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See detailA convenient route for the dispersion of carbon nanotubes in polymers: Application to the preparation of electromagnetic interference (EMI) absorbers
Thomassin, Jean-Michel ULg; Vuluga, Daniela; Alexandre, Michaël ULg et al

in Polymer (2012), 53(1), 169-174

A new dispersion technique has been implemented which consists in the polymerization of a monomer in the presence of CNTs in a bad solvent of the polymer. During its formation, the polymer precipitates ... [more ▼]

A new dispersion technique has been implemented which consists in the polymerization of a monomer in the presence of CNTs in a bad solvent of the polymer. During its formation, the polymer precipitates and entraps all the CNTs. Thanks to the establishment of a suitable CNTs dispersion, this method promotes much higher electrical conductivity in the resulting nanocomposite than more conventional techniques, i.e. melt-mixing and co-precipitation. Moreover, the quantity of solvent required is much lower than in the co-precipitation method that makes this process industrially viable. One potential application of these nanocomposites has been demonstrated by the preparation of foams using the supercritical CO2 technology that present very high electromagnetic interference (EMI) absorbing properties since more than 90% of the incoming power being absorbed in the foam. [less ▲]

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See detailSynthesis of star and H-shape polymers via a combination of cobalt-mediated radical polymerization and nitrone mediated radical coupling reactions
Detrembleur, Christophe ULg; Debuigne, Antoine ULg; Altintas, Ozcan et al

in Polymer Chemistry (2012), 3(1), 135-147

Via consecutive cobalt-mediated radical polymerization (CMRP), nitrone-mediated radical coupling (NMRC) and copper catalyzed azide-alkyne cycloaddition (CuAAC), polymers with mikto-arm star and H-shape ... [more ▼]

Via consecutive cobalt-mediated radical polymerization (CMRP), nitrone-mediated radical coupling (NMRC) and copper catalyzed azide-alkyne cycloaddition (CuAAC), polymers with mikto-arm star and H-shape architecture were synthesized. Poly(vinyl acetate)40-block-poly(acrylonitrile)78-Co(acac)2 polymers were synthesized via CMRC and subsequently coupled using an alkyne functional nitrone. The coupling efficiency of the NMRC process was assessed employing N-tert-butyl a-phenyl nitrone (PBN), which is structurally very similar to the later employed coupling agent. Generally, coupling efficiencies of close to 90% or higher were observed in all cases. Since the coupling reaction yields triblock copolymers bearing an alkoxyamine functionality (and thus also an alkyne group) in the middle of the chain, well defined PEG conjugates could be obtained via CuAAC. Miktoarm star polymers of the structure (PVAc-b-PAN)2-PEG were generated as well as H-shaped material of the structure (PVAc-b-PAN)2-PEG-(PVAc-b-PAN)2 via conjugation with bifunctional PEG. In all cases, very narrow molecular weight material was obtained. Molecular weight analysis of the intermediate and the final products reveals that the hydrodynamic volume of the miktoarm star and the H-shaped materials is not substantially increased during the final conjugation reaction despite the fact that the absolute molecular weight increases by more than a factor of two in the latter case. Success of the conjugation reactions was confirmed via composition analysis via NMR. [less ▲]

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See detailMechanical testing of electrospun PCL fibers
Croisier, Florence ULg; Duwez, Anne-Sophie ULg; Jérôme, Christine ULg et al

in Acta Biomaterialia (2012), 8(1), 218-224

Poly(ε-caprolactone) (PCL) fibers ranging from 250 to 700 nm in diameter were produced by electrospinning a polymer tetrahydrofuran/N,N-dimethylformamide solution. The mechanical properties of the fibrous ... [more ▼]

Poly(ε-caprolactone) (PCL) fibers ranging from 250 to 700 nm in diameter were produced by electrospinning a polymer tetrahydrofuran/N,N-dimethylformamide solution. The mechanical properties of the fibrous scaffolds and individual fibers were measured by different methods. The Young’s moduli of the scaffolds were determined using macro-tensile testing equipment, whereas single fibers were mechanically tested using a nanoscale three-point bending method, based on atomic force microscopy and force spectroscopy analyses. The modulus obtained by tensile-testing eight different fiber scaffolds was 3.8 ± 0.8 MPa. Assuming that PCL fibers can be described by the bending model of isotropic materials, a Young’s modulus of 3.7 ± 0.7 GPa was determined for single fibers. The difference of three orders of magnitude observed in the moduli of fiber scaffolds vs. single fibers can be explained by the lacunar and random structure of the scaffolds. [less ▲]

