References of "Alexandre, Michaël"
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See detailEffect of clay modification on the mechanism of local deformations in PA6 nanocomposites
Dominkovics, Zita; Naveau, Elodie ULg; Jérôme, Christine ULg et al

in Macromolecular Materials and Engineering (2013), 298(7), 796-805

PA nanocomposites are prepared from clays organophilized with a phosphonium and an ammonium salt, and sodium montmorillonite is used as reference. The analysis of mechanical and micromechanical properties ... [more ▼]

PA nanocomposites are prepared from clays organophilized with a phosphonium and an ammonium salt, and sodium montmorillonite is used as reference. The analysis of mechanical and micromechanical properties of the composites reveal that several micromechanical deformation processes occur in the PA/MMT composites. The matrix cavitates at relatively small stress. Processes related to non-exfoliated clay structural units are initiated at larger stresses. Sound is emitted mainly by the fracture of particles, but debonding may also occur. The plastic deformation of the matrix dominates at larger stresses and deformations. The various local deformations are independent of each other and composite properties are not determined by silicate related processes but by the deformation of the matrix. [less ▲]

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See detailThe influence of foam morphology of multi-walled carbon nanotubes/poly(methyl methacrylate) nanocomposites on electrical conductivity
Tran, Minh Phuong ULg; Detrembleur, Christophe ULg; Alexandre, Michaël ULg et al

in Polymer (2013), 54(13), 3261-3270

Polymer/multi-walled carbon nanotubes (PMMA/MWNTs) nanocomposites foams are widely investigated during the last decade thanks to their potential applications as electromagnetic interferences shielding ... [more ▼]

Polymer/multi-walled carbon nanotubes (PMMA/MWNTs) nanocomposites foams are widely investigated during the last decade thanks to their potential applications as electromagnetic interferences shielding (EMI) materials. Electrical conductivity of the nanocomposite is a key parameter for these applications. In the frame of this work, we aim at establishing relationships between the foams morphology and their electrical conductivity. We therefore first design nanocomposite foams of various morphologies using supercritical carbon dioxide (scCO2) as physical foaming agent. The nanocomposites based on poly(methyl methacrylate) (PMMA) and different carbon nanotubes loadings are prepared by melt-mixing and foamed by scCO2 in various conditions of pressure, temperature and soaking time. The influence of these foaming conditions on the morphology of the foams (volume expansion, pore size, cell density, cell-wall thickness) is discussed. After measuring the electrical conductivity of the foams, we establish structure/properties relationships that are essential for further optimizations of the materials for the targeted application. [less ▲]

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See detailIntraocular lenses with functionalized surfaces by biomolecules in relation with lens epithelial cell adhesion
Huang, Yi-Shiang ULg; Alexandre, Michaël ULg; Bozukova, Dimitriya et al

Poster (2013, April 25)

A cataract is pathology opacity of the lens or capsule of the eye, causing impairment of vision or even blindness. Surgery, with lens extraction and intraocular lens implantation, is still the only ... [more ▼]

A cataract is pathology opacity of the lens or capsule of the eye, causing impairment of vision or even blindness. Surgery, with lens extraction and intraocular lens implantation, is still the only currently available treatment. The most common complication after implantation of intraocular lenses (IOLs) is the posterior capsular opacification (PCO) or secondary cataract. This is the result of lens epithelial cells (LECs) proliferation and their transition to mesenchymal cells. In 1997, a Sandwich theory was proposed to elucidate the developmental process of PCO. [1] According to this model, an IOL with higher affinity to LECs will induce a less PCO. In our research, the pHEMA (Poly(2-hydroxyethyl methacrylate)) based acrylic hydrophilic polymer is subjected to the surface modification by conjugating with the bioactive peptides. The RGD sequence, known for its excellent biocompatibility, is designed to stimulate the biointegration between the LECs and the polymer implant. [2]. From our research, The RGD peptide immobilized onto pHEMA surfaces significantly facilitates the adhesion of the porcine LEC. The peptide immobilized surface retains its biological function even after 10 times of autoclave. On the other hand, the immobilized peptide does not alter the hydrophobicity of the surface, the light transmission, as well as the cytotoxicity of the material. This functionalized biomaterial would possibly prevent the formation of PCO. [1] J Cataract Refract Surg. 1997 Dec;23(10):1539-42 [2] Trends Biotechnol. 2008 Jul;26(7):382-92 [less ▲]

