References of "Sciannaméa, Valérie"
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See detailIn situ nitroxide-mediated polymerization of styrene promoted by the N-tert-butyl-alpha-isopropylnitrone/BPO pair: ESR investigations
Detrembleur, Christophe ULg; Clément, Jean-Louis; Sciannaméa, Valérie et al

in Journal of Polymer Science. Part A, Polymer Chemistry (2013), 51(8), 1786-1795

The styrene polymerization initiated by benzoyl peroxide (BPO) in the presence of N-tert-butyl--isopropylnitrone as nitroxide precursor is well-controlled provided that a prereaction between the nitrone ... [more ▼]

The styrene polymerization initiated by benzoyl peroxide (BPO) in the presence of N-tert-butyl--isopropylnitrone as nitroxide precursor is well-controlled provided that a prereaction between the nitrone and BPO is carried out in suitable conditions prior to polymerization at a higher temperature. Electron spin resonance (ESR) spectroscopy was implemented to probe the nitroxides formed during both steps, that is, the prereaction and polymerization, and to get crucial information regarding the structure of the nitroxides responsible for the polymerization control. ESR studies combined with first principles calculations have evidenced that nitroxides observed during the prereaction in the presence of styrene and during the polymerization steps consist of a mixture of two macronitroxides. One is formed by the addition of a growing polystyrene chain to the nitrone as would be expected. However, the second one results from the addition of a polystyrene chain to tert-butyl nitroso that is in situ formed presumably by decomposition of the first macronitroxide type. [less ▲]

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See detailBiomimetic coatings with robust antibacterial properties
Jérôme, Christine ULg; Cécius, Michaël; Faure, Emilie ULg et al

Conference (2010, July 01)

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See detailA green and refillable antibacterial coating for stainless steel
Faure, Emilie ULg; Charlot, Aurélia; Sciannaméa, Valérie et al

Poster (2010, June 29)

Because of its resistance to corrosion and chemicals, relevant mechanical and esthetical properties, stainless steel (SS) is widely used in the daily life (food industry, household appliances, surgery … ... [more ▼]

Because of its resistance to corrosion and chemicals, relevant mechanical and esthetical properties, stainless steel (SS) is widely used in the daily life (food industry, household appliances, surgery …). However, SS is unable to prevent bacteria from adhering, proliferating and forming a resistant biofilm when ageing. Therefore, surface modification is needed for providing durable antibacterial properties. We report here on an all-in-one approach to prepare refillable antimicrobial films using the layer-by-layer deposition of polyelectrolytes. Specifically designed biocidal multilayered polyelectrolyte films that bear 3,4-dihydroxyphenylalanine (DOPA), known as a promoter of adhesion to inorganic surfaces, were deposited onto SS. DOPA was incorporated in the polycationic chains by radical copolymerisation of N-methacrylated DOPA with the quaternary ammonium salt of 2-(dimethylamino)ethyl methacrylate (DMAEMA+). In order to boost the antibacterial activity of the polycationic layer, AgNO3 was added to the aqueous solution of P(DOPA)-co-P(DMAEMA+), which resulted in the in-situ formation of silver based nanoparticles, sources of biocial Ag+. The layer-by-layer deposition of aqueous P(DOPA)-co-P(DMAEMA+)/AgCl/Ag0 suspension and aqueous solution of poly(styrene sulfonate) provides high antibacterial activity against Gram-negative E. Coli bacteria. Moreover, after silver depletion, films retain some antimicrobial activity, thanks to ammonium groups of the copolymer. We also show that the antibacterial activity of the films can then be easily re-boosted. [less ▲]

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See detailA robust antibacterial coating for stainless steel
Faure, Emilie ULg; Charlot, Aurélia; Sciannaméa, Valérie et al

Conference (2010, March 23)

Because of corrosion, chemical resistance, relevant mechanical and esthetical properties, stainless steel is widely used in the daily life, not only in the building industry but also in the food industry ... [more ▼]

