References of "Grignard, Bruno"
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See detailSynthesis of microsphere-loaded porous polymers by combining emulsion and dispersion polymerisations in supercritical carbon dioxide
Boyère, Cédric ULg; Léonard, Alexandre ULg; Grignard, Bruno ULg et al

in Chemical Communications (2012), 48(67), 8356-8358

Highly porous materials were produced by acrylamide polymerisation templated by supercritical CO2-in-water emulsions using new fluorinated glycosurfactants. Properties of the resulting polymer scaffolds ... [more ▼]

Highly porous materials were produced by acrylamide polymerisation templated by supercritical CO2-in-water emulsions using new fluorinated glycosurfactants. Properties of the resulting polymer scaffolds were tuned by performing dispersion polymerisations within their cavities filled with supercritical CO2. [less ▲]

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See detailOnline monitoring of heterogeneous polymerizations in supercritical carbon dioxide by Raman spectroscopy
Grignard, Bruno ULg; Gilbert, Bernard ULg; Malherbe, Cédric ULg et al

in Chemphyschem : A European Journal of Chemical Physics and Physical Chemistry (2012), 13(11), 2666-2670

A novel setup is described to monitor the kinetics of homogeneous and heterogeneous reactions online using Raman spectroscopy under high pressure. The arrangement is based on a high-pressure reactor ... [more ▼]

A novel setup is described to monitor the kinetics of homogeneous and heterogeneous reactions online using Raman spectroscopy under high pressure. The arrangement is based on a high-pressure reactor equipped with a sapphire window in combination with a mobile probe that allows the collection of the back-scattered Raman signal at 360°. [less ▲]

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See detailMetal-free strategies for the synthesis of functional and well-defined polyphosphoesters
Clement, Benoît ULg; Grignard, Bruno ULg; Koole, Leo et al

in Macromolecules (2012), 45(11), 4476-4486

We report here metal-free strategies using organocatalysis based on supramolecular recognition for the ring-opening polymerization (ROP) of several cyclic phosphate monomers (CPMs) by a variety of ... [more ▼]

We report here metal-free strategies using organocatalysis based on supramolecular recognition for the ring-opening polymerization (ROP) of several cyclic phosphate monomers (CPMs) by a variety of organocatalysts such as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5,7-triazabicyclo[4.4.0]undec-5-ene (TBD), and a bicomponent thiourea−tertiary amine catalyst. Each of these catalysts is efficient to produce linear polyphosphoesters (PPEs) from CPMs but with different sensitivity toward transesterification side reactions. The strong basicity of DBU is sufficient to activate an alcohol initiating the polymerization in the absence of any other cocatalyst. Nevertheless, side chain transfer reactions leading to branched and/or cyclic polymeric structures are observed, especially for high monomer conversion. Unlike DBU, TBD is a dual catalyst activating both the alcohol and the monomer. This dual activation allows shorter polymerization time, but SEC analyses of polyphosphates reveal bimodal molecular weight distribution due to chains coupling. Finally, a mixture of DBU and thiourea (TU) appears by far the most efficient catalyst to carry out fast and controlled polymerization while minimizing transesterification reactions, even at near-complete conversion. Compared with polymerizations carried out with Sn(Oct)2 as a metal catalyst, the control of polymerization is much better so that it is possible to prepare polyphosphoesters (PPEs) with molecular weight close to 70 000 g mol−1 and polydispersity index below 1.10. Simultaneous activation by TU of both CPMs and the alcohol group of the initiator by DBU proves to be an effective and robust ROP catalytic system to synthesize polymers with predictable molecular weight and narrow polydispersity. The chain extension experiments through the use of hydroxy end- capped PPEs as macroinitiators confirm the controlled/living nature of the DBU/TU-catalyzed ROP of CPMs and pave the way to the synthesis of block copolymers based on polyphosphates. [less ▲]

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See detailSynthesis of new biomimetic biodegradable materials for clinical use
Clement, Benoît ULg; Grignard, Bruno ULg; Lecomte, Philippe ULg et al

Poster (2012, May 10)

