References of "Jérôme, Christine"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailDual stimuli-responsive coating designed through layer-by-layer assembly of PAA-b-PNIPAM block copolymers for the control of protein adsorption
Osypova, Alina; Magnin, Delphine; Sibret, Pierre ULg et al

in Soft Matter (2015), 11(41), 8154-8164

In this paper, we describe the successful construction, characteristics and interaction with proteins of stimuli-responsive thin nanostructured films prepared by layer-by-layer (LbL) sequential assembly ... [more ▼]

In this paper, we describe the successful construction, characteristics and interaction with proteins of stimuli-responsive thin nanostructured films prepared by layer-by-layer (LbL) sequential assembly of PNIPAM-containing polyelectrolytes and PAH. PAA-b-PNIPAM block copolymers were synthesized in order to benefit from (i) the ionizable properties of PAA, to be involved in the LbL assembly, and (ii) the sensitivity of PNIPAM to temperature stimulus. The impact of parameters related to the structure and size of the macromolecules (their molecular weight and the relative degree of polymerization of PAA and PNIPAM), and the interaction with proteins under physico-chemical stimuli, such as pH and temperature, are carefully investigated. The incorporation of PAA-b-PNIPAM into multilayered films is shown to be successful whatever the block copolymer used, resulting in slightly thicker films than the corresponding (PAA/PAH)n film. Importantly, the protein adsorption studies demonstrate that it is possible to alter the adsorption behavior of proteins on (PAA-b-PNIPAM/PAH)n surfaces by varying the temperature and/or the pH of the medium, which seems to be intimately related to two key factors: (i) the ability of PNIPAM units to undergo conformational changes and (ii) the structural changes of the film made of weak polyelectrolytes. The simplicity of construction of these PNIPAM block copolymer-based LbL coatings on a large range of substrates, combined with their highly tunable features, make them ideal candidates to be employed for various biomedical applications requiring the control of protein adsorption. [less ▲]

Detailed reference viewed: 19 (5 ULg)
Full Text
Peer Reviewed
See detailSmall Angle X-ray Scattering Insights into the Architecture-Dependent Emulsifying Properties of Amphiphilic Copolymers in Supercritical Carbon Dioxide
Alaimo, David ULg; Hermida Merino, Daniel; Grignard, Bruno ULg et al

in Journal of Physical Chemistry B (2015), 119

The supramolecular assembly of a series of copolymers combining a PEO-rich hydrophilic and fluorinated CO2-philic sequences is analysed by synchrotron small-angle xray scattering (SAXS) in supercritical ... [more ▼]

The supramolecular assembly of a series of copolymers combining a PEO-rich hydrophilic and fluorinated CO2-philic sequences is analysed by synchrotron small-angle xray scattering (SAXS) in supercritical CO2, as well as in water/CO2 emulsions. These copolymers were designed to have the same molecular weight and composition, and to differ only by their macromolecular architecture. The investigated copolymers have random, block, and palm-tree architectures. Besides, thermo-responsive copolymer is also analysed, having a hydrophilic sequence becoming water-insoluble around 41 °C, i.e. just above the critical point of CO2. At the length scale investigated by SAXS, only the random copolymer appears to self-assemble in pure CO2, in the form of a disordered microgel-like network. The random, block and thermo-responsive copolymers are all able to stabilize water/CO2 emulsions but not the copolymer with the palm-tree architecture, pointing at the importance of macromolecular architecture for the emulsifying properties. A modelling of the SAXS data shows that the block and the thermo-responsive copolymers form spherical micelle-like structures containing about 70 % water and 30 % polymer. [less ▲]

Detailed reference viewed: 159 (22 ULg)
Full Text
Peer Reviewed
See detailImproved photo-induced cobalt-mediated radical polymerization in continuous flow photoreactors
Kermagoret, Anthony; Wenn, Benjamin; Debuigne, Antoine ULg et al

in Polymer Chemistry (2015), 6

The implementation of cobalt-mediated radical polymerization (CMRP) for continuous microreactor synthesis is described. We demonstrate how the utilization of flow photoreactors allows the speed up of the ... [more ▼]