Because of corrosion, chemical resistance, relevant mechanical and esthetical properties, stainless steel is widely used in the daily life, not only in the building industry but also in the food industry, the appliances or in the medical field, including implants in orthopedic surgery. However, stainless steel is unable to prevent bacteria from adhering, proliferating and forming a resistant biofilm. Therefore, surface modification is needed for providing the metal surface with antibacterial properties. The scientific literature is very rich in describing various methods for imparting antibacterial properties to different inorganic supports. However, the activity of the coating is generally time limited by the diffusion of the biocide in the environment. Novel robust and stable antibacterial coatings on stainless steel are thus highly desirable for the durability of the functionality. In this communication, we report on an all-in-one approach to prepare robust antimicrobial films on stainless steel using the layer-by-layer deposition of polyelectrolytes. Novel biocidal multilayered polyelectrolyte films in which the polycationic layer is silver loaded and bears 3,4-dihydroxyphenylalanine (DOPA), known as a promoter of adhesion to inorganic surfaces, were deposited onto stainless steel. DOPA was incorporated in the polycationic chains by radical copolymerisation of N-methacrylated DOPA with the commercially available quaternary ammonium salt of 2-(dimethylamino)ethyl methacrylate (DMAEMA+). Polystyrene sulfonate (PSS) was the polyanionic constituent of the films. In order to boost the antibacterial activity of the polycationic layer, AgNO3 was added to the aqueous solution of P(DOPA)-co-P(DMAEMA+), which resulted in the in-situ formation of silver based nanoparticles (Ag° and AgCl) that are sources of biocial Ag+. The layer-by-layer deposition of aqueous P(DOPA)-co-P(DMAEMA+)/AgCl/Ag0 suspension and aqueous solution of PSS provides stainless steel with high antibacterial activity against Gram-negative E. Coli bacteria. Moreover, after silver depletion, films retain some antimicrobial activity, thanks to the ammonium groups of the copolymer. We will also show how the antibacterial activity of the films can then be easily re-boosted. The multi-functionality of the P(DOPA)-co-P(DMAEMA+) is a key issue in this process (i) the DOPA co-units are anchored to stainless steel, (ii) these co-units reduce partly AgNO3 into Ag0 nanoparticles and stabilize them by chelation, (iii) the chloride counter-anions react with AgNO3 by ionic exchange, leading to the in situ formation of AgCl particles, and (iv) the ammonium groups are responsible for permanent antibacterial activity. Besides the advantage of the all-in-one process, another major advantage of the approach proposed here is the implementation of the whole process of film formation, including the synthesis of P(DOPA)-co-P(DMAEMA+), in aqueous media under very mild conditions. It makes the strategy very attractive for industrial scaling-up and sustainability applications. [less ▲]

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See detailAll-in-one strategy for the fabrication of antimicrobial biomimetic films on stainless steel
Charlot, Aurélia; Sciannamea, Valérie; Lenoir, Sandrine et al

in Journal of Materials Chemistry (2009), 19

Here we report on an all-in-one approach to prepare robust antimicrobial films on stainless steel. The strategy is based on the layer-by-layer deposition of polyelectrolytes. A polycationic copolymer ... [more ▼]

Here we report on an all-in-one approach to prepare robust antimicrobial films on stainless steel. The strategy is based on the layer-by-layer deposition of polyelectrolytes. A polycationic copolymer bearing 3,4-dihydroxyphenylalanine units (DOPA, a major component of natural adhesives) was synthesized and co-deposited with precursors of silver nanoparticles as the first layer. The presence of DOPA units ensures a strong anchoring on the stainless steel substrate, and the silver nanoparticles are sources of biocidal Ag+, providing stainless steel with antimicrobial activity. We show that multilayered films, obtained by alternating this nanoparticle-loaded polycationic copolymer with polystyrene sulfonate, a commercial polyanion, results in stainless steel with high antibacterial activity against Gram-negative E. coli bacteria. The polycationic layers are a reservoir of Ag+ that can be reactivated after depletion. The whole process of film formation, including the synthesis of the copolymer, is conducted in aqueous media under very mild conditions, which makes it very attractive for industrial scale-up and sustainable applications. [less ▲]

