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See detailFrom polyester grafting onto POSS nanocage by ring-opening polymerization to high performance polyester/POSS nanocomposites
Goffin, Anne-Lise; Duquesne, Emmanuel; Raquez, Jean-Marie et al

in Journal of Materials Chemistry (2010), 20

Polyester-grafted polyhedral oligomeric silsesquioxane (POSS) nanohybrids selectively produced by ring-opening polymerization of epsilon-caprolactone and L,L-lactide (A.-L. Goffin, E. Duquesne, S. Moins ... [more ▼]

Polyester-grafted polyhedral oligomeric silsesquioxane (POSS) nanohybrids selectively produced by ring-opening polymerization of epsilon-caprolactone and L,L-lactide (A.-L. Goffin, E. Duquesne, S. Moins, M. Alexandre, Ph. Dubois, Eur. Polym. Journal, 2007, 43, 4103) were studied as ‘‘masterbatches’’ by melt-blending within their corresponding commercial polymeric matrices, i.e., poly(epsilon-caprolactone) (PCL) and poly(L,L-lactide) (PLA). For the sake of comparison, neat POSS nanoparticles were also dispersed in PCL and PLA. The objective was to prepare aliphatic polyester-based nanocomposites with enhanced crystallization behavior, and therefore, enhanced thermo-mechanical properties. Wide-angle X-ray scattering and transmission electron microscopy attested for the dispersion of individualized POSS nanoparticles in the resulting nanocomposite materials only when the polyester-grafted POSS nanohybrid was used as a masterbatch. The large impact of such finely dispersed (grafted) nanoparticles on the crystallization behavior for the corresponding polyester matrices was noticed, as evidenced by differential scanning calorimetry analysis. Indeed, well-dispersed POSS nanoparticles acted as efficient nucleating sites, significantly increasing the crystallinity degree of both PCL and PLA matrices. As a result, a positive impact on thermo-mechanical properties was highlighted by dynamic mechanical thermal analysis. [less ▲]

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See detailEffect of filler content and size on transport properties of water vapour in PLA/calcium sulfate composites
Gorrasi, Giuliana; Vittoria, Vittoria; Murariu, Marius et al

in Biomacromolecules (2008), 9

Starting from calcium sulfate (gypsum) as fermentation byproduct of lactic acid production process, high performance composites have been produced by melt-blending polylactide (PLA) and -anhydrite II (AII ... [more ▼]

Starting from calcium sulfate (gypsum) as fermentation byproduct of lactic acid production process, high performance composites have been produced by melt-blending polylactide (PLA) and -anhydrite II (AII) filler, i.e., calcium sulfate hemihydrate previously dried at 500 °C. Characterized by attractive properties due to good filler dispersion throughout the polyester matrix and favorable interactions between components, these composites are interesting for potential use as biodegradable rigid packaging. The effect of filler content and mean particle diameter on the barrier properties such as sorption and diffusion to water vapor has been examined and compared to unfilled PLA. Even without additional treatments, the presence of the filler introduced constraints on molecular mobility in the permeable phase of amorphous PLA and the amount of solvent absorbed appears lower in the highly filled composites. Surprisingly, for PLA-30% AII compositions, by addition of filler characterized by high mean particle diameter (e.g., 43 μm) the thermodynamic diffusion parameter, D0, decreased up to 2 orders of magnitude. The dimension of filler particles and their percentage in the continuous polymeric phase seem to be the most important parameters that determine the barrier properties of the PLA-AII composites to water vapor. [less ▲]

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See detailMicroscopic morphology of chlorinated polyethylene nanocomposites synthesized from poly(e-caprolactone)/clay masterbatches
Brocorens, Patrick; Benali, Samira; Broekaert, Cedric et al

in Langmuir (2008), 24

Chlorinated polyethylene (CPE) nanocomposites were synthesized by melt blending clay-rich/poly( -caprolactone) (PCL) masterbatches to CPE matrices. The masterbatches were prepared following two synthetic ... [more ▼]