The implementation of cobalt-mediated radical polymerization (CMRP) for continuous microreactor synthesis is described. We demonstrate how the utilization of flow photoreactors allows the speed up of the polymerization of vinyl acetate (VAc) under UV irradiation without loss of polymerization control. Microfluidics under UV irradiation has also been successfully implemented for the copolymerization of VAc with a less reactive olefin 1-octene (1-Oct). Reactivity ratios were deduced for this copolymerization system, and poly(VAc-co-1-Oct) copolymers containing up to 50 mol% of 1-Oct were synthesized. To the best of our knowledge, this is the first report on a photopolymerization where continuous flow techniques not only led to an improvement of reaction rates and dispersity, but also led to the avoidance of significant side-products that were observed in batch processing [less ▲]

Detailed reference viewed: 20 (2 ULg)
Full Text
Peer Reviewed
See detailBranched and linear A2–D–A1–D–A2 isoindigo-based solution-processable small molecules for organic field-effect transistors and solar cells
Tomassetti, Mirco ULg; Ouhib, Farid ULg; Cardinaletti, Ilaria et al

in RSC Advances (2015), 5(104), 85460-85469

To establish a correlation between the molecular structure, physicochemical properties, thin film morphology, charge carrier mobility and photovoltaic performance of isoindigo-based electron donor type ... [more ▼]

To establish a correlation between the molecular structure, physicochemical properties, thin film morphology, charge carrier mobility and photovoltaic performance of isoindigo-based electron donor type molecular semiconductors, a series of branched and linear A2–D–A1–D–A2 small molecules (A = acceptor, D = donor) are synthesized. The extended π-conjugated molecular chromophores have an electron-accepting isoindigo core, a bridging oligothiophene electron donor part and terminal octyl cyanoacrylate acceptor moieties. Their photophysical, thermal and electrochemical properties are analysed and the materials are applied in organic field-effect transistors and bulk heterojunction organic solar cells. Compared to an analogous benzothiadiazole-based small molecule, the isoindigo core deepens the HOMO energy level, enabling higher open-circuit voltages in organic solar cells. The linear isoindigo-based small molecule shows an enhanced hole mobility compared to the branched derivatives. The best power conversion efficiency of the investigated set is also obtained for the solar cell based on the linear (CA-3T-IID-3T-CA-l) donor molecule in combination with PC71BM. [less ▲]

Detailed reference viewed: 21 (4 ULg)
Full Text
Peer Reviewed
See detailRAFT polymerization of an alkoxyamine bearing acrylate, towards a well-defined redox active polyacrylate
Aqil, Mohamed ULg; Aqil, Abdelhafid ULg; Ouhib, Farid ULg et al

in RSC Advances (2015), 5(103), 85035-85038

A new strategy for the synthesis of a well-defined redox active poly- mer, a polyacrylate bearing TEMPO, and its grafting onto a gold substrate is described. It consists of polymerizing an acrylate ... [more ▼]

A new strategy for the synthesis of a well-defined redox active poly- mer, a polyacrylate bearing TEMPO, and its grafting onto a gold substrate is described. It consists of polymerizing an acrylate bearing an alkoxyamine by RAFT, followed by aminolysis of the trithiocar- bonate chain-end into a thiol that is exploited for the polymer grafting onto the gold sensor. Thermal activation of the alkoxyamine under air provides the redox polymer with a high yield. Its electroactivity is evaluated by a electrochemical quartz crystal microbalance (EQCM). [less ▲]

Detailed reference viewed: 25 (3 ULg)
Full Text
Peer Reviewed
See detailOrganocatalytic synthesis of bio-based cyclic carbonates from CO2 and vegetable oils
Alves, Margot ULg; Grignard, Bruno ULg; Gennen, Sandro ULg et al

in RSC Advances (2015), 5

Bio-based cyclic carbonates were synthesized by coupling CO2 with epoxidized linseed oil using a catalytic platform composed of a bicomponent organocatalyst. A screening of the catalytic activity of a ... [more ▼]

