References of "Jérôme, Christine"
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See detailDouble hydrophilic polyphosphoester containing copolymers as efficient templating agents for calcium carbonate microparticles
Ergül, Zeynep ULg; Debuigne, Antoine ULg; Calvignac, Brice et al

in Journal of Materials Chemistry B (2015), 3(36), 7227-7236

The use of calcium carbonate (CaCO3) microparticles is becoming more and more attractive in many fields especially in biomedical applications in which the fine tuning of the size, morphology and ... [more ▼]

The use of calcium carbonate (CaCO3) microparticles is becoming more and more attractive in many fields especially in biomedical applications in which the fine tuning of the size, morphology and crystalline form of the CaCO3 particles is crucial. Although some structuring compounds, like hyaluronic acid, give satisfying results, the control of the particle structure still has to be improved. To this end, we evaluated the CaCO3 structuring capacity of novel well-defined double hydrophilic block copolymers composed of poly(ethylene oxide) and a polyphosphoester segment with an affinity for calcium like poly(phosphotriester)s bearing pendent carboxylic acids or poly(phosphodiester)s with a negatively charged oxygen atom on each repeating monomer unit. These copolymers were synthesized by a combination of organocatalyzed ring opening polymerization, thiol–yne click chemistry and protection/deprotection methods. The formulation of CaCO3 particles was then performed in the presence of these block copolymers (i) by the classical chemical pathway involving CaCl2 and Na2CO3 and (ii) by a process based on supercritical carbon dioxide (scCO2) technology in which CO32− ions are generated in aqueous media and react with Ca2+ ions. Porous CaCO3 microspheres composed of vaterite nanocrystals were obtained. Moreover, a clear dependence of the particle size on the structure of the templating agent was emphasized. In this work, we show that the use of the supercritical process and the substitution of hyaluronic acid for a carboxylic acid containing copolymer decreases the size of the CaCO3 particles by a factor of 6 (∼1.5 μm) while preventing their aggregation. [less ▲]

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See detailInfluence of the macromolecular surfactant features and reactivity on morphology and surface properties of emulsion-templated porous polymers
Mathieu, Kevin ULg; Jérôme, Christine ULg; Debuigne, Antoine ULg

in Macromolecules (2015), 48(18), 6489-6498

This work investigates key parameters of a straightfor- ward macromolecular surfactant-assisted functionalization strategy of porous polymers produced by high internal phase emulsion (HIPE) polymerization ... [more ▼]

This work investigates key parameters of a straightfor- ward macromolecular surfactant-assisted functionalization strategy of porous polymers produced by high internal phase emulsion (HIPE) polymerization. For that purpose, a series of well-defined amphiphilic poly(ethylene oxide)-b-poly(styrene) (PEO-b-PS) copolymers with various compositions and molar masses were synthesized by radical addition−fragmentation chain transfer (RAFT) polymerization and used as macromolecular surfactants for the emulsion-templated polymerization of styrene/divinylbenzene (S/DVB). The morphology of the resulting foams, referred to as polyHIPEs, was found dependent on the PS block length and concentration of the block copolymer surfactant in the emulsion. Moreover, we determined the lowest PS block length required for preserving the anchoring of the copolymer at the surface by physical entanglement within the S/DVB cross-linked matrix leading to a PEO-coated porous material. The functionalization of the porous monoliths with PEO was evidenced by sessile drop shape analyses and water uptake experiments. The chemical anchoring of the PEO-b-PS at the surface of polyHIPEs was also explored by interfacial initiation of the HIPE polymerization from a PEO-b-PS-RAFT macroinitiator leading to porous structures with permanent PEO coatings. In this case, copolymerizing DVB with acrylate instead of styrene improved the interconnectivity of the porous monoliths. [less ▲]

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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 ▲]

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See detailCobalt-mediated radical polymerization for the precision design of novel poly(ionic liquid) copolymers in aqueous media
Cordella, Daniela ULg; Kermagoret, Anthony; Debuigne, Antoine ULg et al

Poster (2015, September 11)

Poly(ionic liquid)s (PILs) have emerged as a special class of polyelectrolyte materials, featuring tunable solubility, high ionic conductivity, and a broad range of glass transition temperatures. Due to ... [more ▼]

