References of "Grignard, Bruno"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailCobalt-mediated radical polymerization of vinyl acetate and acrylonitrile in supercritical carbon dioxide
Kermagoret; Chau, Ngoc Do Quyen; Grignard, Bruno ULg et al

in Macromolecular Rapid Communications (2016), 39(6), 539-544

Cobalt-mediated radical polymerization (CMRP) of vinyl acetate (VAc) is successfully achieved in supercritical carbon dioxide (scCO 2 ). CMRP of VAc is conducted using an alkyl-cobalt(III) adduct that is ... [more ▼]

Cobalt-mediated radical polymerization (CMRP) of vinyl acetate (VAc) is successfully achieved in supercritical carbon dioxide (scCO 2 ). CMRP of VAc is conducted using an alkyl-cobalt(III) adduct that is soluble in scCO2 . Kinetics studies coupled to visual observations of the polymerization medium highlight that the melt viscosity and PVAc molar mass ( Mn ) are key parameters that affect the CMRP in scCO2. It is noticed that CMRP is controlled for M n up to 10 000 g mol−1 , but loss of control is progressively observed for higher molar masses when PVAc precipitates in the polymerization medium. Low molar mass PVAc macroinitiator, prepared by CMRP in scCO2 , is then successfully used to initiate the acrylonitrile polymerization. PVAc-b-PAN block copolymer is collected as a free flowing powder at the end of the process although the dispersity of the copolymer increases with the reaction time. Although optimization is required to decrease the dispersity of the polymer formed, this CMRP process opens new perspectives for macromolecular engineering in scCO2 without the utilization of fluorinated comonomers or organic solvents. [less ▲]

Detailed reference viewed: 96 (14 ULg)
Full Text
Peer Reviewed
See detailRing opening polymerization of ε-caprolactone in the presence of wet β-cyclodextrin: effect of the operative pressure and of water molecules in the β-cyclodextrin cavity
Galia, Alessandro; Scialdone, Onofrio; Spanò, Tiziana et al

in RSC Advances (2016), 6

The ring opening polymerization (ROP) of ε-caprolactone (CL) in the presence of β-cyclodextrin (β−CD) was performed in batch reactors both at room pressure and with the reaction system pressurized with ... [more ▼]

The ring opening polymerization (ROP) of ε-caprolactone (CL) in the presence of β-cyclodextrin (β−CD) was performed in batch reactors both at room pressure and with the reaction system pressurized with CO2, N2 or Ar. Significant enhancements of the polymerization rate was observed when the ROP was carried out with wet β−CD under pressure. For example, after 24 hours at 120°C with β−CD/CL molar ratio of about 1/100, the monomer conversion increased from β 4 to 98-99% when the pressure was changed from 0.1 to 12.5-13.0 MPa independently on the nature of the compressing gas. MALDI-TOF analyses indicated that a major fraction of polymer chains obtained in pressurized systems was initiated by water molecules. Collected results suggest that at 12-13 MPa wet β−CD can catalyse both the ring opening of ε-caprolactone and the polymerization of the obtained linear specie and that high energy water molecules located inside the cavity of the cyclic oligosaccharide must play a role in initiating the polymerization. The trend of number average molecular weight and the results of MALDI-TOF analyses obtained in polymerizations performed for long reaction times and in hydrolysis test of commercial poly(ε-caprolactone) indicate that wet β−CD can work as an artificial lipase enzyme under adopted conditions. [less ▲]

Detailed reference viewed: 23 (6 ULg)
Full Text
Peer Reviewed
See detailA comprehensive density functional theory study of the key role of fluorination and dual hydrogen bonding in the activation of the epoxide/CO2 coupling by fluorinated alcohols
Alves, Margot ULg; Méreau, Raphaël; Grignard, Bruno ULg et al

in RSC Advances (2016), 6(43), 36327-36335

The activation mechanism of the CO2/propylene oxide coupling catalysed by a bicomponent organocatalyst combining the use of TBABr with (multi)phenolic or fluorinated hydrogen bond donors (HBDs) was ... [more ▼]

