polymer coupling are reported here. The mechanism was established on the basis of NMR spectroscopy and MALDI-MS analyses of the coupling product and corroborated by DFT calculations. A key feature of CMRC is the preferential insertion of two diene units in the middle of the chain of the coupling product mainly according to a trans-1,4-addition pathway. The large tolerance of CMRC towards the diene structure is demonstrated and the impact of this new coupling method on macromolecular engineering is discussed, especially for midchain functionalization of polymers. It is worth noting that the interest in CMRC goes beyond the field of polymer chemistry, since it constitutes a novel carbon-carbon bond formation method that could be applied to small organic molecules. [less ▲]

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See detailCobalt mediated radical polymerization (CMRP) using bis(acetylacetonato)cobalt(II): a unique tool for controlling the radical polymerization of conjugated and unconjugated vinyl monomers
Hurtgen, Marie ULg; Debuigne, Antoine ULg; Jérôme, Christine ULg et al

Poster (2009, September 17)

Cobalt-Mediated Radical Polymerization (CMRP) imparts a high level of control on the polymerization of acrylic and vinylic esters, acrylic acid and acrylonitrile. However, each class of monomers appears ... [more ▼]

Cobalt-Mediated Radical Polymerization (CMRP) imparts a high level of control on the polymerization of acrylic and vinylic esters, acrylic acid and acrylonitrile. However, each class of monomers appears to be controlled by one class of cobalt complexes. For example, the polymerization of acrylates and acrylic acid is mediated by cobalt porphyrin complexes while vinyl acetate (VAc) and acrylonitrile are efficiently controlled by bis(acetylacetonato)cobalt(II) (Co(acac)2). Therefore, a challenging issue in CMRP remains to broaden the range of monomers that can be controlled by the same cobalt complex. Recently, the controlled random copolymerization of butyl acrylate (BuA) with VAc was performed using the conventional V-70/Co(acac)2 CMRP system, but the homopolymerization of BuA remained uncontrolled. In this work, we used a new alkylcobalt(III) adduct to initiate and control the copolymerization of BuA with VAc. This achievement resulted in a significant improvement over the V-70/Co(acac)2 pair regarding the molecular weight control and the polydispersity indexes. Moreover, for the first time, the alkylcobalt(III) adduct was also efficient in controlling the homopolymerization of BuA and yielded low polydispersity PBuA even in the absence of VAc. These results indicate that Co(acac)2 is a versatile mediator for the CMRP of both unconjugated vinyl monomers (VAc, N-vinylpyrrolidone) and conjugated monomers such as acrylates. It gives access to copolymers that cannot be prepared by other controlled radical polymerization techniques. [less ▲]

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See detailCobalt(II) complexes as controlling agents for the radical polymerization of vinyl monomers
Debuigne, Antoine ULg; Sciannaméa, Valérie; Piette, Yasmine ULg et al

Poster (2007, August 31)

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See detailCobalt-assisted synthesis of novel block copolymers
Debuigne, Antoine ULg

Scientific conference (2009, February 05)

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See detailCobalt-mediated radical (co)polymerization of vinyl chloride and vinyl acetate
Piette, Yasmine; Debuigne, Antoine ULg; Jérôme, Christine ULg et al

in Polymer Chemistry (2012), 3(10), 2880-2891

The cobalt mediated radical polymerization (CMRP) of vinyl chloride (VC) in the presence of bis(acetylacetonato)cobalt(II) (Co(acac)2) as a controlling agent is presented for the first time. Using an ... [more ▼]

The cobalt mediated radical polymerization (CMRP) of vinyl chloride (VC) in the presence of bis(acetylacetonato)cobalt(II) (Co(acac)2) as a controlling agent is presented for the first time. Using an alkyl-Co(III) compound (R0–(CH2–CHOAc)<4–Co(acac)2; R0 = (H3C)2(OCH3)C–CH2–C(CH3)(CN)–) as an initiator, the bulk polymerization under non-isotherm conditions is controlled. 1H NMR spectra of the resulting PVC show that the CMRP process does not significantly affect the level of defects compared to a PVC prepared by a conventional free radical polymerization at the same temperature. Using the same alkyl-cobalt(III) compound, the copolymerization of VC and VAc is controlled at 40 °C provided that enough VAc (about 40 mol%) is present in the polymerization medium to moderate the VC polymerization. In line with reactivity ratios, VC is preferentially incorporated in the polymer at the early stages of the polymerization, leading to copolymers with a high VC content at moderate conversions. This is the first report of a CMRP of VC and of the synthesis of well-defined statistical PVC-co-PVAc copolymers by this technique. [less ▲]