Chlorinated polyethylene (CPE) nanocomposites were synthesized by melt blending clay-rich/poly( -caprolactone) (PCL) masterbatches to CPE matrices. The masterbatches were prepared following two synthetic routes: either PCL is melt-blended to the clay or it is grafted to the clay platelets by in situ polymerization. The microscopic morphology of the nanocomposites was characterized by X-ray diffraction, atomic force microscopy, transmission electron microscopy, and modulated temperature differential scanning calorimetry. When using free PCL, intercalated composites are formed, with clay aggregates that can have micrometric dimensions and a morphology similar to that of the talc particles used as fillers in commercial CPE. PCL crystallizes as long lamellae dispersed in the polymer matrix. When using grafted PCL, the nanocomposite is intercalated/exfoliated, and the clay stacks are small and homogeneously dispersed. PCL crystallizes as lamellae and smaller crystals, which are localized along the clay layers. Thanks to the grafting of PCL to the clay platelets, these crystalline domains are thought to form a network with the clay sheets, which is responsible for the large improvement of the mechanical properties of these materials. [less ▲]

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See detailCopolymerization of vinyl acetate with 1-octene and ethylene by cobalt-mediated radical polymerization
Bryaskova, Rayna ULg; Willet, Nicolas ULg; Degée, Philippe et al

in Journal of Polymer Science. Part A, Polymer Chemistry (2007), 45(12), 2532-2542

The cobalt-mediated radical polymerization of vinyl acetate was extended to copolymerization with I-alkenes (ethylene or 1-octene). In agreement with the low amount of I-alkene that could be incorporated ... [more ▼]

The cobalt-mediated radical polymerization of vinyl acetate was extended to copolymerization with I-alkenes (ethylene or 1-octene). In agreement with the low amount of I-alkene that could be incorporated into the copolymer, a gradient structure was predictable, but a. rather low polydispersity was observed. A poly(vinyl acetate)-b-poly(octene) copolymer was also successfully synthesized, leading to a poly (vinyl alcohol)-b-poly(octene) amphiphilic copolymer upon the methanolysis of the poly (vinyl acetate) block. [less ▲]

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See detailLevels and effects of PCDD/Fs and co-PCBs in sediments, mussels, and sea stars of the intertidal zone in the southern North Sea and the English Channel.
Danis, Bruno; Debacker, Virginie ULg; Trujilo Miranda, Carmen et al

in Ecotoxicology & Environmental Safety (2006), 65(2), 188-200

There is considerable concern regarding dioxin-like compounds (DLCs) in the marine environment. These ubiquitous contaminants are highly resistant to degradation, highly accumulated by marine organisms ... [more ▼]

There is considerable concern regarding dioxin-like compounds (DLCs) in the marine environment. These ubiquitous contaminants are highly resistant to degradation, highly accumulated by marine organisms, and extremely toxic. Concentrations of DLCs, including 7 polychlorodibenzo-p-dioxins, 10 polychlorodibenzofurans, and 4 coplanar polychlorinated biphenyls, were determined in sediments, mussels (Mytilus edulis), and sea stars (Asterias rubens) from five intertidal stations distributed along the Belgian coast and the English Channel. The induction of a biomarker, cytochrome P450 immunopositive protein (CYP1A IPP), was also measured in sea star pyloric caeca. Although no significant differences were found between the considered stations, DLC levels were found to be relatively high in biota, especially when the toxicity of these compounds is considered. Particular concern arises from TEQ values determined in mussels from all locations. Sea stars were found to be more discriminant between the stations. CYP1A IPP induction was found to be significantly related to DLC levels measured in sea stars and allowed significant discrimination between the considered stations. (c) 2005 Elsevier Inc. All rights reserved. [less ▲]

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See detailControlled synthesis and interface properties of new amphiphilic PCL-g-PEO copolymers
Rieger, Jutta ULg; Dubois, Philippe ULg; Jérôme, Robert ULg et al

in Langmuir (2006), 22(18), 7471-7479

Novel biodegradable and biocompatible poly(epsilon-caprolactone)-graft-poly(ethylene oxide), PCL-g-PEO, copolymers consisting of biocompatible blocks have been synthesized by ring-opening copolymerization ... [more ▼]