The activation mechanism of the CO2/propylene oxide coupling catalysed by a bicomponent organocatalyst combining the use of TBABr with (multi)phenolic or fluorinated hydrogen bond donors (HBDs) was investigated using the Density Functional Theory (DFT). Thus, it was shown that increasing the number of electron withdrawing trifluoromethyl substituents in HBDs strengthens their proton donor capability and allows a better stabilization by hydrogen bonding of the intermediates and transition states. In addition, the high efficiency of fluorinated monoalcohol activators is related to a dual hydrogen bonding mechanism by two fluorinated molecules that cooperatively contribute to the CO2/propylene oxide coupling. [less ▲]

Detailed reference viewed: 38 (10 ULg)
See detailOrganocatalytic coupling of carbon dioxide with epoxides: the unexpected booster effect of fluoroalcohols
Grignard, Bruno ULg; Gennen, Sandro ULg; Alves, Margot ULg et al

Poster (2015, December 19)

Valorising CO2 as a C1 feedstock for producing added value building blocks is seducing as it is a free and in exhaustive waste resulting from human activity. Carbon dioxide is a thermodynamically and ... [more ▼]

Valorising CO2 as a C1 feedstock for producing added value building blocks is seducing as it is a free and in exhaustive waste resulting from human activity. Carbon dioxide is a thermodynamically and kinetically stable molecule that can be converted into cyclic carbonates by coupling with epoxides. Cyclic carbonates are valuable products that find applications as solvents, electrolytes or as monomers for polyurethanes synthesis. Although the CO2/epoxide coupling reaction has been extensively studied, the development of organocatalysts that are highly efficient under mild experimental conditions still remains a challenge. Onium salts are the most common catalysts that show reasonable catalytic activity at high pressure (> 100 bars) and high temperature (> 100°C) only. Fortunately, the efficiency of these organocatalysts can be improved by addition of appropriate hydrogen bond donors activators (HBD). In this talk, we will report the development of a new highly efficient catalytic platform consisting in an onium halide salt combined with HBD activators for the fast and solvent-free synthesis of cyclic carbonates by coupling CO2 with epoxides. The cocatalytic effect of series of HBDs will be demonstrated by detailed online kinetics studies under pressure using Raman or IR spectroscopy. We will show that our new organocatalytic platform facilitates the fast conversion of epoxy groups into cyclic carbonates under mild experimental conditions, and can be easily implemented to the modification of epoxidized vegetable oils. The synergistic effects between HBDs and onium salt will be highlighted by a detailed mechanistic study of the reaction through DFT calculations. [less ▲]

Detailed reference viewed: 37 (3 ULg)
See detailNew efficient organocatalytic system for solvent-free chemical fixation of CO2 into epoxides
Panchireddy, Satyannarayana ULg; Gennen, Sandro ULg; Alves, Margot ULg et al

Poster (2015, September 11)

Due to concerns about global warming combined with the decrease of fossil resources, the chemical transformation of carbon dioxide (CO2) into added-value products has gained interest in both academic and ... [more ▼]

Due to concerns about global warming combined with the decrease of fossil resources, the chemical transformation of carbon dioxide (CO2) into added-value products has gained interest in both academic and industrial fields. To date, the chemical fixation of CO2 onto epoxides with the formation of cyclic carbonates (CC) is one of the most promising ways to valorise CO2 at an industrial scale. Indeed, CC are useful monomers for polycarbonate synthesis and they can react with primary amines to produce 2-hydroxyethylurethane. This reaction can be extrapolated to the synthesis of non-isocyanate polyurethanes (NIPUs) by a step growth polymerization between bifunctional CC and diamines. [less ▲]

Detailed reference viewed: 123 (12 ULg)
Full Text
Peer Reviewed
See detailOrganocatalytic promoted coupling of carbon dioxide with epoxides: a rational investigation of the cocatalytic activity of various hydrogen bond donors
Alves, Margot ULg; Grignard, Bruno ULg; Gennen, Sandro ULg et al

in Catalysis Science & Technology (2015), 5(9), 4636-4643

A catalytic platform based on an onium salt used in combination with organic cocatalysts of various structures was developed for the efficient CO2/epoxide coupling under mild conditions. Through detailed ... [more ▼]