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See detailRelevance of a prereaction for the in situ NMP of styrene using the C-phenyl-N-tert-butylnitrone/2,2’-azobis(isobutyronitrile) pair
Sciannamea, Valérie; Catala, Jean-Marie; Jérôme, Robert ULg et al

in Journal of Polymer Science. Part A, Polymer Chemistry (2009), 47(4), 1085-1097

In this article, we compare two routes for carrying out in situ nitroxide-mediated polymerization of styrene using the C-phenyl-N-tert-butylnitrone (PBN)/2,2-azobis(isobutyronitrile) (AIBN) pair to ... [more ▼]

In this article, we compare two routes for carrying out in situ nitroxide-mediated polymerization of styrene using the C-phenyl-N-tert-butylnitrone (PBN)/2,2-azobis(isobutyronitrile) (AIBN) pair to identify the best one for an optimal control. One route consists in adding PBN to the radical polymerization of styrene, while the other approach deals with a prereaction between the nitrone and the free radical initiator prior to the addition of the monomer and the polymerization. The combination of ESR and kinetics studies allowed demonstrating that when the polymerization of styrene is initiated by AIBN in the presence of enough PBN at 110 °C, fast decomposition of AIBN is responsible for the accumulation of dead polymer chains at the early stages of the polymerization, in combination with controlled polystyrene chains. On the other hand, PBN acts as a terminating agent at 70 °C with the formation of a polystyrene end-capped by an alkoxyamine, which is not labile at this temperature but that can be reactivated and chain-extended by increasing the temperature. Finally, the radical polymerization of styrene is better controlled when the nitrone/initiator pair is prereacted at 85 °C for 4 h in toluene before styrene is added and polymerized at 110 °C. [less ▲]

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See detailJoint theoretical experimental investigation of the electron spin resonance spectra of nitroxyl radicals: application to intermediates in in situ nitroxide mediated polymerization (in situ NMP) of vinyl monomers
Zarycz, Natalia; Botek, Edith; Champagne, Benoit et al

in Journal of Physical Chemistry B (2008), 112(34), 10432-10442

Density functional theory (DFT) calculations have been performed to address the structure of nitroxide intermediates in controlled radical polymerization. In a preliminary step, the reliability of ... [more ▼]

Density functional theory (DFT) calculations have been performed to address the structure of nitroxide intermediates in controlled radical polymerization. In a preliminary step, the reliability of different theoretical methods has been substantiated by comparing calculated hyperfine coupling constants (HFCCs) to experimental data for a set of linear and cyclic alkylnitroxyl radicals. Considering this tested approach, the nature of different nitroxides has been predicted or confirmed for (a) the reaction of C-phenyl-N-tert-butylnitrone and AIBN, (b) N-tert-butyl-α-isopropylnitrone and benzoyl peroxide, (c) tert-butyl methacrylate polymerization in the presence of sodium nitrite as mediator, and (d) for the reaction of a nitroso compound with AIBN. Values of HFCC experimentally determined have been confirmed by DFT calculations. [less ▲]

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See detailIn-Situ Nitroxide-Mediated Radical Polymerization (Nmp) Processes: Their Understanding and Optimization
Sciannamea, Valérie; Jérôme, Robert ULg; Detrembleur, Christophe ULg

in Chemical Reviews (2008), 108(3), 1104-26

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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 detailControlled radical polymerization of styrene mediated by the C-phenyl-N-tert-butylnitrone/AIBN pair: Kinetics and electron spin resonance analysis
Sciannamea, Valérie; Catala, Jean-Marie; Jérôme, Robert ULg et al

in Journal of Polymer Science. Part A, Polymer Chemistry (2007), 45(7), 1219-1235

Kinetics of the free radical polymerization of styrene at 110 degrees C has been investigated in the presence of C-phenyl-N-tert-butylnitrone (PBN) and 2,2'-azobis(isobutyronitrile) (AIBN) after ... [more ▼]