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See detailCobalt-mediated radical copolymerization of conjugated and non-conjugated monomers
Hurtgen, Marie ULg; Debuigne, Antoine ULg; Fustin, Charles-André et al

in Polymer Preprints (2011), 52(2), 626-627

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See detailCobalt-mediated radical polymerization
Debuigne, Antoine ULg; Jérôme, Robert ULg; Jérôme, Christine ULg et al

in Schlüter, Dieter A.; Hawker, Craig; Sakamoto, Junji (Eds.) Synthesis of polymers: new structures and methods (2012)

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See detailCobalt-mediated radical polymerization (CMRP) and coupling reaction (CMRC): mechanistic advances ans synthetic opportunities
Debuigne, Antoine ULg; Poli, Rinaldo; De Winter, Julien et al

Poster (2009, December 14)

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See detailCobalt-mediated radical polymerization (CMRP) of vinyl acetate initiated by redox systems: Toward the scale-up of CMRP
Bryaskova, Rayna ULg; Detrembleur, Christophe ULg; Debuigne, Antoine ULg et al

in Macromolecules (2006), 39(24), 8263-8268

A redox initiating system was developed in order to bypass 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (V70) as the initiator of the cobalt-mediated radical polymerization (CMRP) of vinyl acetate ... [more ▼]

A redox initiating system was developed in order to bypass 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (V70) as the initiator of the cobalt-mediated radical polymerization (CMRP) of vinyl acetate (VAc) in the presence of cobalt(II) acetylacetonate (Co(acac)(2)). It is indeed a problem to stock up with V70 because of needed storage at -20 degrees C during transportation. This paper reports on the controlled CMRP of VAc initiated by ascorbic acid combined with either lauroyl peroxide or benzoyl peroxide at 30 degrees C. Substitution of citric acid for ascorbic acid results in faster polymerization whereas the polymerization control is maintained. All these improvements facilitate the implementation of the vinyl acetate CMRP and open the door to the scale-up of the process. [less ▲]

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See detailCobalt-mediated radical polymerization of acrylonitrile: Kinetics investigations and DFT calculations
Debuigne, Antoine ULg; Michaux, Catherine; Jérôme, Christine ULg et al

in Chemistry : A European Journal (2008), 14(25), 7623-7637

The successful controlled homopolymerization of acrylonitrile (AN) by cobalt-mediated radical polymerization (CMRP) is reported for the first time. As a rule, initiation of the polymerization was carried ... [more ▼]

The successful controlled homopolymerization of acrylonitrile (AN) by cobalt-mediated radical polymerization (CMRP) is reported for the first time. As a rule, initiation of the polymerization was carried out starting from a conventional azo-initiator (V-70) in the presence of bis(acetylacetonato)cobalt(II) ([Co(acac)2]) but also by using organocobalt(III) adducts. Molar concentration ratios of the reactants, the temperature, and the solvent were tuned, and the effect of these parameters on the course of the polymerization is discussed in detail. The best level of control was observed when the AN polymerization was initiated by an organocobalt(III) adduct at 0 °C in dimethyl sulfoxide. Under these conditions, poly(acrylonitrile) with a predictable molar mass and molar mass distribution as low as 1.1 was prepared. A combination of kinetic data, X-ray analyses, and DFT calculations were used to rationalize the results and to draw conclusions on the key role played by the solvent molecules in the process. These important mechanistic insights also permit an explanation of the unexpected solvent effect that allows the preparation of well-defined poly(vinyl acetate)-b-poly(acrylonitrile) by CMRP. [less ▲]

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See detailCobalt-mediated radical polymerization of vinyl acetate in miniemulsion: Very fast formation of stable poly(vinyl acetate) latexes at low temperature
Detrembleur, Christophe ULg; Debuigne, Antoine ULg; Bryaskova, Rayna ULg et al

in Macromolecular Rapid Communications (2006), 27(1), 37-41

Poly(vinyl acetate) macroinitiators end-capped by a Co(acac)(2) complex (PVAc-Co(acac)(2)), prepared in bulk by cobalt-mediated radical polymerization (CMRP), are used for the controlled radical ... [more ▼]

Poly(vinyl acetate) macroinitiators end-capped by a Co(acac)(2) complex (PVAc-Co(acac)(2)), prepared in bulk by cobalt-mediated radical polymerization (CMRP), are used for the controlled radical polymerization of vinyl acetate in miniemulsion to give high-molecular-weight polymers and high monomer conversion. Stable poly(vinyl acetate) latexes with solid contents ranging from 25 to 30 wt.-% are prepared within unusually short reaction times (similar to 1 h) at low temperatures (0-30 degrees C). [less ▲]

Detailed reference viewed: 35 (2 ULg)