References of "Calberg, Cédric"
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See detailPreparation of living polymer microspheres by dispersion atom transfer radical polymerization in scCO2 using fluorinated macroligands
Grignard, Bruno ULg; Calberg, Cédric ULg; Jérôme, Christine ULg et al

Poster (2009, May 19)

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 styrene, to the synthesis of diblock copolymers beads and the controlled synthesis of hyperbranched copolymers. Finally, 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. [less ▲]

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See detailSupercritical CO2 as an efficient medium for layered silicate organomodification: preparation of thermally stable organoclays and dispersion in polyamide 6
Naveau, Elodie ULg; Calberg, Cédric ULg; Detrembleur, Christophe ULg et al

in Polymer (2009), 50(6), 1438-1446

In this study, the preparation of organoclays via a new process using supercritical carbon dioxide is described. This method turns out to be very efficient with various surfactants, in particular nonwater ... [more ▼]

In this study, the preparation of organoclays via a new process using supercritical carbon dioxide is described. This method turns out to be very efficient with various surfactants, in particular nonwater-soluble alkylphosphonium salts. The influence of the surfactant as well as of the clay nature on the thermal stability of the organoclay is evaluated by thermogravimetric analysis. Phosphonium-based montmorillonites are up to 90 °C more stable than ammonium-based montmorillonites. Moreover, the use of hectorite adds another 40 °C of thermal stability to the phosphonium-modified clays. These organomodified clays have been melt-blended with polyamide 6 and morphology as well as fire properties of the nanocomposites are discussed, in terms of influence of the stability of organoclays. For the first time, comparison of nanocomposites based on clay organomodified by ammonium and phosphonium salts of the very same structure is reported. [less ▲]

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See detailSynthesis of polylactide/clay nanocomposites by in situ intercalative polymerization in supercritical carbon dioxide
Urbanczyk, Laetitia ULg; Ngoundjo, Fred; Alexandre, Michaël ULg et al

in European Polymer Journal (2009), 45(3), 643-648

Polylactide (PLA)/clay nanocomposites have been prepared by in situ ring-opening polymerization in supercritical carbon dioxide. Depending on the type of organoclay used, polylactide chains can be grafted ... [more ▼]

Polylactide (PLA)/clay nanocomposites have been prepared by in situ ring-opening polymerization in supercritical carbon dioxide. Depending on the type of organoclay used, polylactide chains can be grafted onto the clay surface, leading to an exfoliated morphology. Nanocomposites with high clay contents (30–50 wt.%), called masterbatches, have also been successfully prepared and were recovered as fine powders thanks to the unique properties of the supercritical fluid. Dilution of these masterbatches into commercial l-polylactide by melt blending has led to essentially exfoliated nanocomposites containing 3 wt.% of clay. The mechanical properties of these materials have been assessed by flexion and impact tests. Significant improvements of stiffness and toughness have been observed for the PLA/clay nanocomposites compared to the pure matrix, together with improved impact resistance. [less ▲]

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See detailDesign of perfluorinated macroligand for the implementation of atom transfer radical polymerization in supercritical carbon dioxide
Grignard, Bruno ULg; Jérôme, Christine ULg; Calberg, Cédric ULg et al

Conference (2008, November 28)

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. The goal of the research relies on the development of ATRP of vinyl monomers in scCO2. Perfluorinated polymethacrylate, i.e. poly2,2,2-trifluoroethyl methacrylate (PFMA), was successfully prepared by homogenous ATRP using a polymeric ligand in order to complex the copper catalyst. CO2-soluble poly(2,2,2-trifluoroethylmethacrylate) was also prepared in supercritical CO2 by supported ATRP using a “pseudo-homogeneous” catalyst consisting of copper (I) ligated by macroligand immobilized onto an inorganic support, that results in polymers with well defined molecular weight and low polydispersity. 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 was also reported and the concept of dispersion ATRP was extended to the dispersion ATRP of styrene, to the synthesis of diblock copolymers beads using PMMA beads as macroinitiators, leading to (co)polymers with predictable molecular weight and narrow polydispersity. Finally, 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, leading to the formation of PMMA of well defined characteristics that was collected as fluorescent micropheres. [less ▲]