Bio-based cyclic carbonates were synthesized by coupling CO2 with epoxidized linseed oil using a catalytic platform composed of a bicomponent organocatalyst. A screening of the catalytic activity of a series of organic salts and ionic liquids used in combination with (multi)phenolic or fluorinated hydrogen bond donors was realized before highlighting the synergistic effect between the organocatalyst and the most efficient cocatalysts. These kinetics studies, followed by IR spectroscopy under pressure, enabled to optimize the reaction conditions and to provide quantitative formation of the cyclocarbonated vegetable oil in short reaction time without using any organic solvent. [less ▲]

Detailed reference viewed: 56 (11 ULg)
Full Text
Peer Reviewed
See detailNanocomposite foams of polypropylene and carbon nanotubes: preparation, characterization, and evaluation of their performance as EMI absorbers
Tran, Minh-Phuong; Thomassin, Jean-Michel ULg; Alexandre, Michaël et al

in Macromolecular Chemistry and Physics (2015), 216(12), 1302-1312

Highly expanded nanocomposite foams of polypropylene and carbon nanotubes (PP/CNT) are formed using supercritical carbon dioxide (scCO 2 ) technology. The foaming parameters (temperature, pressure) are ... [more ▼]

Highly expanded nanocomposite foams of polypropylene and carbon nanotubes (PP/CNT) are formed using supercritical carbon dioxide (scCO 2 ) technology. The foaming parameters (temperature, pressure) are investigated to establish their infl uence on the morphology of the resulting foams and their impact on the electrical con- ductivity. As promising electromagnetic-interference (EMI) absorbers, the EMI shielding performance of the foams is determined, and a preliminary relationship is established between foam morphology and the EMI shielding perfor- mance. The best candidates are highly expanded foams with a volume expansion of >25, containing 0.1 vol% CNTs; they are able to absorb more than 90% of the incident radiation between 25 and 40 GHz. [less ▲]

Detailed reference viewed: 61 (10 ULg)
Full Text
Peer Reviewed
See detailPreparation and characterizations of EGDE crosslinked chitosan electrospun membranes
Aqil, Abdelhafid ULg; Tchemtchoua, Victor T.; Colige, Alain ULg et al

in Clinical Hemorheology and Microcirculation (2015), 60(1), 39-50

Composite Crosslinked nanofibrous membranes of chitosan, ethylene glycol diglycidyl ether (EGDE) and polyethy- 10 lene oxide was successfully prepared with bead free morphology via electrospinning ... [more ▼]

Composite Crosslinked nanofibrous membranes of chitosan, ethylene glycol diglycidyl ether (EGDE) and polyethy- 10 lene oxide was successfully prepared with bead free morphology via electrospinning technique followed by heat mediated 11 chemical crosslinking. Architectural stability of nanofiber mat in aqueous medium was achieved by chemical crosslinking of 12 only 1% EGDE, and tensile strength tests revealed that increasing EGDE content has considerably enhance the elastic modu- 13 lus of nanofibers. The structure, morphology and mechanical properties of nanofibers were characterized by Attenuated Total 14 Reflection-Fourier Transform Infrared spectroscopy (ATR–FTIR), scanning electron microscopy (SEM) and Instron machine, 15 respectively. Skin fibroblasts and endothelial cells showedgood attachment, proliferation and viability on crosslinked electrospun 16 membranes. The results indicate a good biocompatibility and non-toxic nature of the resulted membrane. [less ▲]

Detailed reference viewed: 45 (17 ULg)
Full Text
Peer Reviewed
See detailPoly(ethylene glycol) grafted polylactide based copolymers for the preparation of PLA-based nanocarriers and hybrid hydrogel
Riva, Raphaël ULg; Schmeits, Stéphanie; Croisier, Florence ULg et al

in Clinical Hemorheology and Microcirculation (2015), 60

In previous works, poly(D,L-lactide-co-?CL-poly(ethylene glycol) (poly(D,L-La-co-?PEG?CL) amphiphilic graft- 10 copolymers were successfully synthesized according to a copper azide-alkyne cycloaddition ... [more ▼]