Poly(ionic liquid)s (PILs) have emerged as a special class of polyelectrolyte materials, featuring tunable solubility, high ionic conductivity, and a broad range of glass transition temperatures. Due to their specific properties emanating from the ionic liquid (IL) units and their intrinsic polymeric nature, PILs find potential applications in various areas, such as analytical chemistry, biotechnology, gas separation, dispersants, solid ionic conductors for energy, catalysis, etc. In recent years, controlled radical polymerization (CRP) techniques have been applied to the synthesis of structurally well-defined PILs, with control attained over molar mass, dispersity, and end-group fidelity. In this poster, we will report on the implementation of cobalt-mediated radical polymerization (CMRP) technique for the precision synthesis of unprecedented PILs (co)polymers. We will discuss how an organocobalt complex can efficiently control the growth of vinyl imidazolium chains and lead to PILs with predicted molar masses and low polydispersities under mild experimental conditions, thus at low temperature and using water as a green polymerization medium. The huge potential of this system will be highlighted by describing the one-pot synthesis of all vinyl imidazolium-based block copolymers in aqueous media. This CMRP is unique for providing well-defined vinyl imidazolium based-copolymers for advanced PILs applications. [less ▲]

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See detailNovel organocobalt for the synthesis of functional polymers
Demarteau, Jérémy ULg; Kermagoret, Anthony; Jérôme, Christine ULg et al

Poster (2015, September 11)

Organocobalt(III) with acetylacetonate (acac) ligands is the most representative example of R-Co bearing a labile C-Co bond that can release alkyl radicals under mild experimental conditions without ... [more ▼]

Organocobalt(III) with acetylacetonate (acac) ligands is the most representative example of R-Co bearing a labile C-Co bond that can release alkyl radicals under mild experimental conditions without requiring a photoactivation. The unique isolated R-Co is a short oligo(vinyl acetate) end-capped by Co(acac)2. The high lability of its C-Co bond combined to the unique capacity of Co(acac)2 to reversibly trap alkyl radicals make this R-Co unique for the precision design of unprecedented polymers by Cobalt-Mediated Radical Polymerization (CMRP). The growth of unstabilized and highly reactive growing radicals formed by the addition of R• to unconjugated vinyl monomers (vinyl esters, vinyl amides, vinyl imidazolium, vinyl chloride, etc;) is controlled by the reversible formation of a weak C-Co bond at the polymer chain end. The lack of alternatives to this R-Co, especially to the structure of the alkyl group, has however placed limitations on post-functionalizations of end-chains. Other functional variants that would enable attractive chain-end derivatizations are unfortunately not available. In this poster, we will address this important challenge by describing an innovative synthetic route towards the preparation of new functional R-Co(acac)2 that are sources of halomethyl radicals under mild experimental conditions. The efficiency of these novel organocobalt complexes for the precision synthesis of end-functional and telechelic polymers will be described. Also, the solubility of these complexes in water enables the facile production of end-functionalized water soluble poly(ionic liquid)s. Further derivatizations of the halomethyl group at the chain-end of polymers produced by this system will be demonstrated by click reaction, largely broadening the range of possible functional groups. Finally, besides numerous applications in macromolecular engineering, this unexplored family of R-Co presents a high potential in radical reactions in organic synthesis by the facile production of halomethyl radicals. [less ▲]

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See detailIntercalation of imidazolium end-functionalized polyphosphates between montmorillonite nanosheets towards flame-retardant
Carion, Stéphan ULg; Lecomte, Philippe ULg; Thomassin, Jean-Michel ULg et al

Poster (2015, September 11)

Among the additives used to impart flame-retardant properties to polymer materials, phosphorous additives and nanoclays are widely used. The aim of this work is to associate both additives to bring about ... [more ▼]

Among the additives used to impart flame-retardant properties to polymer materials, phosphorous additives and nanoclays are widely used. The aim of this work is to associate both additives to bring about a synergetic effect for improving the flame-retardancy of the material (1). In a first step, the synthesis of an aliphatic polyphosphate end-capped by an imidazolium cation is reported. Secondly, this polymer is intercalated between montmorillonite nanoclays. The strategy used for the synthesis of the polyphosphate is based on the ring-opening polymerization of the corresponding cyclic phosphate by using 1-(11-hydroxy-undecyl)-3-methylimidazolium bromide as an initiator. This polymerization was catalyzed by DBU and a thiourea derivative (2). This polymer was characterized by a set of techniques (31P and 1H NMR, SEC, TGA, DSC). Finally, the cationic end-functionalized polymer was exchanged with sodium cations present in montmorillonite. The intercalation of the polyphosphate between the clay nanosheets was proved by X-Ray Diffraction (XRD) and thermogravimetric analysis (TGA). This last technique was also used to determine the influence of the intercalation on the thermal stability of the polyphosphate. [less ▲]

