References of "Gilbert, Bernard"
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See detailShape-memory materials based on thermoreversibly cross-linked poly-ε-caprolactones
Defize, Thomas ULg; Riva, Raphaël ULg; Thomassin, Jean-Michel ULg et al

Poster (2013, August 19)

Shape memory polymers (SMPs) are materials that are able to change their shape from a temporary shape to a permanent one by application of a stimulus such as heat or light. SMPs are usually chemically or ... [more ▼]

Shape memory polymers (SMPs) are materials that are able to change their shape from a temporary shape to a permanent one by application of a stimulus such as heat or light. SMPs are usually chemically or physically crosslinked materials that exhibit an elastomeric behaviour above a glass or melting transition temperature. Poly(ε-caprolactone) (PCL) is one of the most widely studied polymers for the development of SMPs. PCL presents several advantages such as a melting transition temperature close to human body temperature, a high biocompatibility, is (bio)degradable and potentially biosourced. So, this polymer is highly relevant for both degradable packaging and also for biomedical devices such as resorbable suture wires or stents. However, after crosslinking, the material can not be reprocessed, preventing any reuse/recycling. The main purpose of this work is to provide a solution to this major drawback, which would then enable, for example, to reshape packaging films after use or to reprocess trimmings remaining after production. Amongst current trends in the design of new polymer and composite materials, organic reactions that are able to create and reversibly disrupt chemical bonds upon an external stimulus (temperature, irradiation,…) are currently gaining more and more attention in macromolecular engineering and are used in various areas such as remendable materials, drug delivery systems, stimulus-degrading materials or recyclable materials. Amongst all the reversible links described in the literature, thermally (4+2) reversible cycloadditions present interesting properties such as the creation of robust bonds and well defined reversibility conditions. As an example, the application of furan/maleimide adducts as covalent link, which cycloreversion is largely favored in the range of temperature (90-120°C), is widely reported. This contribution aims at reporting a new concept for the preparation of well defined and recyclable PCL based reversibly cross-linked SMPs by the formation of reversible carbon-carbon bonds. For this purpose, commercially-available linear and multi-arm star shaped PCL precursors have been selected and selectively functionalized at their chain ends either by a diene (furan, anthracene) or a dienophile (maleimide). Typically, PCL-based shape memory materials have been prepared by mixing a stoichiometric amount of diene-bearing and maleimide-bearing PCLs in a twin-screw mini-extruder at a temperature which favors cycloreversion. The polymer blend is then cured at 65°C (just above PCL melting temperature), with the purpose to increase chains mobility and improve the formation of the adducts. Cross-linked PCLs were obtained, as evidenced by swelling experiments. The shape memory properties of the materials have been studied by cyclic tensile thermomechanical analysis. The influence of the architecture of the PCL precursors as well as the nature of the Diels-Alder moieties on the cross-linking rate and on the shape memory properties has been studied. Reversibility of the network formation in the case of furan, used as diene, has been assessed by rheology and by recycling experiment. [less ▲]

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See detailDevelopment of a quantitative approach to measure phospholipids in dried drops by Raman spectroscopy
Malherbe, Cédric ULg; Jadoul, Laure ULg; Gilbert, Bernard ULg et al

Poster (2013, May 24)

Phospholipids, PL, such as the phosphatidylcholine PC(18:0/18:1), play a role in the structure of living cells and are suspected to be part of the development of some diseases, for example cancers. Mass ... [more ▼]

Phospholipids, PL, such as the phosphatidylcholine PC(18:0/18:1), play a role in the structure of living cells and are suspected to be part of the development of some diseases, for example cancers. Mass spectrometry enables the structural analysis of PL in complex biological media but imaging mass spectrometry by MALDI-MS is rather limited for quantification purposes. Complementarily, Raman spectroscopy as a non invasive and non destructive method is a potential candidate to quantify and visualise the spatial distribution of the PL by molecular imaging. Unfortunately, the lack of specific chemical function in PL, compared to others biomolecules, limits the use of Raman spectroscopy in the identification process of those PL in complex biological samples. The results presented here belong to a first study of the application of the Raman analyses on dried residues of PL and mice brain tissue performed in the lab. [less ▲]

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See detailThermoreversibly cross-linked poly-ε-caprolactones for the elaboration of shape memory materials
Defize, Thomas ULg; Riva, Raphaël ULg; Thomassin, Jean-Michel ULg et al

Poster (2013, April 19)

This contribution aims at reporting a new concept for the preparation of well defined and recyclable PCL- based reversibly cross-linked shape memory polymer by the formation of reversible carbon-carbon ... [more ▼]