For recent decades, the most commonly biodegradable polymers used in clinical and therapeutic applications are aliphatic polyesters such as polyglycolide, polylactide, polycaprolactone and their ... [more ▼]

For recent decades, the most commonly biodegradable polymers used in clinical and therapeutic applications are aliphatic polyesters such as polyglycolide, polylactide, polycaprolactone and their copolymers, mainly due to their excellent biocompatibility and biodegradability properties. However, the lack of functional groups on the backbone of polyesters, which could otherwise be used for tuning physicochemical properties and for introducing bioactive units, limits their further biomedical applications. Polymers with repeating phosphoester bonds in the backbone are structurally versatile and biodegradable through hydrolysis and possibly enzymatic digestion of phosphates linkages under physiological conditions. An advantage of polyphosphoesters (PPEs) compared to aliphatic polyesters is the possible functionalization of side chains due to the patenvalency of the phosphorous atom, allowing the introduction of bioactive molecules and extensive modification of the physical and chemical properties of final material. The Ring-Opening Polymerization (ROP) of cyclic esters is a well-established process to provide linear polyesters with predictable molecular weight, narrow polydispersity and well-defined end-groups. Up to now, metallic compounds are particularly used as initiators or polymerization catalysts to synthetize these materials but metallic derivatives are cytotoxic and a lack of residual metal contaminants is strongly required in view of biomedical applications. To tackle these drawbacks, we developed synthetic approaches that are metal-free (i.e., organocatalytic) using organocatalysis based on supramolecular recognition. A variety of organocatalysts such as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5,7-triazabicyclo[4.4.0]undec-5-ene (TBD) and a bicomponent thiourea-tertiary amine catalyst were studied. Each of these catalysts is efficient to produce linear polyphosphoesters (PPEs) from cyclic phosphate monomers (CPMs) but with different sensitivity towards transesterification side reactions. Compared with polymerizations carried out with Sn(Oct)2 as a metal catalyst, the control of polymerization is much better so that it is possible to prepare PPEs with molecular weight close to 70000 g.mol-1 and polydispersity index below 1.10. The chain extension experiments through the use of hydroxy end-capped PPEs as macro-initiators confirm the controlled/living nature of organo-catalyzed ROP of CPMs and pave the way to the synthesis of block copolymers based on polyphosphates. Finally, these polymerizations procedures are expected to facilitate the synthesis of well-defined PPEs with various architectures and free of potentially toxic metal remnants. The easy availability of catalysts, the mild conditions of polymerizations and the metal-free nature of the polymerizations makes these catalysts very attractive candidates for the synthesis of PPEs for biomedical applications such as drug and gene delivery, tissue engineering and dental applications. [less ▲]

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See detailNew fluorinated surfactant for nanogels preparation in supercritical CO2
Alaimo, David ULg; Beigbeder, Alexandre; Dubois, Philippe et al

Poster (2011, April 29)

Detailed reference viewed: 32 (5 ULg)
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See detailElectrospinning of a functional perfluorinated block copolymer as a powerful route for imparting superhydrophobicity and corrosion resistance to aluminum substrates
Grignard, Bruno ULg; Vaillant, Alexandre; de Coninck, Joel et al

in Langmuir (2011), 27(1), 335-342

Superhydrophobic aluminum surfaces with excellent corrosion resistance were successfully prepared by electrospinning of a novel fluorinated diblock copolymer solution. Micro- and nanostructuration of the ... [more ▼]

Superhydrophobic aluminum surfaces with excellent corrosion resistance were successfully prepared by electrospinning of a novel fluorinated diblock copolymer solution. Micro- and nanostructuration of the diblock copolymer coating was obtained by electrospinning which proved to be an easy and cheap electrospinning technology to fabricate superhydrophobic coating. The diblock copolymer is made of poly(heptadecafluorodecylacrylate-co-acrylic acid) (PFDA-co-AA) random copolymer as the first block and polyacrylonitrile (PAN) as the second one. The fluorinated block promotes hydrophobicity to the surface by reducing the surface tension, while its carboxylic acid functions anchor the polymer film onto the aluminum surface after annealing at 130 °C. The PAN block of this copolymer insures the stability of the structuration of the surface during annealing, thanks to the infusible character of PAN. It is also demonstrated that the so-formed superhydrophobic coating shows good adhesion to aluminum surfaces, resulting in excellent corrosion resistance. [less ▲]