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See detailLow bandgap copolymers based on monofluorinated isoindigo towards efficient polymer solar cells
Tomassetti, Mirco ULg; Ouhib, Farid ULg; Wislez, Arnaud ULg et al

in Polymer Chemistry (2015), 6(33), 6040-6049

To explore the effectiveness of monofluorinated isoindigo as an electron-deficient building block in push–pull conjugated polymers for organic solar cell applications, four low bandgap copolymers are ... [more ▼]

To explore the effectiveness of monofluorinated isoindigo as an electron-deficient building block in push–pull conjugated polymers for organic solar cell applications, four low bandgap copolymers are effectively synthesized and characterized. The effects of fluorine introduction, thiophene spacer length and polymer molar mass on the general electro-optical polymer characteristics, thin film blend micro- structure and electronic performance are investigated. Isoindigo monofluorination effectively improves the power conversion efficiency from 2.8 up to 5.0% upon molar mass optimization, without using any processing additives or post-treatments. [less ▲]

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See detailDevelopment of photo- or thermo-reversible cross-linked recyclable shape-memory materials
Defize, Thomas ULg; Riva, Raphaël ULg; Thomassin, Jean-Michel ULg et al

Conference (2015, September 01)

Shape-memory polymers (SMPs) are remarkable materials able to switch from a stressed deformed state (temporary shape) to their initial relaxed state (permanent shape) by the application of a stimulus ... [more ▼]

Shape-memory polymers (SMPs) are remarkable materials able to switch from a stressed deformed state (temporary shape) to their initial relaxed state (permanent shape) by the application of a stimulus, such as heat or light. Typically, the shape-memory property is generally observed for chemically or physically cross-linked polymers that exhibit an elastomeric behavior above a phase transition, e.g. glass or melting transition. As an example, cross-linked semi-crystalline poly(ε-caprolactone) (PCL) is widely studied for the development of SMPs. As most of SMPs are irreversibly cross-linked material, their reprocessing is impossible preventing any recycling. Thereby, reversible reactions, allowing the formation/cleavage of the network, raise tremendous interest for the development of new SMPs. Recently, we reported the preparation reversibly cross-linked PCL-based SMP using the Diels-Alder (DA) reaction between furan and maleimide end-groups of 4-arm star-shaped PCL, well-known to create reversible bonds. After implementation, this shape-memory material was demonstrated to be recyclable, and was characterized by excellent fixity and recovery before and after recycling experiments. However, the relatively low retro DA temperature of the furan-maleimide adducts led to an inelastic deformation during shape-memory tensile cycles. In order to get rid of this drawback, an alternative approach was investigated. The substitution of the DA reaction by a photo-reversible reaction, typically the photo-induced (2+2) cycloaddition of coumarins, was proposed to prepare cross-linked PCL matrix presenting one-way and two-way memory properties, since photolabile adducts are supposed to be stable during shape-memory tensile cycles. [less ▲]

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See detailCross-linked polymer micelles made of polyphosphate containing amphiphilic copolymers for drug delivery
Riva, Raphaël ULg; Vanslambrouck, Stéphanie ULg; Ergül, Zeynep ULg et al

Conference (2015, September 01)

In the pharmaceutical field, amphiphilic block copolymers are of great interest for the nanovectorization of active principles in Drug Delivery. Indeed, new drugs are synthesized each day but in too many ... [more ▼]

In the pharmaceutical field, amphiphilic block copolymers are of great interest for the nanovectorization of active principles in Drug Delivery. Indeed, new drugs are synthesized each day but in too many cases, their high hydrophobicity makes them useless because of the absence of an appropriated administration method. Typically, amphiphilic block copolymers present the remarkable property to self-assemble in water with formation, in most cases, of spherical micelles characterized by a hydrophobic core and a hydrophylic corona. Rapidly, their ability to encapsulate a hydrophobic drug in their hydrophiobic core was investigated to increase the solubility of the drug in aqueous media, prevent its degradation and decrease its toxicity. However, polymer micelles suffer of the main drawback to be unstable in diluted medium, leading to a premature release of the drug, when the concentration falls down the critical micellar concentration (CMC), which it is rapidly observed after intravenous injection. This work aims at reporting on the development of a drug delivery device based on a new amphiphilic block copolymers made of degradable polyphosphate and bioeliminable poly(ethylene oxide). Thanks to their biocompatibility, biodegradability and their structure similar to natural biomacromolecules, polyphosphates are appealing polymers for biomedical applications. In contrast to aliphatic polyesters, polyphosphate properties and functionality are easily tuned via the chemical nature of the lateral chains R. In order to get rid of the CMC, the crosslinking of the micelle’s core was realized by UV radiation, in order to fulfill the increasingly stringent requirements of biomedical applications. For this purpose, photo-cross-linkable groups were introduced on the polyphosphate backbone. The effect of the crosslinking rate on the drug loading and the drug release was evaluated using doxorubicin as model drug. [less ▲]