Novel biodegradable and biocompatible poly(epsilon-caprolactone)-graft-poly(ethylene oxide), PCL-g-PEO, copolymers consisting of biocompatible blocks have been synthesized by ring-opening copolymerization of epsilon-caprolactone (epsilon CL) and a poly(ethylene oxide) (PEO) macromonomer, i.e., PEO end-capped by an epsilon-caprolactone unit (gamma PEO.CL). The control is effective on the composition and length of both the hydrophobic polyester backbone and the hydrophilic PEO grafts. The reactivity ratios have been determined by monitoring the copolymer composition in relation to the comonomer conversion. The PCL-g-PEO copolymers have a tapered (gradient) rather than a random structure consistent with r(epsilon)CL = 3.95 and r(gamma)PEO.CL = 0.05. The amphiphilic graft copolymers display surfactant properties similar to those of PEO-b-PCL diblock copolymers of comparable composition and solubility, as supported by CHCl3/water interfacial tension measured by the pendant drop method. [less ▲]

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See detailInfluence of DNA condensation state on transfection efficiency in DNA/polymer complexes: An AFM and DLS comparative study
Volcke, C.; Pirotton, S.; Grandfils, Christian ULg et al

in Journal of Biotechnology (2006), 125(1), 11-21

Atomic force microscopy (AFM) is used to describe the formation process of polymer/DNA complexes. Two main objectives of this research are presented. The first one is to apply AFM as an effective tool to ... [more ▼]

Atomic force microscopy (AFM) is used to describe the formation process of polymer/DNA complexes. Two main objectives of this research are presented. The first one is to apply AFM as an effective tool to analyse DNA molecules and different polycation/DNA complexes in order to evaluate their degree of condensation (size and shape). The other one is to search for a relationship between the condensation state of DNA and its transfection efficiency. In this study, linear methacrylate based polymers and globular SuperFect polymers are used in order to induce DNA condensation. Ternary complexes, composed of methacrylate based polymers and polyethylene glycol (PEG)-based copolymers, are also investigated. AFM allows us to confirm good condensation conditions and relate them (or not) to transfection efficiencies. These AFM results (obtained after drying in air) are compared with measurements deduced from Dynamic Light Scattering (DLS) experiments performed in water. This comparison allowed us to identify the structural modifications resulting from deposition on the mica surface. (c) 2006 Elsevier B.V. All rights reserved. [less ▲]

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See detailControlled synthesis of an ABC miktoarm star-shaped copolymer by sequential ring-opening polymerization of ethylene oxide, benzyl beta-malolactonate, and epsilon-caprolactone
Rieger, Jutta ULg; Coulembier, Olivier; Dubois, Philippe ULg et al

in Macromolecules (2005), 38(26), 10650-10657

This paper reports on the synthesis of an amphiphilic miktoarm ABC star-shaped copolymer, s[(PEO)(PMLABz)(PCL)], consisting of biocompatible/bioresorbable arms. Indeed, PEO is a hydrophilic biocompatible ... [more ▼]

This paper reports on the synthesis of an amphiphilic miktoarm ABC star-shaped copolymer, s[(PEO)(PMLABz)(PCL)], consisting of biocompatible/bioresorbable arms. Indeed, PEO is a hydrophilic biocompatible poly(ethylene oxide) arm, PMLABz is a poly(benzyl beta-malolactonate) arm precursor of a pH-sensitive bioresorbable poly(beta-malic acid) block, and PCL is a hydrophobic bioresorbable poly(epsilon-caprolactone) arm. Each constitutive arm was prepared by ring-opening polymerization. A double-headed PEO macroinitiator [PEO-(OH)-COO-K+] was first prepared by selective hydrolysis of the alpha-lactone (2-oxepanone) end group of PEO chains end-capped by a omega-methoxy group. The anionic polymerization of benzyl beta-malolactonate (MLABz) was selectively initiated by the alpha-potassium carboxylate end group of PEO in the presence of 18-crown-6 ether. The polymerization of epsilon-caprolactone (epsilon-CL) was initiated by the hydroxyl group left at the junction of the two blocks of the as-prepared PEO-b-PMLABz diblock copolymer, in the presence of tin(II) bis(2-ethylhexanoate) (Sn(Oct)(2)). The macroinitiator, the intermediate diblock, and the final miktoarm. star-shaped copolymer were analyzed by H-1 NMR spectroscopy and size exclusion chromatography. [less ▲]