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See detailCorrelation between superhydrophobicity and the power spectral density of randomly rough surfaces
Awada, Houssein; Grignard, Bruno ULg; Jérôme, Christine ULg et al

in Langmuir (2010), 26(23), 17798-17803

We show experimentally and analytically that for single-valued, isotropic, homogeneous, randomly rough surfaces consisting of bumps randomly protruding over a continuous background, superhydrophobicity is ... [more ▼]

We show experimentally and analytically that for single-valued, isotropic, homogeneous, randomly rough surfaces consisting of bumps randomly protruding over a continuous background, superhydrophobicity is related to the power spectral density of the surface height, which can be derived from microscopy measurements. More precisely, superhydrophobicity correlates with the third moment of the power spectral density, which is directly related to the notion of Wenzel roughness (i.e., the ratio between the real area of the surface and its projected area). In addition, we explain why randomly rough surfaces with identical root-mean-square roughness values may behave differently with respect to water repellence and why roughness components with wavelength larger than 10 μm are not likely to be of importance or, stated otherwise, why superhydrophobicity often requires a contribution from submicrometer-scale components such as nanoparticles. The analysis developed here also shows that the simple thermodynamic arguments relating superhydrophobicity to an increase in the sample area are valid for this type of surface, and we hope that it will help researchers to fabricate efficient superhydrophobic surfaces based on the rational design of their power spectral density. [less ▲]

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See detailNew fluorinated surfactants for nanogels preparation in supercritical CO2
Alaimo, David ULg; Beigbeder, Alexandre; Dubois, Philippe et al

Poster (2010, November 29)

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See detailContribution of "click chemistry" to the macromolecular engineering of aliphatic polyesters
Riva, Raphaël ULg; Schmeits, Stephanie ULg; Croisier, Florence ULg et al

Poster (2010, July 13)

In this work, click chemistry was sucessfully applied to the chemical modification of aliphatic polyesters with the purpose to tailor their physical properties. The developped strategy was then applied to ... [more ▼]

In this work, click chemistry was sucessfully applied to the chemical modification of aliphatic polyesters with the purpose to tailor their physical properties. The developped strategy was then applied to the synthesis of materials, such as smart partially degradable hydrogels or antibacterial polyesters. Last, the synthesis of amphiphilic star-shaped copolyester was investigated. [less ▲]

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See detail“One-pot” dispersion ATRP and alkyne-azide Huisgen’s 1,3-dipolar cycloaddition in supercritical carbon dioxide: towards the formation of functional microspheres
Grignard, Bruno ULg; Calberg, Cédric ULg; Jérôme, Christine ULg et al

in Journal of Supercritical Fluids (2010), 53(1-3), 151-155

Functional polymers were successfully prepared in scCO2 by combining alkyne-azide 1,3-dipolar Huisgen’s cycloaddition and dispersion ATRP in a “one pot” process using new perfluorinated polymeric amino ... [more ▼]

Functional polymers were successfully prepared in scCO2 by combining alkyne-azide 1,3-dipolar Huisgen’s cycloaddition and dispersion ATRP in a “one pot” process using new perfluorinated polymeric amino-based ligands that had a dual role, i.e. the complexation of the copper catalyst and the stabilization of growing particles. [less ▲]

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See detailDispersion nitroxide mediated polymerization of methyl methacrylate in supercritical carbon dioxide using in situ formed stabilizers
Grignard, Bruno ULg; Phan, Tran; Bertin, Denis et al

in Polymer Chemistry (2010), 1(6), 837-840

PMMA microspheres were successfully prepared in supercritical carbon dioxide by controlled dispersion nitroxide mediated polymerization of methyl methacrylate using perfluorinated stabilizers that were ... [more ▼]

PMMA microspheres were successfully prepared in supercritical carbon dioxide by controlled dispersion nitroxide mediated polymerization of methyl methacrylate using perfluorinated stabilizers that were generated “in situ”. [less ▲]