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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 ▲]

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See detailOrganometallic-mediated radical polymerization for the precision design of novel poly(ionic liquid) copolymers in water
Cordella, Daniela ULg; Kermagoret, Anthony; Debuigne, Antoine ULg et al

Conference (2015, August 18)

In recent years, poly(ionic liquid)s (PIL)s were found to take an enabling role in important fields of polymer chemistry and material science. PILs combine the unique properties of ionic liquids with the ... [more ▼]

In recent years, poly(ionic liquid)s (PIL)s were found to take an enabling role in important fields of polymer chemistry and material science. PILs combine the unique properties of ionic liquids with the flexibility and properties of macromolecular architectures giving rise to a new family of functional polymers that opens new area of applications such as polymer electrolytes in electrochemical devices, powerful dispersants and stabilizers, absorbing membranes, precursors for carbon materials, porous polymers, etc. Controlled radical polymerization techniques have recently emerged as powerful tools for the precision design of novel PILs architectures and functionalities, enabling a considerable extension of the applications of PILs with the emergence of new properties. Many efforts are devoted to tentatively control the radical polymerization of ionic liquid monomers (ILs) that directly leads to PILs without requiring further polymer derivatization. Poly(vinyl imidazolium)s belong to a class of PILs of high interest but the control radical polymerization of their corresponding monomer is touchy due to the high reactivity of their propagating radical. In this communication, we will report on the implementation of organometallic-mediated radical polymerization (OMRP) technique for the precision synthesis of unprecedented PILs (co)polymers by direct polymerization of ILs in water. We will first discuss how a commercially available cobalt complex can efficiently control the growth of poly(vinyl imidazolium) chains and lead to PILs with predicted molar masses and low dispersities under mild experimental conditions. The efficiency of the process will then be illustrated by the one-pot synthesis of vinyl imidazolium-based block copolymers in aqueous media. This OMRP technique, highly compatible to water and active under moderate temperatures (30-40°C), is unique for providing well-defined vinyl imidazolium based-copolymers and novel PILs assemblies, and open new application fields. [less ▲]

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See detailDesign of hybrid nanovehicles for remotely triggered drug release: an overview
Liu, Ji; Detrembleur, Christophe ULg; Mornet, Stéphane et al

in Journal of Materials Chemistry B (2015), 3(30), 6117-6147

n the past few decades, various nanovehicles have been developed as drug delivery systems, in which inorganic and organic components are integrated within a nano-object. Upon the application of remote ... [more ▼]

n the past few decades, various nanovehicles have been developed as drug delivery systems, in which inorganic and organic components are integrated within a nano-object. Upon the application of remote stimuli, e.g. alternating magnetic field, near infrared or ultrasound radiations, the release of guest molecules can be triggered in a quite controlled manner. Herein, we review different hybrid nanostructures which have already been reported for the remotely triggered release, such as those based on (1) host–guest conjugates, (2) core–corona nanoparticles, (3) polymer nanogels, (4) polymer micelles, (5) liposomes, (6) mesoporous silica particles and (7) hollow nanoparticles. Moreover, we also summarize six underlying mechanisms that govern such a kind of remotely triggered release behaviours: (1) enhanced diffusion and/or permeation, (2) thermo- or photo-labile bond cleavage, (3) fusion of phase-changed materials, (4) photo-induced isomerisation, (5) thermo-induced swelling/de-swelling of thermo-responsive polymers, and (6) destruction of the nanostructures. The ways in which different components are incorporated into an integrated hybrid nanostructure and how they contribute to the remotely triggered release behaviours are detailed. [less ▲]

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See detailAll Poly(ionic liquid)-based block copolymers by sequential controlled radical copolymerization of vinylimidazolium monomers
Cordella, Daniela ULg; Kermagoret, Anthony; Debuigne, Antoine ULg et al

in Macromolecules (2015), 48(15), 5230-5243

The organometallic-mediated radical polymerization (OMRP) of N-vinyl-3-alkylimidazolium-type monomers, featuring the bis(trifluoromethylsulfonyl)imide counteranion (Tf2N–), in the presence of Co(acac)2 as ... [more ▼]