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See detailPoly(ethylene-co-vinyl acetate)/clay nanocomposites: Effect of clay nature and organic modifiers on morphology, mechanical and thermal properties
Peeterbroeck, Sophie; Alexandre, Michaël ULg; Jérôme, Robert ULg et al

in Polymer Degradation & Stability (2005), 90(2), 288-294

Nanocomposites based on an ethylene vinyl acetate copolymer (27 wt% vinyl acetate) and various (organo-modified) clays have been prepared by melt blending and their morphology, tensile and thermal ... [more ▼]

Nanocomposites based on an ethylene vinyl acetate copolymer (27 wt% vinyl acetate) and various (organo-modified) clays have been prepared by melt blending and their morphology, tensile and thermal degradation properties have been evaluated. Special attention has been paid to the influence of the clay nature and origin (montmorillonite or fluoromica) as well as on the nature of the ammonium cation organic modifier. It has been shown that nanostructure and tensile properties mainly depend on the nature of the organic modifier while the delay in thermal volatilisation of EVA during thermo-oxidation is mainly driven by the nature of the clay (mainly its aspect ratio), with no significant influence of the nanostructure of the nature of the organic modifier. (c) 2005 Elsevier Ltd. All rights reserved. [less ▲]

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See detailPolymer layered silicate/carbon nanotube nanocomposites : Morphological and rheological properties
Peeterbroeck, Sophie; Alexandre, Michaël ULg; Nagy, Janos B et al

in Macromolecular Symposia (2005), 221

Morphological and rheological properties of new ternary nanocomposites based on ethylene vinyl acetate copolymers (EVA), commercial organo-modified clays (organoclays) and purified multi-walled carbon ... [more ▼]

Morphological and rheological properties of new ternary nanocomposites based on ethylene vinyl acetate copolymers (EVA), commercial organo-modified clays (organoclays) and purified multi-walled carbon nanotubes (MWNTs), prepared via direct melt blending, have been evaluated. For sake of comparison, the corresponding binary compositions, i.e., EVA filled with either organoclays or MWNTs, have been investigated as well. While extensive exfoliation can be observed for binary EVA/clay nanocomposites, the addition of MWNTs appears to limit clay exfoliation. Rheological properties show that both clay and MWNTs increase the elastic modulus of the nanocomposites, reflecting the high degree of nanoparticle interconnectivity that can be found in these materials. [less ▲]

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See detailEnhancement of transfection efficiency through rapid and noncovalent post-PEGylation of poly(dimethylaminoethyl methacrylate)/DNA complexes
Pirotton, S.; Muller, Caroline; Pantoustier, N. et al

in Pharmaceutical Research (2004), 21(8), 1471-1479

Purpose. The aim of this work was to develop a new strategy to introduce poly(ethylene glycol) (PEG) into methacrylate-based polymer/ DNA complexes in order to produce hemocompatible particles able to ... [more ▼]

Purpose. The aim of this work was to develop a new strategy to introduce poly(ethylene glycol) (PEG) into methacrylate-based polymer/ DNA complexes in order to produce hemocompatible particles able to transfect cells in the presence of serum. Methods. Atom transfer radical polymerization was used to synthesize a well-defined poly(2-(dimethylamino) ethyl methacrylate) homopolymer ( PDMAEMA) and a poly( 2-( dimethylamino) ethyl methacrylate-b-poly( ethylene glycol) alpha-methyl ether, omega-methacrylate) palm-tree-like copolymer (P(DMAEMA-b-MAPEG)). The complexes obtained by self assembly of the pCMVbeta plasmid and the polymers were used to transfect Cos-7 cells. Their physical properties - particle size and zeta potential - were characterized respectively by dynamic light scattering and electrophoretic mobility measurements. Ex vivo hemocompatibility was also determined. Results. The PDMAEMA/pCMVbeta complexes transfected Cos-7 cells exclusively in the absence of serum. Although the P(DMAEMA-b-MAPEG) copolymer had no transfection activity per se, the addition of the latter to pre-formed PDMAEMA/DNA complexes significantly enhanced the activity and allowed transfection even in the presence of serum. The presence of palm-tree - like copolymers also improved the hemocompatibility properties of the complexes. No effect on platelet counts was observed for P(DMAEMA-b-MAPEG)/ pCMVbeta complexes, whereas a decrease of platelets was clearly observed when blood cells were incubated with PDMAEMA/pCMVbeta complexes. Conclusions. Such a synergistic effect of noncovalent PEGylation of poly( amino methacrylate)/ DNA complexes allows a new and versatile approach to tune up transfection efficiency. [less ▲]