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See detailSuperhydrophobic aluminum surfaces by deposition of micelles of fluorinated block copolymers
Desbief, Simon; Grignard, Bruno ULg; Detrembleur, Christophe ULg et al

in Langmuir (2010), 26(3), 2057-2067

Superhydrophobic surfaces are generated by chemisorption on aluminum substrates of fluorinated block copolymers synthesized by reversible addition−fragmentation chain transfer in supercritical carbon ... [more ▼]

Superhydrophobic surfaces are generated by chemisorption on aluminum substrates of fluorinated block copolymers synthesized by reversible addition−fragmentation chain transfer in supercritical carbon dioxide. In an appropriate solvent, those block copolymers can form micelles with a fluorinated corona, which are grafted on the aluminum substrate thanks to the presence of carboxylic acid groups in the corona. Water contact angle and drop impact analysis were used to characterize the wettability of the films at the macroscale, and atomic force microscopy measurements provided morphological information at the micro- and nanoscale. The simple solvent casting of the polymer solution on a hydroxylated aluminum surface results in a coating with multiscale roughness, which is fully superhydrophobic over areas up to 4 cm2. [less ▲]

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See detailSuperhydrophobic surfaces by electrospinning of polymer mixtures
Grignard, Bruno ULg; Vaillant, Alexandre; De Coninck, Joel et al

Poster (2009, December 14)

Detailed reference viewed: 37 (6 ULg)
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See detailFirst example of “click” copper(I) catalyzed azide-alkyne cycloaddition in supercritical carbon dioxide: Application to the functionalization of aliphatic polyesters
Grignard, Bruno ULg; Schmeits, Stephanie ULg; Riva, Raphaël ULg et al

in Green Chemistry (2009), 11

The modification of aliphatic polyesters by the copper(I) catalyzed azide-alkyne cycloaddition (CuAAC) was successfully implemented in supercritical carbon dioxide (scCO2). Due to the remarkable ... [more ▼]

The modification of aliphatic polyesters by the copper(I) catalyzed azide-alkyne cycloaddition (CuAAC) was successfully implemented in supercritical carbon dioxide (scCO2). Due to the remarkable properties of scCO2, the CuAAC reaction turned out to be quantitative even though the aliphatic polyesters used in this work were insoluble in scCO2. Interestingly enough, the conditions were mild enough to prevent polymer degradation from occurring and finally, efficient removal of the catalyst (>96%) was achieved by scCO2 extraction. [less ▲]

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See detailNew perfulorinated macroligand for the implementation of dispersion atom transfer radical polymerization in sc CO2
Grignard, Bruno ULg; Calberg, Cédric ULg; Jérôme, Christine ULg et al

Poster (2009, September 17)

Due to an increasing need for polymers with well-defined architecture (diblock-, graft-, star-shaped copolymers), molecular weight and/or functional end-groups, the use of controlled radical ... [more ▼]

Due to an increasing need for polymers with well-defined architecture (diblock-, graft-, star-shaped copolymers), molecular weight and/or functional end-groups, the use of controlled radical polymerization (CRP) in scCO2 has started to gain attention. Among all the controlled processes, Atom Transfer Radical Polymerization has emerged as a robust tool for the preparation of polymers with well-defined molecular weight, architecture and chain-end functionality. In a very recent paper, we reported the first efficient dispersion ATRP of methyl methacrylate (MMA) in scCO2 using a fluorinated polymeric ligand that had a dual role, i.e., the complexation of the copper salt and the stabilization of PMMA growing particles. In this contribution, we extended this new system to the dispersion ATRP of styrene2, to the synthesis of diblock copolymers beads2 or to the preparation of PMMA particles by AGET ATRP. Because both ATRP and alkyne-azide Huisgen’s 1,3-dipolar cycloaddition relies on the use of a Cu(I) catalyst, synthesis of pyrene end-functionalized polymers by simultaneous dispersion ATRP and click reaction was also investigated in supercritical carbon dioxide. Finally, the immobilization of these new macroligands onto an inorganic support leads to the formation of pseudo-homogeneous catalyst that were successfully used to prepare CO2-soluble perfluorinated methacrylate and depending on the molecular weight and TEDETA composition of the macroligand, results obtained by supported ATRP without addition of Cu(II) as deactivator are identical to those obtained by homogeneous ATRP. [less ▲]