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See detailKey role of intramolecular metal chelation and hydrogen bonding in the cobalt-mediated radical polymerization of N-vinyl amides
Debuigne, Antoine ULg; Morin, Aurélie; Kermagoret, Anthony ULg et al

in Chemistry : A European Journal (2012), 18

This work reveals the preponderance of an intramolecular metal chelation phenomenon in a controlled radical polymerization system involving the reversible trapping of the radical chains by a cobalt ... [more ▼]

This work reveals the preponderance of an intramolecular metal chelation phenomenon in a controlled radical polymerization system involving the reversible trapping of the radical chains by a cobalt complex, i.e. the bis(acetylacetonato)cobalt(II). The cobalt-mediated radical polymerization (CMRP) of a series of N-vinyl amides was considered in order to evidence the effect of the cobalt chelation by the amide moiety of the last monomer unit of the chain. The latter reinforces the cobalt-polymer bond in the order N-vinylpyrrolidone < N-vinyl caprolactam < N-methyl-N-vinyl acetamide, and is responsible for the optimal control of the polymerizations observed for the last two monomers. Such a double linkage between the controlling agent and the polymer, via a covalent bond and a dative one, is unique in the field of controlled radical polymerization and represents a powerful opportunity to fine tune the equilibrium between latent and free radicals. The possible hydrogen bond formation is also taken into account in the case of N-vinyl acetamide and N-vinyl formamide. These results are essential for understanding factors influencing a Co-C bond strength in general, and the CMRP mechanism in particular, but also for developing a powerful platform for the synthesis of new precision poly(N-vinyl amide)s, an important class of polymers which sustains numerous applications today. [less ▲]

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See detailCobalt-mediated radical polymerization
Debuigne, Antoine ULg; Jérôme, Robert ULg; Jérôme, Christine ULg et al

in Schlüter, Dieter A.; Hawker, Craig; Sakamoto, Junji (Eds.) Synthesis of polymers: new structures and methods (2012)

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See detailStructure, properties and obtention routes of flaxseed lignan secoisolariciresinol
Sainvitu, Pauline ULg; Nott, Katherine ULg; Richard, Gaetan ULg et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2012), 16(1), 115-124

Following a brief description of the structure and nomenclature of the lignan family, this review focuses on the flaxseed lignan secoisolariciresinol (SECO). The main properties, the analysis methods and ... [more ▼]

Following a brief description of the structure and nomenclature of the lignan family, this review focuses on the flaxseed lignan secoisolariciresinol (SECO). The main properties, the analysis methods and two routes for the preparation of SECO, i.e. extraction from renewable raw material and (hemi)-synthesis, are reviewed. Green methods recently developed for the first route and chemical syntheses inspired from biosyntheses for the second one are the main subjects of this paper. [less ▲]

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See detailRecent developments in ring-opening polymerization of lactones
Lecomte, Philippe ULg; Jérôme, Christine ULg

in Rieger, Bernhard; Künkel, Andreas; Coates, Geoffrey W. (Eds.) et al Synthetic Biodegradable Polymers (2012)

Polylactones are important biodegradable and biocompatible environmentally friendly polyesters widely used for many applications and more particularly for biomedical applications. This review covers ... [more ▼]

Polylactones are important biodegradable and biocompatible environmentally friendly polyesters widely used for many applications and more particularly for biomedical applications. This review covers recent advances dealing with their synthesis by ring-opening polymerization (ROP). First, lactones polymerized by ROP will be reviewed with special attention paid to the effect of the ring size on polymerizability. Aliphatic polyesters synthesized by the ROP of lactones can also be obtained by polycondensation. The advantages of ROP compared with polycondensation will be highlighted. The second section is devoted to the different mechanisms used to carry out ROP, such as anionic, coordination, cationic, enzymatic, and organocatalytic polymerization. Special attention will be paid to the control imparted to the polymerization by the use of catalysts and initiators. The polymerization of lactones substituted by functional groups will be shown to afford functionalized aliphatic polyesters. The final section will focus on the synthesis of different architectures such as star-shaped, graft, hyperbranched, and macrocyclic polylactones in the frame of macromolecular engineering. [less ▲]

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See detailSurface and bio-adhesion properties of new hydrophobic and current materials for artificial intraocular lens
Bertrand, Virginie ULg; Svaldo Lanero, Tiziana ULg; Duwez, Anne-Sophie ULg et al

Poster (2012)