A catalytic platform based on an onium salt used in combination with organic cocatalysts of various structures was developed for the efficient CO2/epoxide coupling under mild conditions. Through detailed kinetic studies by in-situ FT-IR spectroscopy, a rational investigation of the efficiency of a series of commercially available hydrogen bond donors co-catalysts was realized and the influence of different parameters such as the pressure, the temperature, the catalyst loading, and the nature of the epoxide on the reaction kinetics was evaluated. Fluorinated alcohols were found to be more efficient than other hydrogen bond donor activators proposed previously in the literature under similar conditions. [less ▲]

Detailed reference viewed: 84 (25 ULg)
See detailCO2-sourced non-isocyanate polyurethanes: from the monomer synthesis to the elaboration of polymeric materials
Gennen, Sandro ULg; Grignard, Bruno ULg; Gilbert, Bernard ULg et al

Conference (2015, July 07)

Due to problems related to the rarefaction of fossil resources and the global warming that comes from CO2 emissions, new carbon feedstocks that are abundant, renewable, non-toxic, inexpensive and ... [more ▼]

Due to problems related to the rarefaction of fossil resources and the global warming that comes from CO2 emissions, new carbon feedstocks that are abundant, renewable, non-toxic, inexpensive and environmentally friendly must be explored to produce chemicals. Besides the valorization of bio-based raw materials, the use of CO2 as a C1 carbon source into added-value products has gained interest in both academic and industrial fields. One promising way to valorize CO2 relies on its chemical fixation onto epoxides to produce cyclic carbonates that find applications as electrolytes in lithium ion batteries, as aprotic polar solvents or as useful intermediates for polycarbonates. Cyclic carbonates also react with primary amines to produce 2-hydroxyethylurethane. This reaction can be extrapolated to the synthesis of non-isocyanate polyurethanes (NIPU) by polyaddition of bifunctional cyclic carbonates with diamines.5 This study focusses on (i) the synthesis of cyclic carbonates using new highly efficient organocatalysts and (ii) their valorization as monomers to produce non-isocyanate polyurethanes. First, we have identified a bicomponent organocatalyst for the very fast synthesis of cyclic carbonates from CO2 and epoxides under very mild reaction conditions. Kinetics of reactions were followed by online Raman spectroscopy. NMR titrations were realized to evidence the mechanism of activation of this novel organocatalytic system that will be discussed in detail this talk. The second objective relies on the development of new efficient organocatalysts for the synthesis of high molar masses NIPUs in short reaction times. Organic compounds interacting with the cyclic carbonate by hydrogen bonding were identified and their catalytic activity was highlighted by a model reaction between ethylene carbonate and a primary amine before extrapolation to the synthesis of NIPUs that find applications as coatings or foamed materials. [less ▲]

Detailed reference viewed: 154 (10 ULg)
See detailEfficient hydrogen-bond donor activators for the synthesis of bio-based cyclic carbonates from CO2 and vegetable oils: a combined in-situ FT-IR and DFT study
Alves, Margot ULg; Méreau, Raphaël; Grignard, Bruno ULg et al

Conference (2015, July 06)

The present research aims at developing new very efficient organocatalysts for the chemical fixation of carbon dioxide onto epoxides that are precursors of non-isocyanate polyurethanes (NIPUs). Although ... [more ▼]

The present research aims at developing new very efficient organocatalysts for the chemical fixation of carbon dioxide onto epoxides that are precursors of non-isocyanate polyurethanes (NIPUs). Although this area of research is the subject of many works, the catalytic performance must be further enhanced in particular for the carbonatation of vegetable-based precursors while respecting environmental standards. In this context, we developed a new organocatalytic platform based on the combination of ammonium salts with single or double hydrogen bond donor activators that showed unexpected catalytic activity for the fast addition of CO2 onto epoxidized oils under mild conditions. First of all, in situ kinetic studies of the cycloaddition of CO2 onto model epoxidized oils were monitored by FT-IR spectroscopy in order to evaluate the influence of the hydrogen bond structure and various parameters such as the pressure, the temperature, the catalyst loading, and the nature of the epoxide on the reaction kinetics. Thanks to this catalyst screening, we found that ammonium salt/fluorinated hydrogen bond donors bicomponent organocatalysts were by far more efficient than that proposed in the literature under mild conditions (60°C, 2MPa). Then, the reaction mechanism of the organocatalyzed cycloaddition of propylene oxide onto CO2 was elucidated by performing Density Functional Theory (DFT). Our theoretical results highlighted the key role of the hydrogen bond interaction between the epoxide and the activators for the enhancement of the catalytic platform’s efficiency. [less ▲]