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See detailPolymerization of epsilon-caprolactone initiated by Y alkoxide grafted onto porous silica
Martin, Eric; Dubois, Philippe ULg; Jérôme, Robert ULg

in Macromolecules (2003), 36(19), 7094-7099

Ring-opening polymerization of c-caprolactone has been initiated by Y isopropoxide grafted onto silica, in the presence of 2-propanol, in toluene at 40degreesC. The degree of polymerization is controlled ... [more ▼]

Ring-opening polymerization of c-caprolactone has been initiated by Y isopropoxide grafted onto silica, in the presence of 2-propanol, in toluene at 40degreesC. The degree of polymerization is controlled by the initial monomer/(alcohol + alkoxide) molar ratio. Deactivation of the chains by an alcohol is essential for them to be detached from the support and to be collected totally free of metal and silica residues. The alkoxide is also regenerated at the surface of the support, which allows for recycling the catalyst. [less ▲]

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See detailIn situ formation of yttrium alkoxides: A versatile and efficient catalyst for the ROP of epsilon-caprolactone
Martin, Eric; Dubois, Philippe ULg; Jérôme, Robert ULg

in Macromolecules (2003), 38(16), 5934-5941

[Tris(hexamethyldisilyl)amide] yttrium is a catalyst for the controlled ring-opening polymerization of epsilon-caprolactone when reacted with an excess of alcohol. Up to an alcohol-to-yttrium molar ratio ... [more ▼]

[Tris(hexamethyldisilyl)amide] yttrium is a catalyst for the controlled ring-opening polymerization of epsilon-caprolactone when reacted with an excess of alcohol. Up to an alcohol-to-yttrium molar ratio of 50, the chain transfer to the alcohol is quantitative, and the molecular weight of the chains can be predicted from the monomer-to-alcohol molar ratio. At alcohol-to-yttrium ratios higher than 100, the alcohol is quantitatively consumed provided that 1,1,1,3,3,3-hexamethyldisilazane, which is formed as a byproduct, is removed from the reation medium. Depending on the structure of the alcohol, end-functional polyesters can be prepared (e.g., with N-pyrrolyl and 3-thienyl end groups). Well-defined block and random copolymers of epsilon-CL with lactides and gamma-bromo-epsilon-caprolactone, respectively, have also been synthesized. Compared to aluminum alkoxides, the in situ formed yttrium alkoxides have the advantage of a much faster polymerization kinetics while preserving control. [less ▲]

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See detailExfoliated polylactide/clay nanocomposites by in-situ coordination-insertion polymerization
Paul, Marie-Amélie; Alexandre, Michaël ULg; Degée, Philippe et al

in Macromolecular Rapid Communications (2003), 24(9), 561-566

Poly(L-lactide)/layered aluminosilicate nanocomposites were synthesized in bulk by ring-opening polymerization in the presence of two organo-modified montmorillonites. When the organo-modifier consisted ... [more ▼]

Poly(L-lactide)/layered aluminosilicate nanocomposites were synthesized in bulk by ring-opening polymerization in the presence of two organo-modified montmorillonites. When the organo-modifier consisted of an ammonium cation bearing primary hydroxyl groups, polymerization was initiated by the alcohol functions after adequate activation. The growing polymer chains were directly "grafted" onto the clay surface through the hydroxyl-functionalized ammonium cations yielding exfoliated nano-composites with enhanced thermal stability. [less ▲]

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See detailHydrolytic and thermal degradation of random copolyesters of epsilon-caprolactone and 2-oxepane-1,5-dione
Dwan'Isa Latere, Jean-Pierre; Lecomte, Philippe ULg; Dubois, Philippe ULg et al

in Macromolecular Chemistry and Physics (2003), 204(9), 1191-1201

The hydrolytic and thermal stability of random copolyesters of epsilon-caprolactone (epsilon-CL) and ca. 30 mol-% 2-oxepane-1,5-dione (OPD) have been investigated. Compared with poly(epsilon-caprolactone ... [more ▼]