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See detailEffect of silica-coated poly(butyl methacrylate)-block-poly(methyl methacrylate) double-shell particles on the mechanical properties of PMMA composites
Chakkalakal, G. L.; Alexandre, Michaël ULg; Boschetti-de-Fierro, Adriana et al

in Macromolecular Materials and Engineering (2012), 297(9), 887-893

Silica nanoparticles with average diameters of 12nm are grafted with PBMA-b-PMMA double shells through typical ATRP from a Si12-g-(PBMA)Br macroinitiator using 2-BriB as the initiator. A commercially ... [more ▼]

Silica nanoparticles with average diameters of 12nm are grafted with PBMA-b-PMMA double shells through typical ATRP from a Si12-g-(PBMA)Br macroinitiator using 2-BriB as the initiator. A commercially available PMMA homopolymer is used for the preparation of composites with unmodified, silane-modified and double-shell-modified silica particles. Good mechanical properties are obtained for silica double shell containing systems. The silica content in double shell particle systems is varied from 0 to 2.5 wt%. A significant improvement in impact properties is observed. The surface-modified silica particles are characterized by ATR-FTIR, NMR, GPC, and thermal analysis. TEM analysis is used to analyze the nature of dispersion of particles in the composites. [less ▲]

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See detailBioactive Intraocular Lens - A New Concept to Control Secondary Cataract
Huang, Yi-Shiang ULg; Alexandre, Michaël ULg; Bozukova, Dimitriya et al

Poster (2012, August 29)

A cataract is pathology opacity of the lens, causing impairment of vision or even blindness. Today, a surgery is still the only available treatment. The intraocular lens (IOL) is a polymer implant ... [more ▼]

A cataract is pathology opacity of the lens, causing impairment of vision or even blindness. Today, a surgery is still the only available treatment. The intraocular lens (IOL) is a polymer implant designed to replace the natural lens in the cataract surgery. The materials for IOL require excellent optical properties for light transmission, mechanical properties for folding injection during surgery, and biological properties for preventing body rejection. The biocompatibility - or more specified, bio-inert - seems to be the prerequisite in selecting the materials. [1] However, the bioinert materials could not satisfy the unmet need in the secondary cataract control. Posterior capsular opacification (PCO, or Secondary Cataract), characterized by a thick and cloudy layer of lens epithelial cells (LECs), is the most common postoperative complication. In 1997, a “Sandwich Theory” model was proposed to elucidate the developmental process of PCO. [2] In this model, the residual LECs between the lens capsular bag and the IOL undergo proliferation, migration, as well as transdifferentiation and finally induce PCO if the affinity to the IOL material is low. In our research, a bioactive molecule is introduced to the conventional acrylic hydrophilic polymer pHEMA(Poly(2-hydroxyethyl methacrylate)) by covalent conjugation. The RGD peptide sequence, being well-known for its tissue integration ability, is designed to stimulate the biointegration between the LECs and the IOL. [3]. Our data have shown the peptide grafted biomaterial not only exhibits similar optical and mechanical properties, but also reveals enhanced biological properties in cell adhesion and cell morphology maintenance. By means of surface functionalization of IOL to stabilize and restore LECs, the secondary cataract could be controlled in a regenerative medicine way. References [1] Dimitriya Bozukova (2010) Materials Science and Engineering R, 69: 63-83. [2] Reijo Linnola (1997) J Cataract Refract Surg., 10: 1539–42. [3] Ruoslahti E (1986) Cell, 44(4): 517-8. [less ▲]

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See detailCrosslinking of star-shape PCLs through Diels-Alder reactions for the preparation of shape memory polymers
Defize, Thomas ULg; Riva, Raphaël ULg; Thomassin, Jean-Michel ULg et al

Poster (2012, May 10)

Poly(ε-caprolactone) (PCL), a semi-crystalline polymer, is one of the most widely studied polymers for the development of shape memory materials when chemically cross-linked. PCL presents several ... [more ▼]