Detailed reference viewed: 99 (6 ULg)
Full Text
Peer Reviewed
See detailFluorinated alcohols as activators for the solvent-free chemical fixation of carbon dioxide onto epoxides
Gennen, Sandro ULg; Alves, Margot ULg; Méreau, Raphaël et al

in ChemSusChem (2015), 8(11), 1845-1849

The addition of fluorinated alcohols to onium salts provides highly efficient organocatalysts for the chemical fixation of CO2 onto epoxides under mild experimental conditions. The combination of online ... [more ▼]

The addition of fluorinated alcohols to onium salts provides highly efficient organocatalysts for the chemical fixation of CO2 onto epoxides under mild experimental conditions. The combination of online kinetic studies, NMR titrations and DFT calculations allows understanding this synergistic effect that provides an active organocatalyst for CO2/epoxides coupling. [less ▲]

Detailed reference viewed: 71 (21 ULg)
See detailNon-isocyanate polyurethane: from the monomer synthesis to foamed materials
Gennen, Sandro ULg; Alves, Margot ULg; Tassaing, Thierry et al

Poster (2015, May 18)

Polyurethane (PU) is one of the most important polymers in our everyday life with numerous applications such as thermosets, thermoplastics, elastomers, adhesives, sealants, coatings, rigid and flexible ... [more ▼]

Polyurethane (PU) is one of the most important polymers in our everyday life with numerous applications such as thermosets, thermoplastics, elastomers, adhesives, sealants, coatings, rigid and flexible foams... Classically, PUs are produced by a step-growth polymerization between diols and diisocyanates. However, isocyanates are harmful upon prolonged exposure to vapours which can lead to health issues such as asthma and skin irritation. In addition, isocyanates are produced from even more toxic and explosive phosgene. Due to these problems in combination with increasing regulatory scrutiny, there is today a need to develop isocyanate- and phosgene free- PU synthesis, also called non-isocyanate polyurethane or NIPUs. One of the most promising alternatives to the conventional synthesis of PU relies on the step-growth polymerization between bicyclic carbonate monomers and diamines, but until now, obtaining high molar mass NIPUs in a short time still remains a challenge. This study will be focused on three objectives: 1) The synthesis of CO2-sourced biscyclic carbonates by CO2/epoxide coupling using new highly efficient bicomponent organocatalysts allowing the fast conversion of epoxides into the corresponding cyclic carbonates under mild and solvent-free conditions. 2) The synthesis of high molar mass NIPUs from CO2-sourced monomers and diamines thanks to the use of efficient organocatalysts. A series of organic compounds interacting with cyclic carbonates by hydrogen bonding were first identified and their catalytic activity was highlighted by a model reaction between ethylene carbonate and a primary amine before extrapolation to NIPU synthesis. 3) The scCO2-assisted foaming of CO2-sourced NIPUs with production of potential carbon zero-emission materials with low thermal conductivity [less ▲]

Detailed reference viewed: 278 (5 ULg)
See detailNew efficient bicomponent organocatalysts for the chemical fixation of CO2 onto epoxides: a theoretical study
Alves, Margot ULg; Méreau, Raphaël; Grignard, Bruno ULg et al

Poster (2015, May 18)

Regarding the economic and environmental issues, valorising CO2 as a C1 feedstock for producing useful building blocks is seducing as it is a free and abundant waste resulting from the human activity ... [more ▼]