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See detailDispersion Atom Transfer Radical Polymerization of vinyl monomers in supercritical carbon dioxide
Grignard, Bruno ULg; Jérôme, Christine ULg; Calberg, Cédric ULg et al

in Macromolecules (2008), 41(22), 8575-8563

Controlled dispersion atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) was successfully carried out in supercritical carbon dioxide in the presence of aminated fluoropolymers ... [more ▼]

Controlled dispersion atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) was successfully carried out in supercritical carbon dioxide in the presence of aminated fluoropolymers. These materials played the dual role of macroligand for the copper bromide and also steric stabilizer to support formation of polymer microspheres. The livingness of the PMMA beads was confirmed by the one-pot two-step PMMA chain extension and the synthesis of poly(methyl methacrylate)-b-poly(2,2,2-trifluoroethyl methacrylate) (PMMA-b-PFMA) diblock copolymer in scCO2. Successful activator generated by electron transfer (AGET) for ATRP of MMA, using tin ethylhexanoate as a reducing agent, is also discussed, and the concept of dispersion ATRP of MMA was successfully extended to the controlled dispersion polymerization of styrene by ATRP leading to the formation of PS microparticles. Finally, due to the high solubility of the catalyst in scCO2, the purification of PMMA was investigated by supercritical fluid extraction, leading to the preparation of PMMA beads with low residual catalyst traces. [less ▲]

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See detailSynthesis of biodegradable poly-epsilon-caprolactone microspheres by dispersion ring-opening polymerization in supercritical carbon dioxide
Grignard, Bruno ULg; Stassin, Fabrice; Calberg, Cédric ULg et al

in Biomacromolecules (2008), 9(11), 3141-3149

A series of fluorinated diblock and triblock copolymers of poly(ε-caprolactone) and poly(heptadecafluorodecylacrylate) were prepared by combining ring-opening polymerization of ε-CL and atom transfer ... [more ▼]

A series of fluorinated diblock and triblock copolymers of poly(ε-caprolactone) and poly(heptadecafluorodecylacrylate) were prepared by combining ring-opening polymerization of ε-CL and atom transfer radical polymerization of the acrylate. These copolymers with well-controlled molecular weight and composition were characterized by 1H NMR spectroscopy and used as stabilizers for the dispersion ring-opening polymerization of ε-CL in supercritical carbon dioxide. The effect of composition and architecture of the polymeric stabilizers on the stabilization of PCL microspheres was investigated. Finally, purification of PCL was successfully implemented by reactive supercritical fluid extraction of the tin catalyst. [less ▲]

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See detailSynthesis of PCL/clay masterbatches in supercritical carbon dioxide
Urbanczyk, Laetitia ULg; Calberg, Cédric ULg; Stassin, Fabrice et al

in Polymer (2008), 49(18), 3979-3986

Pre-exfoliated nanoclays were prepared through a masterbatch process using supercritical carbon dioxide as solvent and poly(epsilon-caprolactone) as organic matrix. In situ polymerization of epsilon ... [more ▼]

Pre-exfoliated nanoclays were prepared through a masterbatch process using supercritical carbon dioxide as solvent and poly(epsilon-caprolactone) as organic matrix. In situ polymerization of epsilon-caprolactone in the presence of large amount of clay was conducted to obtain these easily dispersible nanoclays, collected as a dry and fine powder after reaction. Dispersion of these pre-exfoliated nanoclays in chlorinated polyethylene was also investigated. All the results confirm the specific advantages of supercritical CO2 towards conventional solvents for filler modification. [less ▲]

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See detailCharacterization of the porous structure of biodegradable scaffolds obtained with supercritical CO2 as foaming agent
Léonard, Angélique ULg; Calberg, Cédric ULg; Kerckhofs, Greet ULg et al

in Journal of Porous Materials (2008), 15(4), 397-403

Poly(ε-caprolactone) foams were prepared, via a batch process, by using supercritical CO2 as foaming agent. Their porous structure was characterized through mercury porosimetry, helium and mercury ... [more ▼]

Poly(ε-caprolactone) foams were prepared, via a batch process, by using supercritical CO2 as foaming agent. Their porous structure was characterized through mercury porosimetry, helium and mercury pycnometry, scanning electron microscopy (SEM) and X-ray microtomography observations coupled with image analysis. The pore size distributions obtained by these two latter techniques show that the pore structure is more homogeneous when the foaming process is performed under a high CO2 saturation pressure (higher than 250 bars). [less ▲]