A high bio-adhesion appears to be one of the key factor for posterior capsular opacification (PCO) prevention. Indeed, the proteins adsorption and the lens epithelial cells (LEC) adhesion both contribute ... [more ▼]

A high bio-adhesion appears to be one of the key factor for posterior capsular opacification (PCO) prevention. Indeed, the proteins adsorption and the lens epithelial cells (LEC) adhesion both contribute to PCO development. We present in this work the comparison of a new glistening free hydrophobic material (GF® from Physiol) with benchmark hydrophobic and hydrophilic materials regarding their chemicophysical properties and their respective ability to interact with lens epithelial cells and proteins. For this purpose, we determined the hydrophobicity by contact angle measurement (assessed by water drop and air bubble methods), the surface adhesiveness by atomic force microscopy (AFM), the proteins adsorption by fluorescent measurement and the LEC adhesion by the determination of cell density. The new hydrophobic material presents comparable hydrophobicity, proteins adsorption and LEC adhesion to current commercial hydrophobic material. Its adhesiveness, measured with the AFM, is intermediate between hydrophilic and hydrophobic materials. In conclusion, the bio-adhesion properties of this new glistening free hydrophobic IOL material are similar to generic hydrophobic acrylic materials and therefore should to the same extent prevent PCO. [less ▲]

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See detail"Click chemistry" to derived antimicrobial polymers
Lecomte, Philippe ULg; Riva, Raphaël ULg; Jérôme, Christine ULg

in Lagaron, José Maria; Ocio Zapata, Maria José; Lopez-Rubio, Amparo (Eds.) Antimicrobial polymers (2012)

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See detailChitosan-based biomimetic scaffolds and methods for preparing the same
Filée, Patrick; Freichels, Astrid ULg; Jérôme, Christine ULg et al

Patent (2011)

The invention concerns chitosan-based biomimetic scaffolds and methods for modulating their intrinsic properties such as rigidity, elasticity, resistance to mechanical stress, porosity, biodegradation and ... [more ▼]

The invention concerns chitosan-based biomimetic scaffolds and methods for modulating their intrinsic properties such as rigidity, elasticity, resistance to mechanical stress, porosity, biodegradation and absorbance of exudates. Therefore, the present invention relates to a layered chitosan-based scaffold wherein said layered scaffold comprises at least two fused layers, wherein at least one layer consists of a chitosan nanofiber scaffold membrane and at least one of the other layers of a porous chitosan scaffold support layer. Moreover, the present invention provides a layered chitosan-based scaffold characterized by (i) a good adhesion between the porous and nanofiber layers, (ii) a tuneable porosity of the nanofiber layer by tuning the distance between the nanofibers, (iii) a stable nanofibers and porous morphology even when immersed in water or other solvents and a process for the preparation of such layered chitosan-based scaffold.Finally, the present invention provides the use of the layered electrospun chitosan-based scaffold of the invention or the layered electrospun chitosan-based scaffold produced by the process of the invention as a wound dressing, in tissue engineering or for biomedical applications. [less ▲]

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See detailChitosan-based biomimetic scaffolds and methods for preparing the same
Filée, Patrice; Freichels, Astrid ULg; Jérôme, Christine ULg et al

Patent (2011)

The invention concerns chitosan biomimetic scaffolds and methods for modulating their intrinsic properties such as rigidity, elasticity, resistance to mechanical stress, porosity, biodegradation and ... [more ▼]

The invention concerns chitosan biomimetic scaffolds and methods for modulating their intrinsic properties such as rigidity, elasticity, resistance to mechanical stress, porosity, biodegradation and absorbance of exudates. Therefore, the present invention relates to a layered chitosan scaffold wherein said layered scaffold comprises at least two fused layers, wherein at least one of the fused layers comprises a chitosan nanofiber membrane and the other fused layer comprises a porous chitosan support layer. Moreover, the present invention provides a layered chitosan scaffold characterized by (i) a good adhesion between the porous and nanofiber layers, (ii) a tuneable porosity of the nanofiber layer by tuning the distance between the nanofibers, (iii) a stable nanofibers and porous morphology even when immersed in water or other solvents and a process for the preparation of such layered chitosan scaffold. Finally, the present invention provides the use of the layered electrospun chitosan scaffold of the invention or the layered electrospun chitosan scaffold produced by the process of the invention as a wound dressing, in tissue engineering or for biomedical applications. [less ▲]

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See detailDesign of reversibly disulfide core cross-linked polymer micelles
Cajot, Sébastien ULg; Schol, Daureen ULg; Danhier, F. et al