Poly(ε-caprolactone) (PCL), a semi-crystalline polymer, is one of the most widely studied polymers for the development of shape memory materials when chemically cross-linked. PCL presents several advantages such as a melting transition temperature close to human body temperature, a high biocompatibility and is (bio)degradable. So, this polymer is highly relevant for both biomedical devices such as stents or resorbable suture wires and also for degradable packaging. However, after cross-linking, the material can not be reprocessed, preventing any reuse/recycling of the material. One of the purposes of this work is to find a solution to this major drawback, which would then allow, for example, to reshape packaging films after use or to recycle trimmings remaining after fabrication. Amongst current trends in the design of new polymer and composite materials, the use of organic reactions that are able to create and reversibly disrupt chemical bonds upon an external stimulus (temperature, irradiation,…) is currently gaining more and more attention as it can lead to applications in various areas such as remendable materials, drug delivery systems, stimulus-degrading materials or recyclable materials. 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. Amongst all the reversible links described in the literature, thermally (4+2) reversible cycloadditions present interesting features 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. For this purpose, commercially-available star-shaped PCL precursors have been selected and selectively modified 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 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 detailSurface-initiated controlled radical polymerization from silica nanoparticles with high initiator density
Chakkalakal, G. Louis; Alexandre, Michaël ULg; Abetz, Clarissa et al

in Macromolecular Chemistry and Physics (2012), 213(5), 513-528

The surface of silica nanoparticles is modified using the “grafting from” technique. A multi-step reaction is conducted to modify their surface properties. (3-glycidoxypropyl) trimethoxysilane (GPS) is ... [more ▼]

The surface of silica nanoparticles is modified using the “grafting from” technique. A multi-step reaction is conducted to modify their surface properties. (3-glycidoxypropyl) trimethoxysilane (GPS) is used as the coupling agent for the fixation of atom transfer radical polymerization (ATRP) initiator. The grafting efficiency of GPS mixed with aqueous suspension of silica nanoparticles is studied, followed by the coupling efficiency towards ATRP initiator. The bromide concentration of ATRP initiator is kept constant for comparative kinetic studies of styrene and MMA polymerizations. The consequences at high conversions and the particle size distribution are studied. The behaviour of the glass transition temperature of either polymer-modified particles and the nature of dispersion of polymer-coated silica particles are analyzed. [less ▲]

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See detailProcess for preparing electromagnetic interference shileding materials
Thomassin, Jean-Michel ULg; Jérôme, Christine ULg; Detrembleur, Christophe ULg et al

Patent (2012)

The present invention relates to a process for preparing an electromagnetic interference shielding material, or a precursor thereof, comprising a first polymer matrix and carbon conductive loads, said ... [more ▼]

The present invention relates to a process for preparing an electromagnetic interference shielding material, or a precursor thereof, comprising a first polymer matrix and carbon conductive loads, said process comprises the steps of: (a) Forming a reaction mixture comprising carbon conductive loads and a polymerizable medium said polymerizable medium comprising one or more monomers dissolved in a solvent, (b) Exposing the reaction mixture to polymerization conditions to polymerize said polymerizable medium and thus form a polymer, and (c) Forming a precipitate or an agglomerate of an electromagnetic interference shielding material made of less than 50 wt.% carbon conductive loads dispersed in the first polymer matrix formed in step (b), characterized in that, said polymer is insoluble in said solvent and in that a fraction of the polymer chains thus formed are grafted on part of the surface of the carbon conductive loads. [less ▲]

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See detailProcess for preparing electromagnetic interference shileding materials
Thomassin, Jean-Michel ULg; Jérôme, Christine ULg; Detrembleur, Christophe ULg et al

Patent (2012)

The present invention relates to a process for preparing an electromagnetic interference shielding material, or a precursor thereof, comprising a first polymer matrix and carbon conductive loads, said ... [more ▼]

The present invention relates to a process for preparing an electromagnetic interference shielding material, or a precursor thereof, comprising a first polymer matrix and carbon conductive loads, said process comprises the steps of: (a) Forming a reaction mixture comprising carbon conductive loads and a polymerizable medium said polymerizable medium comprising one or more monomers dissolved in a solvent, (b) Exposing the reaction mixture to polymerization conditions to polymerize said polymerizable medium and thus form a polymer, and (c) Forming a precipitate or an agglomerate of an electromagnetic interference shielding material made of less than 50 wt.% carbon conductive loads dispersed in the first polymer matrix formed in step (b), characterized in that, said polymer is insoluble in said solvent and in that a fraction of the polymer chains thus formed are grafted on part of the surface of the carbon conductive loads. [less ▲]