This contribution aims at reporting a new concept for the preparation of well defined and recyclable PCL- based reversibly cross-linked shape memory polymer by the formation of reversible carbon-carbon bonds. For this purpose, commercially-available star-shaped PCL precursors were selected and selectively modified at their chain ends either by a diene (furan) or a dienophile (maleimide). PCL-based shape memory materials were prepared by mixing a stoichiometric amount of diene-bearing and maleimide-bearing PCLs at a temperature which favors cycloreversion. The polymer blend is then cured at 65°C (slightly above PCL melting temperature), with the purpose to increase chains mobility and improve the formation of the adducts. The Diels-Alder kinetics has been followed by Raman spectroscopy and the PCL cross-linking was evidenced by both swelling experiments and rheological measurements. The obtained cross-linked PCL was characterized by shape memory properties with excellent fixity and recovery, as determined by cyclic tensile thermomechanical analysis. [less ▲]

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See detailDirect determination of the NaF/AlF3 molar ratio by raman spectroscopy in NaF-AlF3-CaF2 melts at 1000° C
Malherbe, Cédric ULg; Gilbert, Bernard ULg

in Analytical Chemistry (2013)

For the last 40 years, Raman spectroscopy has been very useful in investigating the structure of corrosive molten salts, such as the cryolite-based melts widely used as electrolyte in the Hall-Heroult ... [more ▼]

For the last 40 years, Raman spectroscopy has been very useful in investigating the structure of corrosive molten salts, such as the cryolite-based melts widely used as electrolyte in the Hall-Heroult process. Even if this process remains the most economically efficient for metallic aluminum electro-production, it suffers from a high energy loss, which is dependent on the melt composition. Therefore, controlling the chemical composition of the electrolyte is essential. The present paper proposes to apply Raman spectroscopy for the direct determination of the NaF-AlF3 molar ratio in NaF-AlF3-CaF2-based melts. Despite the experimental difficulties, a calibration curve based on equilibria taking place in the melt has been developed and the procedure has been successfully compared to industrial samples of known compositions. The possible exportation of the laboratory scale procedure to an industrial environment application for the control of the Hall-Heroult process is finally discussed. [less ▲]

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See detailRedox reactions in Prussian blue containing paint layers as a result of light exposure
Samain, Louise ULg; Gilbert, Bernard ULg; Grandjean, Fernande ULg et al

in Journal of Analytical Atomic Spectrometry [=JAAS] (2013)

Prussian blue, a mixed valence pigment, typically KFeIII[FeII(CN)6].xH2O, was the most widely used blue artistic pigment from ca. 1720 to the 1970's but, unfortunately, its paint layers, especially when ... [more ▼]

Prussian blue, a mixed valence pigment, typically KFeIII[FeII(CN)6].xH2O, was the most widely used blue artistic pigment from ca. 1720 to the 1970's but, unfortunately, its paint layers, especially when used in conjunction with a white pigment, tend to fade or turn green upon extended exposure to light. In order to identify the mechanism underlying these changes, paint layers have been prepared with differing amounts of these white pigments and subjected to accelerated light exposure fading. The resulting unfaded and faded paint layers as well as both the Berlin white pigment, Fe2II[FeII(CN)6], and the partially oxidized Berlin green pigment, {KFeIII[FeII(CN)6]}x{FeIII[FeIII(CN)6]}1–x, have been characterized by Raman and iron-57 Mössbauer spectroscopy. The results indicate that, upon fading, the Prussian blue pigment painted with a linseed oil binder and (PbCO3)2Pb(OH)2 or ZnO, and to a lesser extent with TiO2, undergoes a reduction at the exposed paint surface and an oxidation in the bulk of the paint layer. This combined reduction and oxidation disrupts, at least in part, the FeIII–N–C–FeII intervalent electron transfer pathways in Prussian blue thus leading to pigment fading through a reduction in the intervalent electron transfer absorbance at about 700 nm. [less ▲]

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See detailDevelopment of a quantitative approach to measure phospholipids in dried drops by Raman spectroscopy
Malherbe, Cédric ULg; Jadoul, Laure; Gilbert, Bernard ULg et al

Poster (2012, October)

We present here the results obtained during our tentative to analyse quantitatively dried drops of phospholipidic solutions by Raman spectroscopy. Drops of different solutions of phospholipid were deposed ... [more ▼]

We present here the results obtained during our tentative to analyse quantitatively dried drops of phospholipidic solutions by Raman spectroscopy. Drops of different solutions of phospholipid were deposed onto different material supports. The spots were then analyses by confocal Raman microspectroscopy. Experimental settings have been optimised and the analysis of the intensity profile of the Raman signal inside the spot allows the establishment of a calibration curve for the determination of the phospholipids amount within a 1 µL solution. [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 detailDetermination of the composition of cryolitic melts involved in the Hall-Heroult process by Raman spectroscopy
Malherbe, Cédric ULg; Gilbert, Bernard ULg

Conference (2012, August)

Considering our experience in the study of such highly corrosive media by Raman spectroscopy and since the bath spectrum is function of the molar NaF/AlF3 ratio and the Al2O3 content, we have proposed in ... [more ▼]