The hydrolytic and thermal stability of random copolyesters of epsilon-caprolactone (epsilon-CL) and ca. 30 mol-% 2-oxepane-1,5-dione (OPD) have been investigated. Compared with poly(epsilon-caprolactone) (PCL) of a comparable molecular weight, the hydrolytic degradation of the copolyester is faster in a phosphate buffer (pH = 7.4) at 37°C as confirmed by the time dependence of water absorption, weight loss, melting temperature, and molecular weight. This difference is a result of the higher hydrophilicity imparted to the copolyester by the ketone of the OPD units. The thermal degradation has been studied by thermogravimetric analysis (TGA), (HNMR)-H-1 spectroscopy, and size exclusion chromatography (SEC). The activation energy of the thermal degradation under nitrogen has been found to be lower for the copolyesters than for PCL, which indicates that the OPD co-units have a deleterious effect on the thermal stability of PCL. The thermal degradation primarily occurs by pyrolysis of the ester functions. [less ▲]

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See detailSynthesis and characterization of random copolyesters of epsilon-caprolactone and 2-oxepane-1,5-dione
Latere Dwan'Isa, Jean-Pierre; Lecomte, Philippe ULg; Dubois, Philippe ULg et al

in Macromolecules (2003), 36(8), 2609-2615

2-Oxepane-1,5-dione (OPD) has been synthesized by the Baeyer-Villiger oxidation of 1,4-cyclohexanedione and copolymerized with epsilon-caprolactone. This random copolymerization has been initiated by ... [more ▼]

2-Oxepane-1,5-dione (OPD) has been synthesized by the Baeyer-Villiger oxidation of 1,4-cyclohexanedione and copolymerized with epsilon-caprolactone. This random copolymerization has been initiated by different metal derivatives, i.e., tin octanoate, dibutyltin dimethoxide, and aluminum isopropoxide. Dibutyltin dimethoxide is the preferred initiator, and the course of polymerization is controlled by the competition of the ketone of OPD and the ester of the lactones for coordination to the initiator. Semicrystalline copolymers are formed, whose the randomness has been confirmed by DSC, H-1 NMR, and C-13 NMR analysis. A single melting temperature (Tm) has been observed, which varies regularly and monotonically with the OPD content as result of a cocrystallization phenomenom. The single glass transition temperature (Tg) obeys the Fox equation. [less ▲]

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See detailPolymerization-filled composites and nanocomposites by coordination catalysis
Dubois, Philippe ULg; Alexandre, Michaël ULg; Jérôme, Robert ULg

in Macromolecular Symposia (2003), 194

Polyolefinic microcomposites and layered silicate nanocomposites were prepared by the in-situ polymerization of ethylene (and alpha-olefin) via the so-called polymerization-filling technique. Various ... [more ▼]

Polyolefinic microcomposites and layered silicate nanocomposites were prepared by the in-situ polymerization of ethylene (and alpha-olefin) via the so-called polymerization-filling technique. Various tillers with either basic, acidic, metallic or carbonaceous surface, as well as non-modified clays such as montmorillonite and hectorite, were first treated by trimethylaluminum-depleted methylaluminoxane before being contacted by a titanium or zirconium-based metallocene catalyst. The (nano)composite was formed by addition and polymerization of ethylene (and alpha-olefin). This technique makes possible the complete encapsulation of every filler particle within the (co)polyolefinic matrix ranging from thermoplastics to elastomers. The so-obtained (nano)composites, often coined as "homogeneous" (nano)composites, exhibit improved mechanical properties; as compared to more conventional melt blends for a same filler content. [less ▲]

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See detailPolymer/layered silicate nanocomposites by combined intercalative polymerization and melt intercalation: a masterbatch process
Lepoittevin, Bénédicte; Pantoustier, Nadège; Devalckenaere, Myriam et al

in Polymer (2003), 44(7), 2033-2040

Poly(ε-caprolactone) (PCL) and poly(vinyl chloride) (PVC) layered silicate nanocomposites were prepared by combination of intercalative polymerization and melt intercalation. In a first step, high clay ... [more ▼]