In previous works, poly(D,L-lactide-co-?CL-poly(ethylene glycol) (poly(D,L-La-co-?PEG?CL) amphiphilic graft- 10 copolymers were successfully synthesized according to a copper azide-alkyne cycloaddition (CuAAC) strategy. This paper aims 11 at reporting on the behavior of this amphiphilic copolymer in water, which was not studied in the previous paper. Moreover, 12 the ability of the copolymer to stabilize a PLA nanoparticles aqueous suspension is presented. For this purpose, dynamic 13 light scattering (DLS) and transmission electron microscopy (TEM) are proposed to characterize the nanoparticles in solution. 14 Otherwise, the strategy developed for the synthesis of the amphiphilic copolymers was adapted and extended to the synthesis of 15 PLA-based degradable hydrogel, potentially applicable as drug-loaded degradable polymer implant. [less ▲]

Detailed reference viewed: 46 (8 ULg)
Full Text
Peer Reviewed
See detailSynthesis and tensioactive properties of PEO-b-polyphosphate copolymers
Vanslambrouck, Stéphanie ULg; Clément, Benoit; Riva, Raphaël ULg et al

in RSC Advances (2015), 5(35), 27330-37337

Poly(ethylene oxide) (PEO)-b-polyphosphate copolymers made of hydrophilic PEO and hydrophobic polyphosphates are amphiphilic copolymers prone to self-assemble in water into nanoparticles. In this work ... [more ▼]

Poly(ethylene oxide) (PEO)-b-polyphosphate copolymers made of hydrophilic PEO and hydrophobic polyphosphates are amphiphilic copolymers prone to self-assemble in water into nanoparticles. In this work, nanoparticles are obtained by the self-assembly of PEO-b-polyphosphate copolymers in water in the absence of any organic co-solvent whatever the length of the pendant alkyl chain (between 4 and 7 carbon atoms) of the polyphosphate block. Remarkably, this solvent-free process remains efficient even for the most hydrophobic polyphosphate blocks. The critical aggregation concentration (CAC) of the block copolymers was determined by pyrene probe fluorescence. Finally, the efficiency of these copolymer surfactants to decrease the air–water interface was measured by air-bubble tensiometry. [less ▲]

Detailed reference viewed: 58 (16 ULg)
Full Text
Peer Reviewed
See detailDirect route to well-defined poly(ionic liquid)s by controlled radical polymerization in water
Cordella, Daniela ULg; Kermagoret, Anthony ULg; Debuigne, Antoine ULg et al

in ACS Macro Letters (2014), 3

The precision synthesis of poly(ionic liquid)s (PILs) in water is achieved for the first time by the cobalt-mediated radical polymerization (CMRP) of N-vinyl-3-alkylimidazolium-type monomers following two ... [more ▼]

The precision synthesis of poly(ionic liquid)s (PILs) in water is achieved for the first time by the cobalt-mediated radical polymerization (CMRP) of N-vinyl-3-alkylimidazolium-type monomers following two distinct protocols. The first involves the CMRP of various 1-vinyl-3-alkylimidazolium bromides conducted in water in the presence of an alkyl–cobalt(III) complex acting as a monocomponent initiator and mediating agent. Excellent control over molar mass and dispersity is achieved at 30 °C. Polymerizations are complete in a few hours, and PIL chain-end fidelity is demonstrated up to high monomer conversions. The second route uses the commercially available bis(acetylacetonato)cobalt(II) (Co(acac)2) in conjunction with a simple hydroperoxide initiator (tert-butyl hydroperoxide) at 30, 40, and 50 °C in water, facilitating the scaling-up of the technology. Both routes prove robust and straightforward, opening new perspectives onto the tailored synthesis of PILs under mild experimental conditions in water. [less ▲]

Detailed reference viewed: 58 (12 ULg)
Full Text
Peer Reviewed
See detailNanocomposites based on MWCNT and polystyrene, styrene-acrylonitrile copolymer, or polymethylmethacrylate, obtained by miniemulsion polymerization
Donescu, Dan; Corobea, Mihai Cosmin; Petcu, Cristian et al

in Journal of Applied Polymer Science (2014), 131(23), 411481-10

Free radical miniemulsion polymerization of styrene (St), St/acrylonitrile 3 : 1 mixture or methylmethacrylate in the presence of multiwalled carbon nanotubes (MWCNT) was proven as a convenient way to ... [more ▼]