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See detailPoly(caprolactone)/clay masterbatches prepared in supercritical CO2 as efficient clay delamination promoters in poly(styrene-co-acrylonitrile)
Urbanczyk, Laetitia ULg; Calberg, Cédric ULg; Benali, Samira et al

in Journal of Materials Chemistry (2008), 18(39), 4623-4630

Poly(styrene-co-acrylonitrile) (SAN)/clay nanocomposites with a high degree of clay exfoliation were prepared upon melt blending of pre-exfoliated poly(-caprolactone) (PCL)/organoclay masterbatches in a ... [more ▼]

Poly(styrene-co-acrylonitrile) (SAN)/clay nanocomposites with a high degree of clay exfoliation were prepared upon melt blending of pre-exfoliated poly(-caprolactone) (PCL)/organoclay masterbatches in a Brabender-type internal mixer. These highly filled masterbatches were synthesized by a one-pot process using supercritical carbon dioxide as a polymerization medium. During their dispersion into SAN, PCL is expected to act as a compatibilizer at the polymer–clay interface as it is miscible with the host matrix under these conditions. Reference nanocomposites based on direct melt mixing of the commercial organoclay were also prepared for the sake of comparison. The superiority of the masterbatch route in term of clay delamination efficiency has been evidenced by XRD analysis, visual and TEM observations. The effect of the nanocomposite morphology on the polymer properties was then investigated. A substantial improvement of the fire behaviour and a decrease in gas permeability have been observed for the nanocomposite containing the highest level of clay exfoliation, accompanied with a higher brittleness as evidenced by traction and impact tests. [less ▲]

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See detailSupercritical carbon dioxide, a tool for the dispersion ROP of lactone and PCL foaming: Part A
Grignard, Bruno ULg; Urbanczyk, Laetitia ULg; Stassin, Fabrice et al

Poster (2008, June 02)

Aliphatic polyesters, namely polylactide (PLA) and poly-ε-caprolactone (PCL) are biodegradable and biocompatible materials that find applications as resorbable suture (PLA) and drugs delivery vectors (PCL ... [more ▼]

Aliphatic polyesters, namely polylactide (PLA) and poly-ε-caprolactone (PCL) are biodegradable and biocompatible materials that find applications as resorbable suture (PLA) and drugs delivery vectors (PCL). Nevertheless, these polymers were mainly prepared by ring opening polymerization using aluminum alkoxide or tin alkoxide initiators in organic media. Recently, the use of supercritical carbon dioxide as polymerization medium was proposed as a potential alternative to the use toxic organic solvents. Nevertheless, due to the non-solubility of PCL in this medium, the growing chains rapidly precipitate during their synthesis leading to the formation of a bulky material that is typical of a precipitation polymerization. This work aims at investigating the dispersion ring-opening polymerization (ROP) of ε-caprolactone in the presence of fluoropolymer-based stabilizers, that were prepared by combining the ring opening polymerization of ε-caprolactone and atom transfer radical polymerization of heptadecafluorodecylacrylate (AC8) and so, stabilizing PCL micrometric particles in supercritical carbon dioxide. In practice, the ROP of CL was initiated by dibutyltin dimethoxide in the presence of PCL-b-PAC8 diblock stabilizers of differents molecular weight and composition. After 24h at 40°C, PCL was collected as a powder that consists of small-sized microspheres. Finally, post-polymerization purification of PCL (removal of tin catalyst that may lead to toxicological problems) was demonstrated to be quite feasible by supercritical fluid extraction (SFE) leading to the preparation of PCL with low catalytic residues. The second goal of this work aims at reporting on the use of sc CO2 for the preparation of foams of poly(epsilon-caprolactone) (PCL), that could be useful in the packaging sector and/or the biomedical sector as potential scaffolds for tissue engineering but also as substitutes for polystyrene thermoformed trays. The method that consists of saturating a polymer with a compressed or supercritical fluid, such as carbon dioxide followed by depressurization and polymer expansion was investigated. Indeed, no residual product is left in the foam, no toxic gas is produced and no resort to hydrocarbon solvents is required. Moreover, CO2 is cheap, non-toxic, recyclable, non-flammable and the technology of CO2-assisted foaming can be used in either a batch mode or in a continuous mode within a high-pressure extruder. [less ▲]

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