Poly(ε-caprolactone) (PCL) and poly(vinyl chloride) (PVC) layered silicate nanocomposites were prepared by combination of intercalative polymerization and melt intercalation. In a first step, high clay content PCL nanocomposites were prepared by in situ polymerization of -caprolactone intercalated between selected organo-modified silicate layers. The polymerization was catalyzed with dibutyltin dimethoxide in the presence of montmorillonites, the surface of which were previously exchanged with (functionalized) long alkyl chains ammonium cations. Then, these highly filled PCL nanocomposites were added as masterbatches in commercial PCL and PVC by melt blending. The intercalation of PCL chains within the silicate layers by in situ polymerization proved to be very efficient, leading to the formation of intercalated and/or exfoliated structures depending on the organo-clay. These masterbatches were readily dispersed into the molten PCL and PVC matrices yielding intercalated/exfoliated layered silicate nanocomposites which could not be obtained by melt blending the matrix directly with the same organo-modified clays. The formation of nanocomposites was assessed both by X-ray diffraction and transmission electronic microscopy. Interestingly, this so-called 'masterbatch' two-step process allowed for preparing PCL nanocomposites even with non-modified natural clay, i.e. sodium montmorillonite, which showed a material stiffness much higher than the corresponding microcomposites recovered by direct melt intercalation. The thermal stability of PCL nanocomposites as a function of clay content was investigated by thermogravimetry (TGA). [less ▲]

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See detailPreparation of supported yttrium alkoxides as catalysts for the polymerization of lactones and oxirane
Martin, Eric; Dubois, Philippe ULg; Jérôme, Robert ULg

in Journal of Polymer Science. Part A, Polymer Chemistry (2003), 41(4), 569-578

Two methods have been reported that allow yttrium alkoxides to be supported on porous silica and to be used afterward as heterogeneous catalysts in the ring-opening polymerization of oxirane and e ... [more ▼]

Two methods have been reported that allow yttrium alkoxides to be supported on porous silica and to be used afterward as heterogeneous catalysts in the ring-opening polymerization of oxirane and e-caprolactone. In the two methods, [tris(hexamethyldisilyl)-amide]yttrium [Y[N(SiMe3)(2)](3)} is the metal alkoxide precursor. It is directly reacted with the silanol groups of the support, in the first method, and this is followed by alcoholysis of the unreacted amide groups. The flexibility of this method seems to be limited because the grafting density and the structure of the grafted Y alkoxide (less than one alkoxide by metal) are independent of the experimental conditions. In the second method, Y[N(SiMe3)(2)](3) is first reacted with 1 or 2 equiv of alcohol with the formation of the mixed Y alkoxide/amide. The amide functions are used to attach Y to the support. This method is free from side reactions, quite reproducible, and well suited to support one type of active species (monoalkoxide or dialkoxide). Preliminary experiments with e-caprolactone polymerization have confirmed the activity of the supported Y alkoxide, whatever preparation method is used. (C) 2003 Wiley Periodicals, Inc. [less ▲]

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See detailNew nanocomposite materials based on plasticized poly(L-lactide) and organo-modified montmorillonites: thermal and morphological study
Paul, Marie-Amélie; Degée, Philippe; Henrist, Catherine ULg et al

in Polymer (2003), 44(2), 443-450

Plasticized poly(L-lactide) (PLA) based nanocomposites were prepared by melt blending of the matrix with 20 wt% of poly(ethyleneglycol) 1000 (PEG 1000) and different amounts of montmorillonite, organo ... [more ▼]

Plasticized poly(L-lactide) (PLA) based nanocomposites were prepared by melt blending of the matrix with 20 wt% of poly(ethyleneglycol) 1000 (PEG 1000) and different amounts of montmorillonite, organo-modified or not. The intercalation of the polymer chains between the aluminosilicates layers and morphological structure of the filled PLAs were analysed by wide-angle X-ray scattering (WAXS). Thermogravimetric analyses (TGA) and differential scanning calorimetry (DSC) were performed to study the thermal behaviour of the prepared composites. At constant filler level, it appears that from all the clays studied, the montmorillonite organo-modified by bis-(2-hydroxyethyl)methyl (hydrogenated tallowalkyl) ammonium cations brings the greater effect in terms of thermal stability. Increasing the amount of clay allows to delay the onset of thermal degradation of the plasticized polymer matrix. It was also pointed out, by WAXS and DSC analyses, that it exists a real competition between PEG 1000 and PLA for the intercalation into the interlayer spacing of the clay. (C) 2002 Elsevier Science Ltd. All rights reserved. [less ▲]

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