Regarding the economic and environmental issues, valorising CO2 as a C1 feedstock for producing useful building blocks is seducing as it is a free and abundant waste resulting from the human activity. Cyclic carbonates are useful compounds that found application as green solvents, electrolytes for lithium battery or monomers for polycarbonates or polyurethanes synthesis. These cyclocarbonates can be synthesized with a total atom economy by chemical fixation of CO2 onto epoxides using organometallic complexes or organocatalysts. To date, although this area of research has been the subject of many studies, the identification and development of (organo)catalysts highly efficient under mild experimental conditions still remains challenging. In this context, we developed a new organocatalytic platform based on the use of ammonium salts in combination with single or double hydrogen bond donor activators derived from fluorinated alcohols that showed unexpected booster effect. In this contribution, the ammonium/fluoroalcohol promoted CO2/propylene oxide coupling was investigated through detailed kinetic studies by IR spectroscopy under pressure and results were compared to the most efficient organocatalysts based on ammonium salts and (multi)phenolic derivatives that were reported in the literature. In order to finely understand the reaction mechanism, this study was completed by molecular modeling. DFT calculations showed that the addition of H-bond donors (HBD) with hexafluoroisopropanol functionalities modified the mechanism of the ammonium promoted coupling of CO2 with epoxides. HBDs dramatically decreased the epoxide ring-opening step barrier which highlights the key role of the fluorinated activators in stabilizing the intermediates and transitions states by inter- and intra-molecular hydrogen bonds. [less ▲]

Detailed reference viewed: 125 (3 ULg)
See detailDesign of new multifunctional nanocarriers for protein delivery
Parilti, Rahmet ULg; Jérôme, Christine ULg; Howdle, Steven M. et al

Conference (2015, May 18)

Polymeric nanoparticles have been extensively investigated for their biomedical applications especially as drug carriers. However, efficient encapsulation and delivery of therapeutic proteins in targeted ... [more ▼]

Polymeric nanoparticles have been extensively investigated for their biomedical applications especially as drug carriers. However, efficient encapsulation and delivery of therapeutic proteins in targeted manner still present challenges. This project aims to develop a novel one-pot strategy to obtain nanoparticles able to carry proteins in their core, as well as bearing targeting and/or imaging agents on their surface. In addition to this objective, polymerizations are carried out in supercritical carbon dioxide (scCO2), which confers environmentally benign features to the process. Dispersion polymerizations of hydrophilic monomer 2-hydroxyethyl methacrylate (HEMA) in are carried out in scCO2 in the presence of an initiator, cross-linker and CO2-philic photoclevable stabilizer. Upon exposure to UV light, the o-nitrobenzyl junctions present at the surface of the particles are cleaved, thus providing water dispersible hydrogels. Spherical monodisperse nanoparticles were successfully synthesized in scCO2 with two different conditions. Milder reaction conditions were achieved by using 2,2'-Azobis(4-methoxy-2,4-dimethyl valeronitrile (V70) as an initiator which opens up the platform for one-pot protein encapsulation in scCO2. [less ▲]

Detailed reference viewed: 99 (6 ULg)
See detailCarbon dioxide, a cheap bio-sourced building block for cyclic carbonates and non-isocyanate polyurethanes
Gennen, Sandro ULg; Alves, Margot ULg; Tassaing, Thierry et al

Poster (2015, May 03)

Due to concerns about global warming combined with the decrease of fossil resources, new carbon feedstocks that are abundant, renewable, non-toxic, inexpensive and environmentally friendly must be ... [more ▼]

Due to concerns about global warming combined with the decrease of fossil resources, new carbon feedstocks that are abundant, renewable, non-toxic, inexpensive and environmentally friendly must be explored to produce chemicals. Besides the valorization of bio-based raw materials, the chemical transformation of carbon dioxide into added-value products has gained interest in both academia and industry. To date, the chemical fixation of CO2 onto epoxides with the formation of cyclic carbonates is one of the most promising ways to valorize CO2 at an industrial scale. Indeed, cyclic carbonates find applications as electrolytes in lithium ion batteries, as aprotic polar solvents or as useful intermediates for polycarbonates. Cyclic carbonates also react with primary amines to produce 2-hydroxyethylurethane. This reaction can be extrapolated to the synthesis of non-isocyanate polyurethanes (NIPU) by polyaddition of bifunctional cyclic carbonates with diamines.5 This study aims (i) at developing a new highly efficient organocatalyst for the synthesis of cyclic carbonates under mild experimental conditions and (ii) their valorization as monomers to produce non-isocyanate polyurethanes. First, we have identified a bicomponent organocatalyst, composed of a judicious combination of an organocatalyst and an activator, for the very fast synthesis of cyclic carbonates from CO2 and epoxides under very mild reaction conditions. Kinetics of reactions were followed by online Raman spectroscopy measurements under pressure. NMR titrations were realized to evidence the mechanism of activation of this novel organocatalytic system that will be discussed in detail in this talk. The second objective relies on the development of new efficient organocatalysts for the synthesis of high molar masses NIPUs in short reaction times. Organic compounds interacting with the cyclic carbonate by hydrogen bonding were identified and their catalytic activity was demonstrated for model compounds. [less ▲]