Poster (2011, December 07)

Detailed reference viewed: 31 (10 ULg)
See detailNew glucose-responsive polyelectrolyte microcapsules
Alaimo, David ULg; Detrembleur, Christophe ULg; Auzély-Velty, Rachel et al

Poster (2011, December 06)

Diabetes is a disorder of glucose regulation, characterized by an accumulation of glucose in the blood. The breakdown of glucose regulation can be attributed to the pancreas’s inability to secrete insulin ... [more ▼]

Diabetes is a disorder of glucose regulation, characterized by an accumulation of glucose in the blood. The breakdown of glucose regulation can be attributed to the pancreas’s inability to secrete insulin or to the body’s inability to properly use it. The usual treatment for type 1 diabetes consists in multiple subcutaneous insulin injections, daily administered using needles, insulin pen or insulin pump. However, this method doesn’t maintain normoglycemia and can lead to complications such as limb amputation, blindness, and kidney failure. To avoid such abnormal episodes, scientists imagined smart systems which are able to regulate the glucose level by themselves. During the past decades, a large variety of micro- and nanocarriers have been developed in order to improve efficiency, availability and toxicity profiles of drugs. In this field, stimuli-responsive polymer multilayers have attracted great scientific interest because of their potential applications as controlled delivery or release systems, for chemicals and drugs. A category of stimuli-responsive materials is able to sense glucose and respond to it by a modification of their porosity, leading to a release of insulin. The objective of this work was to investigate the formation of glucose responsive hollow microcapsules (5 microns) made of polyelectrolyte copolymers. These copolymers are composed of carbohydrate-sensitive functions, such as boronic acid and diols (PVOH), known for forming reversible covalent ether bond. In presence of carbohydrates such as glucose, the ether bonds will be reversibly broken and, consequently, the porosity of the glucose particles will change. Therefore, polyelectrolyte copolymers were synthesized by control radical polymerization, i.e. reversible addition-fragmentation chain transfer (RAFT, polyboronic acid) and cobalt-mediated radical polymerization (CMRP, PVOH). Using these polyelectrolytes as polyanions and poly(allylamine) (PAH) as a polycation, we undertook the formation of layer-by-layer capsules starting with a template of CaCO3microparticles which can be dissolved with EDTA leading to the formation of hollow microcapsules. Bovin serum albumin isothiocyanate (BSA-FITC) was used to fill the CaCO3microparticles and to determine the porosity of the resulting capsules in function of the glucose concentration. The sugar-dependent porosity is investigated by following the release of encapsulated BSA-FITC by spectro-fluoroscopy. [less ▲]

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See detailThermo-reversible reactions for the preparation of smart materials: recyclable covalently-crosslinked shape memory polymers
Defize, Thomas ULg; Riva, Raphaël ULg; Thomassin, Jean-Michel ULg et al

in Macromolecular Symposia (2011), 309/310(1), 154-161

[4+2] thermoreversible Diels-Alder cycloaddition has been used to crosslink star-shaped poly(ε-caprolactone) in order to produce networks based on strong carbon-carbon covalent bondings. Depending on the ... [more ▼]

[4+2] thermoreversible Diels-Alder cycloaddition has been used to crosslink star-shaped poly(ε-caprolactone) in order to produce networks based on strong carbon-carbon covalent bondings. Depending on the nature of the Diels-Alder reactants, these bonds can be thermoreversibly broken, allowing re-processing of the polymer matrix. [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 detailNovel amphiphilic mikto-arm star-shaped copolymers for the preparation of PLA-based nanocarriers
Cajot, Sébastien ULg; Riva, Raphaël ULg; Billiet, Leen et al

in Macromolecular Symposia (2011), 309/310(1), 111-122

Three-arm (A2B) and four-arm (A2B2) star-shaped copolymers based on biocompatible and biodegradable hydrophobic poly(ε-caprolactone) (PCL) (A arms) and biocompatible and bioeliminable hydrophilic poly ... [more ▼]

Three-arm (A2B) and four-arm (A2B2) star-shaped copolymers based on biocompatible and biodegradable hydrophobic poly(ε-caprolactone) (PCL) (A arms) and biocompatible and bioeliminable hydrophilic poly(ethylene oxide) (PEO) (B arms) were synthesized by the coupling of an ω-azide terminated PEO chains with PCL chain bearing one (A2B) or two (A2B2) alkyne functions at the middle of the chain by the copper mediated azide-alkyne cycloaddition (CuAAC). The amphiphilic behavior of these different stars was confirmed by micellization experiments in water followed by dynamic light scattering and transmission electron microscopy analyses. The efficiency to stabilize PLA nanoparticles was investigated in function of the stars structure. [less ▲]