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See detailMultifunctional poly( ε-caprolactone)-forming networks by Diels–Alder cycloaddition: effect of the adduct on the shape-memory properties
Defize, Thomas ULg; Riva, Raphaël ULg; Jérôme, Christine ULg et al

in Macromolecular Chemistry and Physics (2012), 213(2), 187-197

Star-shaped poly(e-caprolactone)s are functionalized by various dienes (furan and anthracene) and a dienophile (maleimide), and the kinetics of network formation by melt-blending is compared for both ... [more ▼]

Star-shaped poly(e-caprolactone)s are functionalized by various dienes (furan and anthracene) and a dienophile (maleimide), and the kinetics of network formation by melt-blending is compared for both Diels–Alder adducts. When curing at 60 °C, the anthracene–maleimide network forms more rapidly and gives rise to a more crosslinked material than with the furan–maleimide adduct. Shape-memory properties of the networks are compared in terms of Diels–Alder adduct stability. Both materials exhibit excellent fixity and recovery ratios, but the relatively low retro Diels–Alder temperature of the furan–maleimide adduct perturbs the mechanical stability of the network during cyclic tensile testing between 0 and 60 °C, whereas the anthracene–maleimide adduct is shown to be stable up to 150 °C. [less ▲]

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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 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 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 detailMorphology and mechanical properties of bisphenol A polycarbonate/poly(styrene-co-acrylonitrile) blends based clay nanocomposites
Lin, Demiao; Boschetti-de-Fierro, Adriana; Alexandre, Michaël ULg et al

in Composites Science & Technology (2011), 71(16), 1893-1897

Two organic modified clays (Cloisite®30B (CL30B) and PCL/Cloisite®30B masterbatch (MB30B)) were used to improve the mechanical properties of polycarbonate (PC)/poly (styrene-co-acrylonitrile) (SAN) blends ... [more ▼]

Two organic modified clays (Cloisite®30B (CL30B) and PCL/Cloisite®30B masterbatch (MB30B)) were used to improve the mechanical properties of polycarbonate (PC)/poly (styrene-co-acrylonitrile) (SAN) blends. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) measurements of the melt blended nanocomposites revealed that partially exfoliated and partially degraded structure was obtained and the clay platelets were located mostly in the SAN phase and at the two-phase boundary. Dispersion of the clay platelets is better when MB30B were used. The mechanical properties of the clays filled nanocomposites vary accordingly and when MB30B is used better mechanical properties can be achieved. Tensile strength increases 41% at maximum as the CL30B loading is 5 wt.%, while elongation at break decreases dramatically. Impact strength can be improved up to 430% compared to the pure blend when 1 wt.% MB30B was used. [less ▲]

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See detailOrganic compositions for repeatedly adjustable optical elements and such elements
Jérôme, Christine ULg; Alexandre, Michaël ULg; Jellali, Rachid ULg

Patent (2011)

The invention relates to an organic transparent liquid composition comprising preformed polymeric chains having some photoactive groups per chain that can reversibly couple, being capable in this way to ... [more ▼]

The invention relates to an organic transparent liquid composition comprising preformed polymeric chains having some photoactive groups per chain that can reversibly couple, being capable in this way to form a transparent solid polymer network with a shape that can be repeatedly and reversibly adjusted by at least local irradiation of the network with electromagnetic waves of different wave lengths whereby the liquid composition is cross-linked at at least one wave length L1 on the one hand and is liquid again by cleaving the cross-link nodes by irradiating the material at at least one other wavelength L2 on the other hand in order to repeatedly adjust the optical properties of said composition in its photo-cross linked state. The composition is applicable as a starting material for intraocular lenses and for other lenses and optical elements. [less ▲]

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See detailPMMA/ carbon nanotube nanocomposite foams for EMI shielding application
Thomassin, Jean-Michel ULg; Vuluga, Daniela; Huynen, Isabelle et al

Conference (2011, August 30)

Detailed reference viewed: 27 (5 ULg)