Kinetics of the free radical polymerization of styrene at 110 degrees C has been investigated in the presence of C-phenyl-N-tert-butylnitrone (PBN) and 2,2'-azobis(isobutyronitrile) (AIBN) after prereaction in toluene at 85 degrees C. The effect of the prereaction time and the PBN/AIBN molar ratio on the in situ formation of nitroxides and alkoxyamines (at 85 degrees C), and ultimately on the control of the styrene polymerization at 110 degrees C, has been investigated. As a rule, the styrene radical polymerization is controlled, and the mechanism is one of the classical nitroxide-mediated polymerization. Only one type of nitroxide (low-molecular-mass nitroxide) is formed whatever the prereaction conditions at 85 degrees C, and the equilibrium constant (K) between active and dormant species is 8.7 x 10(-10) mol L-1 at 110 degrees C. At this temperature, the dissociation rate constant (k(d)) is 3.7 x 10(-3) s(-1), the recombination rate constant (k(c)) is 4.3 x 10(6) L mol(-1) s(-1), whereas the activation energy (E-a,E-diss), for the dissociation of the alkoxyamine at the chain-end is similar to 125 kJ mol(-1). Importantly, the propagation rate at 110 degrees C, which does not change significantly with the prereaction time and the PBN/AIBN molar ratio at 85 degrees C, is higher than that for the thermal polymerization at 110 degrees C. This propagation rate directly depends on the equilibrium constant K and on the alkoxyamine and nitroxide concentrations, as well. [less ▲]

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See detailFast controlled radical polymerization of styrene mediated by oligomeric nitroxides formed in situ
Sciannamea, Valérie; Catala, Jean-Marie; Jérôme, Robert ULg et al

in Macromolecular Rapid Communications (2007), 28(2), 147-151

In the presence of an oligomeric hindered secondary amine added with peracetic acid as the oxidant, radical polymerization of styrene is fast and controlled at 110 degrees C. Under these experimental ... [more ▼]

In the presence of an oligomeric hindered secondary amine added with peracetic acid as the oxidant, radical polymerization of styrene is fast and controlled at 110 degrees C. Under these experimental conditions, an oligomeric nitroxide is formed in situ. This polymerization is 2.5 faster than polymerization mediated by the alkoxyamine derivated from TIPNO (2,2,5-trimethyl-4- phenyl-3-azahexane-3-nitroxide), which generates a low molar mass nitroxide. Similarly, substitution of a low molar mass secondary amine, 2,2,6, 6-tetramethylpiperidone (4-oxo-TMP), for the oligomeric secondary amine maintains the control on the polymerization, which is however 4.6 times slower, all the other conditions being the same. The in situ formation of the oligomeric nitroxide has been confirmed by electron spin resonance (ESR). [less ▲]

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See detailKinetics and electron spin resonance study of the radical polymerization of n-butyl acrylate mediated by a nitroxide precursor: C-phenyl-N-tert-butylnitrone
Sciannamea, Valérie; Bernard, Maxime; Catala, Jean-Marie et al

in Journal of Polymer Science. Part A, Polymer Chemistry (2006), 44(21), 6299-6311

The C-phenyl-N-tert-butylnitrone/azobisisobutyronitrile pair is able to impart control to the radical polymerization of n-butyl acrylate as long as a two-step process is implemented, that is, the ... [more ▼]

The C-phenyl-N-tert-butylnitrone/azobisisobutyronitrile pair is able to impart control to the radical polymerization of n-butyl acrylate as long as a two-step process is implemented, that is, the prereaction of the nitrone and the initiator in toluene at 85 degrees C for 4 h followed by the addition and polymerization of n-butyl acrylate at 110 degrees C. The structure of the in situ formed nitroxide has been established from kinetic and electron spin resonance data. The key parameters (the dissociation rate constant, combination rate constant, and equilibrium constant) that govern the process have been evaluated. The equilibrium constant between the dormant and active species is close to 1.6 x 10(-12) mol L-1 at 110 degrees C. The dissociation rate constant and the activation energy for the C-ON bond homolysis are 1.9 x 10(-3) s(-1) and 122 +/- 15 kJ mol(-1), respectively. The rate constant of recombination between the propagating adical and the nitroxide is as high as 1.2 x 10(9) L mol(-1) s(-1). Finally, well-defined poly(n-butyl acrylate)-b-polystyrene block copolymers have been successfully prepared. [less ▲]

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See detailSupported cobalt mediated radical polymerization (SCMRP) of vinyl acetate and recycling of the cobalt complex
Sciannamea, Valérie; Debuigne, Antoine ULg; Piette, Yasmine ULg et al

in Chemical Communications (2006), (40), 4180-4182

Cobalt complexes supported on silica and Merrifield resin are effective mediators for the controlled radical polymerization of vinyl acetate.