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See detailIn situ formation of stabilizers for the implementation of dispersion nitroxide mediated polymerization of MMA in supercritical carbon dioxide
Grignard, Bruno ULg; Gigmes, Didier; Jérôme, Christine ULg et al

Poster (2009, September 17)

Controlled dispersion Nitroxide Mediated Polymerization (NMP) of methyl methacrylate (MMA) was successfully carried out for the first time in supercritical carbon dioxide (scCO2) in the presence of CO2 ... [more ▼]

Controlled dispersion Nitroxide Mediated Polymerization (NMP) of methyl methacrylate (MMA) was successfully carried out for the first time in supercritical carbon dioxide (scCO2) in the presence of CO2-philic perfluorinated surfactant that was generated “in situ”. The control of the MMA polymerization relies on the strategy developed by Charleux et al. that consists of using a SG1-based alkoxyamine, i.e. the block-builder, in the presence of small amount of styrene. In a first step, CO2 soluble polyheptadecafluorodecylacrylate was prepared in scCO2 using block-builder as an alkoxyamine. In a second step, nitroxide SG1 mediated dispersion polymerization of MMA was conducted at 70°C and 300 bar in the presence of 5 w% of SG1 terminated surfactant compared to the monomer. Different monomer to alkoxyamine molar ratios were investigated in order to target different molecular weights. In each case, the monomer conversion was high (>90 %), the experimental molecular weight was in good agreement with the theoretical value and the polydispersity was narrow (Mw/Mn ~1.2). Moreover, after depressurisation of the cell, PMMA was collected as a free flowing powder consisting of small sized microspheres. [less ▲]

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See detailNew developments in the functionalization of aliphatic polyesters by "click" copper-catalyzed azide-alkyne cycloaddition
Lecomte, Philippe ULg; Riva, Raphaël ULg; Schmeits, Stephanie ULg et al

Conference (2009, June 03)

Nowadays, biodegradable and biocompatible aliphatic polyesters are widely used as environmentally friendly thermoplastics and biomaterials. Nevertheless, the absence of any pendant functional group is a ... [more ▼]

Nowadays, biodegradable and biocompatible aliphatic polyesters are widely used as environmentally friendly thermoplastics and biomaterials. Nevertheless, the absence of any pendant functional group is a severe limitation for the development of novel applications. Our strategy aiming at functionalizing aliphatic polyesters relies on the “click” copper-catalyzed cycloaddition (CuAAC) of alkynes duly substituted by functional groups or even chains onto PCL bearing pendant azides. The aliphatic polyesters bearing pendant azides have been very efficiently synthesized by a straightforward approach, which relies on the ring-opening copolymerization of αClεCL (or γBrεCL) and εCL (or lactide) followed by reaction with sodium azide to convert pendant chlorides or bromides into azides. The alternative reported by Emrick et al. is based on the CuAAC reaction of azides substituted by any functional group onto copolyesters of poly(ε-caprolactone) bearing pendant alkynes. Interestingly enough, Emrick et al. carried out the CuAAc reaction in water at 80°C. Unfortunately, it turned out, at least in our hands, that these conditions can not be extended to the derivatization of more sensitive aliphatic polyesters because degradation was then unavoidable. Nevertheless, we found out that degradation can be minimized whenever the CuAAC reaction is carried out in an organic solvent at lower temperature. Typically, the CuAAC reaction was carried out in DMF or THF at 35°C. Recently, it was shown that supercritical carbon dioxide can be used as a more environmentally friendly solvent than DMF or THF. The contamination by catalytic residues of aliphatic polyesters functionalized by the CuAAC reaction is a severe limitation in view of future applications, especially in the biomedical field. In the last part of this talk, a special attention will be paid on our current efforts to get rid of copper residues. [less ▲]

Detailed reference viewed: 64 (22 ULg)