Considering our experience in the study of such highly corrosive media by Raman spectroscopy and since the bath spectrum is function of the molar NaF/AlF3 ratio and the Al2O3 content, we have proposed in the past to apply that technique to the direct determination of the melt composition . Recent instrumental developments on CCD based spectrometers have made the proposed method more feasible. This presentation will first demonstrate that, employing an updated instrument provided with new optical filters and a more sensitive CCD detector, better quality spectra are obtained. Afterward, new results relevant to the development of our analytical method for the direct determination of the molar NaF/AlF3 ratio and the Al2O3 content in cryolitic melt will be discuss. Different aspects of the calculation procedure will be illustrated:  Estimation and subtraction method of the Rayleigh decay from melt spectra;  Development of an internal normalisation procedure based on equilibria in the melt and assisted by home-made software;  Establishment of calibration curves for the determination of the molar ratio NaF/AlF3 in the melt;  Establishment of calibration curves for the determination of oxide content in the melt;  Overall procedure for the composition determination. [less ▲]

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See detailContribution to the identification of α-, β- and ε-copper phthalocyanine blue pigments in modern artists' paints by X-ray powder diffraction, attenuated total reflectance micro-fourier transform infrared spectroscopy and micro-Raman spectroscopy
Defeyt, Catherine ULg; Vandenabeele, P.; Gilbert, Bernard ULg et al

in Journal of Raman Spectroscopy (2012), 43

Since the end of the 20th century, the α-, β- and ε-copper phthalocyanine (CuPc) blue pigments are widely used in modern artists' paints. The identification of the CuPc crystalline structure can provide ... [more ▼]

Since the end of the 20th century, the α-, β- and ε-copper phthalocyanine (CuPc) blue pigments are widely used in modern artists' paints. The identification of the CuPc crystalline structure can provide useful technical and chronological information for the study of works of art. Although when a CuPc blue pigment is identified, its crystalline structure often remains unspecified despite the interest for conservation science. In this study, X-ray powder diffraction, attenuated total reflectance micro-Fourier transform infrared spectroscopy and micro-Raman spectroscopy analyses have been carried out on 15 dry pigment samples of CuPc and acrylic, vinylic, alkyd, arabic gum and oil-based artists' paints. By using the polymorphic markers underlined for dry pigments, the CuPc crystalline structure has been successfully identified for most of the analysed artists' paints. However, according to the analytical technique used and the investigated paint sample, the obtained results largely differ. © 2012 John Wiley & Sons, Ltd. [less ▲]

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See detailCharged poly(D,L-lactide) nanofibers: towards customized surface properties
Croisier, Florence ULg; Aqil, Abdelhafid ULg; Malherbe, Cédric ULg et al

in Macromolecular Symposia (2011), 309/310(1), 20-27

Surface-charged nanofibers were prepared by electrospinning technique (ESP). For this purpose, a copolymer bearing carboxylic acid functions was added to a poly(D,L-lactide) solution just before ESP ... [more ▼]

Surface-charged nanofibers were prepared by electrospinning technique (ESP). For this purpose, a copolymer bearing carboxylic acid functions was added to a poly(D,L-lactide) solution just before ESP process. In a basic medium, negative charges were therefore revealed on fiber surface. By deposition of positively charged particles or polyelectrolytes, surface properties of the fibers could be tailor-made for a specific application. This versatile method can, for example, be applied to the preparation of new biomedical scaffolds. [less ▲]

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See detailGenetically engineered polypeptides as a new tool for inorganic nano-particles separation in water based media
Vreuls, Christelle ULg; Genin, Alexis ULg; Zocchi, Germaine ULg et al

in Journal of Materials Chemistry (2011), 21

The present paper relates a method for the separation of an insoluble inorganic powder out of a mixture of several insoluble powders with different chemical compositions, using genetically engineered ... [more ▼]

The present paper relates a method for the separation of an insoluble inorganic powder out of a mixture of several insoluble powders with different chemical compositions, using genetically engineered inorganic binding peptides (GEPI). GEPI are small peptides that recognize and specifically bind an inorganic solid material. This GEPI is anchored to magnetic beads for easy recovery of the powder of interest from the mixture. [less ▲]

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See detailAbout Accessible Acidity Level in Ionic Liquids
Robert, Thierry ULg; Gilbert, Bernard ULg

Scientific conference (2011, April 27)

Detailed reference viewed: 43 (8 ULg)
See detailCaractérisation et vieillissement accéléré de pigments de bleu de Prusse synthétisés selon les méthodes de préparation anciennes et modernes
Samain, Louise ULg; Lauricella, Melina; Silversmit, Geert et al

Conference (2011, April 11)

Detailed reference viewed: 115 (15 ULg)
See detailFading of modern Prussian blue pigments in linseed oil medium
Samain, Louise ULg; Silversmit, Geert; Sanyova, Jana et al

Poster (2011, February 04)

Detailed reference viewed: 22 (6 ULg)