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See detailThe key role of nitrones in the controlled radical polymerization of vinyl monomers
Sciannamea, Valérie

Doctoral thesis (2005)

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See detailAbility of nitrones of various structures to control the radical polymerization of styrene mediated by in situ formed nitroxides
Sciannamea, Valérie; Guerrero-Sanchez, Carlos; Schubert, Ulrich S. et al

in Polymer (2005), 46(23), 9632-9641

The ability of several nitrones to control the radical polymerization of styrene at 110 °C has been investigated by high-throughput experimentation. The nitrone/free radical initiator pair dictates the ... [more ▼]

The ability of several nitrones to control the radical polymerization of styrene at 110 °C has been investigated by high-throughput experimentation. The nitrone/free radical initiator pair dictates the structure of the nitroxide and the alkoxyamine formed in situ, which determines the position of the equilibrium between the active and the dormant species operating in the nitroxide-mediated polymerization. For the styrene polymerization to be controlled, the nitrone must be reacted with 2,2'-azo-bis-isobutyronitrile (AIBN) at 85 °C, prior to addition of styrene and polymerization at 110 °C. The effect of the nitrone structure on the kinetics of the styrene polymerization has been emphasized. Amongst all the nitrones tested, those of the C-phenyl-N-tert-butylnitrone (PBN) type are the most efficient in terms of polymerization rate, control of molecular weight and polydispersity. Electrophilic substitution of the phenyl group of PBN by either an electrodonor or an electroacceptor group has only a minor effect on the polymerization kinetics. Importantly, the polymerization rate is not governed by the thermal polymerization of styrene but by the alkoxyamine formed in situ during the pre-reaction step. The initiation efficiency is, however, very low, consistent with a limited conversion of the nitrone into nitroxide and alkoxyamine. [less ▲]

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See detailESR studies of the in-situ nitroxide-mediated polymerization (NMP) of styrene using a nitrone
Sciannamea, Valérie; Bernard, M.; Catala, J.-M. et al

Conference (2004, November 26)

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See detailSynthesis of copolymer brushes endowed with adhesion to stainless steel surfaces and antibacterial properties by controlled nitroxide-mediated radical polymerization
Ignatova, Miléna; Voccia, Samuel; Gilbert, Bernard ULg et al

in Langmuir (2004), 20(24), 10718-10726

Novel copolymer brushes have been synthesized by a two-step "grafting from" method that consists of the electrografting of poly(2-phenyl-2-(2,2,6,6-tetramethyl-piperidin-1-yloxy)-ethylacrylate) onto ... [more ▼]

Novel copolymer brushes have been synthesized by a two-step "grafting from" method that consists of the electrografting of poly(2-phenyl-2-(2,2,6,6-tetramethyl-piperidin-1-yloxy)-ethylacrylate) onto stainless steel, followed by the nitroxide-mediated radical polymerization of 2-(dimethylamino ethyl)acrylate and styrene or n-butyl acrylate, initiated from the electrografted polyacrylate chains. The grafted copolymers were quaternized in order to endow them with antibacterial properties. Peeling tests have confirmed the strong adhesion of the grafted copolymer onto the stainless steel substrate. Quartz crystal microbalance experiments have proven that fibrinogen adhesion is lower on the hydrophilic quaternized films compared to the nonionic counterpart. Such quaternized copolymers exhibit significant antibacterial activity against the Gram-positive bacteria S. aureus and the Gram-negative bacteria E. coli. [less ▲]

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