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See detailChitosan-based nanofibers with multilayered structure for wound healing application
Croisier, Florence ULg; Detrembleur, Christophe ULg; Jérôme, Christine ULg

Poster (2011, November 21)

Chitosan is a natural polymer that intrinsically presents haemostatic, mucoadhesive, antimicrobial and immunostimulant properties. This polysaccharide has shown a great potential for biomedical ... [more ▼]

Chitosan is a natural polymer that intrinsically presents haemostatic, mucoadhesive, antimicrobial and immunostimulant properties. This polysaccharide has shown a great potential for biomedical applications, on account of its remarkable compatibility with physiological medium and its biodegradability. In this respect, nanometric fibers are highly interesting as their assembly mimics the skin extracellular matrix structure. Such nanofibrous materials can be prepared by electrospinning (ESP) and can be used as scaffolds, a.o. to form a temporary, artificial extracellular matrix. In the present study, electrospinning technique was combined with layer-by-layer deposition method (LBL) – a well-known method for surface coating, based on electrostatic interactions – in order to prepare multilayered chitosan-based nanofibers for wound healing application. [less ▲]

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See detailStabilization of gold nanoparticles by thermo-responsive poly (vinyl alcohol)-b-poly (N-vinylcaprolactam) copolymers
Liu, Ji ULg; Hurtgen, Marie ULg; Detrembleur, Christophe ULg et al

Poster (2011, November 21)

Stimuli-responsive nano-materials have been playing increasingly important roles in the biomedical field due to their ability to alter the physico-chemical properties in response to external stimuli, such ... [more ▼]

Stimuli-responsive nano-materials have been playing increasingly important roles in the biomedical field due to their ability to alter the physico-chemical properties in response to external stimuli, such as temperature, pH, ionic strength, magnetic field, etc. Nanohybrids bearing an inorganic core and thermo-responsive polymer shell are particularly applicable in target delivery and controlled drug release. Poly (N-vinylcaprolactam) (PNVCL) and its copolymers, exhibiting lower critical solution temperature (LCST) where the transition between hydrophilic and hydrophobic state happens, is one of the optimal choices for this core/shell structure. Here we present the in-situ fabrication of thermo-responsive gold nanohybrids coated with a novel poly(vinyl alcohol)-b-poly(N-vinylcaprolactam) (PVOH-b-PNVCL) block copolymer prepared by the cobalt-mediated radical polymerization (CMRP). The interaction between both PVOH and PNVCL segments and gold nanoparticles was confirmed by FT-IR spectra. A sharp thermo-induced phase transition with a good reversibility upon change in temperature was detected by DLS and UV/vis spectrometer. Furthermore, the presence of hydrophilic PVOH moieties endows the gold nanohybrids with improved colloidal stability above LCST without any flocculation detected, compared with the gold nanoparticles stabilized with PNVCL homopolymer. This kind of gold nanohybrids can be envisaged as a new drug delivery vehicle. [less ▲]

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See detailDesign of reversibly disulfide core cross-linked polymer micelles
Cajot, Sébastien ULg; Schol, Daureen ULg; Danhier, F. et al

Poster (2011, November 21)

Over the last decade, polymer micelles attracted an increasing interest in drug pharmaceutical research because they could be used as efficient drug delivery systems. Micelles of amphiphilic block ... [more ▼]

Over the last decade, polymer micelles attracted an increasing interest in drug pharmaceutical research because they could be used as efficient drug delivery systems. Micelles of amphiphilic block copolymers are supramolecular core-shell type assemblies of tens of nanometers in diameter. An accumulation of polymer nanocarriers to solid tumours is possible due to the EPR effect. Even if micelles get a high stability in aqueous media, the dissociation of micelles is not always preserved when they are injected in the blood compartment. This work aims at reporting on the design of reversibly cross-linked micelles based on PEO-b-PCL copolymers by introducing disulfide bridges in the micelle core to provide higher stability. Different kinds of macromolecular architectures are employed to study their impact on the micelles and their biological behavior. These new functional copolymers were all successfully micellized, reversibly cross-linked and are stealthy, which show the efficiency of the developed cross-linking process and offer a set of nanocarriers to be tested further, as shown on the first biological tests. [less ▲]

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