The organometallic-mediated radical polymerization (OMRP) of N-vinyl-3-alkylimidazolium-type monomers, featuring the bis(trifluoromethylsulfonyl)imide counteranion (Tf2N–), in the presence of Co(acac)2 as controlling agent, is reported. Polymerizations of monomers with methyl, ethyl, and butyl substituents are fast, reaching high monomer conversion in ethyl acetate as solvent at 30 °C, and afford structurally well-defined hydrophobic poly(ionic liquid)s (PILs) of N-vinyl type. Block copolymer synthesis is also achieved by sequential OMRP of N-vinyl-3-alkylimidazolium salts carrying different alkyl chains and different counteranions (Tf2N– or Br–). These block copolymerizations are carried out at 30 °C, either under homogeneous solution in methanol or in a biphasic medium consisting of a mixture of ethyl acetate and water. Unprecedented PIL-b-PIL block copolymers are thus prepared under these conditions. However, anion exchange occurs at the early stage of the growth of the second block. Finally, diblock copolymers generated in the biphasic medium can be readily coupled by addition of isoprene, forming all PIL-based and symmetrical ABA-type triblock copolymers in a one-pot process. Such a direct block copolymerization method, involving vinylimidazolium monomers bearing different alkyl chains, thus opens new opportunities in the precision synthesis of all PIL-based block copolymers of tunable properties. [less ▲]

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See detailDrug loading of polymer implants by supercritical CO2 assisted impregnation: a review
Champeau, Mathilde; Thomassin, Jean-Michel ULg; Tassaing, Thierry et al

in Journal of Controlled Release (2015), 209

Drug loaded implants also called drug-eluting implants have proven their benefits over simple implants. Among the developed manufacturing processes, the supercritical CO2 (scCO2) assisted impregnation has ... [more ▼]

Drug loaded implants also called drug-eluting implants have proven their benefits over simple implants. Among the developed manufacturing processes, the supercritical CO2 (scCO2) assisted impregnation has attracted growing attention to load Active Pharmaceutical Ingredients into polymer implants since it enables to recover a final implant free of any solvent residue and to operate under mild temperature which is suitable for processing with thermosensitive drugs. This paper is a review of the state-of-the-art and the application of the scCO2 assisted impregnation process to prepare drug-eluting implants. It introduces the process and presents its advantages for biomedical applications. The influences of the characteristics of the implied binary systems and of the experimental conditions on the drug loading are described. Then, the various current applications of this process for manufacturing drug-eluting implants are reviewed. Finally, the new emerging variations of this process are described. [less ▲]

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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 ▲]

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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 ▲]

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See detailPhoto- and thermo-reversible crosslinked recyclable shape memory materials
Defize, Thomas ULg; Riva, Raphaël ULg; Thomassin, Jean-Michel ULg et al

Poster (2015, July 02)

Shape memory polymers (SMPs) are remarkable materials able to switch from a stressed deformed state (temporary shape) to their initial relaxed state (permanent shape) by the application of a stimulus ... [more ▼]

Shape memory polymers (SMPs) are remarkable materials able to switch from a stressed deformed state (temporary shape) to their initial relaxed state (permanent shape) by the application of a stimulus; such as heat or light. Typically; the shape memory property is generally observed for chemically or physically cross-linked polymers that exhibit an elastomeric behavior above a phase transition; e.g. glass or melting transition. As an example; cross-linked semi-crystalline poly(ε-caprolactone) (PCL) is widely studied for the development of SMPs. As most of SMPs are irreversibly cross-linked material; their reprocessing is impossible preventing any recycling. Thereby; reversible reactions; allowing the formation/cleavage of the network; raise tremendous interest for the development of new SMPs. Recently, we reported the preparation reversibly cross-linked PCL-based SMP using the Diels-Alder (DA) reaction between furan and maleimide end-groups of 4-arm star-shaped PCL, well-known to create reversible bonds. After implementation, this shape memory material was demonstrated to be recyclable, and was characterized by excellent fixity and recovery before and after recycling experiments. However, the relatively low retro DA temperature of the furan-maleimide adducts led to an inelastic deformation during shape memory tensile cycles. In order to get rid of this drawback, an alternative approach was investigated. The substitution of the DA reaction by a photo-reversible reaction, typically the photo-induced (2+2) cycloaddition of coumarins, was proposed to prepare cross-linked PCL matrix presenting one-way and two-way memory properties, since photolabile adducts are supposed to be stable during shape memory tensile cycles. [less ▲]

Detailed reference viewed: 109 (9 ULg)