Detailed reference viewed: 198 (2 ULg)
See detailNew efficient organocatalyst for the synthesis of bio-based cyclic carbonates from CO2 and vegetable oil
Alves, Margot ULg; Gennen, Sandro ULg; Grignard, Bruno ULg et al

Conference (2015, May)

Recently, a “greener” approach has been developed to produce bio-sourced polyurethanes by reaction of bio-based cyclic carbonates and amines. Bio-based cyclic carbonates can be synthesised with a total ... [more ▼]

Recently, a “greener” approach has been developed to produce bio-sourced polyurethanes by reaction of bio-based cyclic carbonates and amines. Bio-based cyclic carbonates can be synthesised with a total atom economy by chemical fixation of carbon dioxide onto an epoxidized vegetable oil using an appropriate catalyst. Thus, although this area of research has been the subject of many works, catalytic performance must be further enhanced in particular for the carbonatation of vegetable-based precursors while respecting environmental standards. The aim of the present work is to propose new organocatalytic platforms enabling the cycloaddition of CO2 onto epoxidized oils in the most efficient way under mild conditions. For such task, in situ kinetic follow-up of the cycloaddition of model epoxides and epoxidized oils onto CO2 has been performed by FT-IR spectroscopy in order to determine the catalytic activity of new binary organocatalytic systems and to evaluate the influence of various parameters (pressure, temperature catalyst concentration, nature of the epoxide) on the yields and the reaction kinetics. The binary organocatalytic platform is composed of an ammonium salt combined with hydrogen-bond donors. Thanks to this catalyst screening, we have found that new organocatalytic platforms were by far more efficient than that proposed in the literature. Then, few catalytic systems have been investigated by molecular modeling in order to understand the reaction mechanism. The theoretical results put in evidence the key role of the hydrogen bond interaction between the epoxide and the co-catalyst for the enhancement of the catalytic platform’s efficiency. [less ▲]

Detailed reference viewed: 27 (3 ULg)
See detailCarbon dioxide and vegetable ooil for the synthesis of bio-based polymer precursor
Alves, Margot ULg; Méreau, Raphaël; Grignard, Bruno ULg et al

Conference (2015, March 18)

Detailed reference viewed: 39 (7 ULg)
Full Text
Peer Reviewed
See detailSmall Angle X-ray Scattering Insights into the Architecture-Dependent Emulsifying Properties of Amphiphilic Copolymers in Supercritical Carbon Dioxide
Alaimo, David ULg; Hermida Merino, Daniel; Grignard, Bruno ULg et al

in Journal of Physical Chemistry B (2015), 119

The supramolecular assembly of a series of copolymers combining a PEO-rich hydrophilic and fluorinated CO2-philic sequences is analysed by synchrotron small-angle xray scattering (SAXS) in supercritical ... [more ▼]

The supramolecular assembly of a series of copolymers combining a PEO-rich hydrophilic and fluorinated CO2-philic sequences is analysed by synchrotron small-angle xray scattering (SAXS) in supercritical CO2, as well as in water/CO2 emulsions. These copolymers were designed to have the same molecular weight and composition, and to differ only by their macromolecular architecture. The investigated copolymers have random, block, and palm-tree architectures. Besides, thermo-responsive copolymer is also analysed, having a hydrophilic sequence becoming water-insoluble around 41 °C, i.e. just above the critical point of CO2. At the length scale investigated by SAXS, only the random copolymer appears to self-assemble in pure CO2, in the form of a disordered microgel-like network. The random, block and thermo-responsive copolymers are all able to stabilize water/CO2 emulsions but not the copolymer with the palm-tree architecture, pointing at the importance of macromolecular architecture for the emulsifying properties. A modelling of the SAXS data shows that the block and the thermo-responsive copolymers form spherical micelle-like structures containing about 70 % water and 30 % polymer. [less ▲]

Detailed reference viewed: 264 (22 ULg)