Free radical miniemulsion polymerization of styrene (St), St/acrylonitrile 3 : 1 mixture or methylmethacrylate in the presence of multiwalled carbon nanotubes (MWCNT) was proven as a convenient way to obtain homogenous hybrids with perspectives in associated applications like foams specialties materials. Miniemulsion polymerization was viable up to 2% wt. MWCNT to monomer, without agglomerations. The grafting on MWCNT during the polymerization occurs without the need for supplementary functionalization and the polymer grafted nanotubes showed stable dispersions in the polymer solvent. Monomer polarity affected the grafting ability during the polymerization process. The nanocomposites obtained after purification and drying were used in foaming process. MWCNT presence in the related nanocomposites decreased the pore sizes in foam-like materials (for all three different matrices). At 1 wt % MWCNT content, low density (< 0.3 g/cm3), low pore size (< 10 μm) and high cell density (>109 cell/cm3) were achieved. [less ▲]

Detailed reference viewed: 68 (4 ULg)
Full Text
Peer Reviewed
See detailPolysaccharide-coated PCL nanofibers for wound dressing applications
Croisier, Florence ULg; Atanasova, Ganka; Poumay, Yves et al

in Advanced Healthcare Materials (2014), 3(12), 2032-2039

Polysaccharide-based nanofibers with amultilayered structure are prepared by combining electrospinning (ESP) and layer-by-layer (LBL) deposition techniques. Charged nanofibers are firstly prepared by ... [more ▼]

Polysaccharide-based nanofibers with amultilayered structure are prepared by combining electrospinning (ESP) and layer-by-layer (LBL) deposition techniques. Charged nanofibers are firstly prepared by electrospinning poly(ε-caprolactone) (PCL) with a block-copolymer bearing carboxylic acid functions. After deprotonation of the acid groups, the layer-by-layer deposition of polyelectrolyte polysaccharides, notably chitosan and hyaluronic acid, is used to coat the electrospun fibers. A multilayered structure is achieved by alternating the deposition of the positively charged chitosan with the deposition of a negatively charged polyelectrolyte. The construction of this multi-layered structure is followed by Zeta potential measurements, and confirmed by observation of hollow nanofibers resulting from the dissolution of the PCL core in a selective solvent. These novel polysaccharide-coated PCL fiber mats remarkably combine the mechanical resistance typical of the core material (PCL) – particularly in the hydrated state –, with the surface properties of chitosan. The control of the nanofiber structure offered by the electrospinning technology, makes the developed process very promising to precisely design biomaterials for tissue engineering. Preliminary cell culture tests corroborate the potential use of such system in wound healing applications. [less ▲]

Detailed reference viewed: 103 (12 ULg)
Full Text
Peer Reviewed
See detailPoly( N-vinylcaprolactam): A thermoresponsive macromolecule with promising future in biomedical field
Liu, Ji; Debuigne, Antoine ULg; Detrembleur, Christophe ULg et al

in Advanced Healthcare Materials (2014), 3(12), 1941-1968

Poly( N -vinylcaprolactam) (PNVCL) is a thermoresponsive and biocompatible polymer that raises an increasing interest in the biomedical area, especially in drug delivery systems (DDS) that include ... [more ▼]

Poly( N -vinylcaprolactam) (PNVCL) is a thermoresponsive and biocompatible polymer that raises an increasing interest in the biomedical area, especially in drug delivery systems (DDS) that include micelles, hydrogels, and hybrid particles. The thermoresponsiveness of PNVCL, used alone or in combination with other stimuli- responsive polymers or particles (pH, magnetic fi eld, or chemicals), is often key in the loading and/or release process in these DDS. The renewed focus on this polymer, which is known for decades, is to a large extent due to recent progress in synthetic strategies. Especially, the advent of efficient controlled radical polymerization (CRP) methods for NVCL monomer gives now access to unprecedented well-defi ned NVCL-based copolymers with unique properties. This Review article addresses up-to-date synthetic aspects, biological features, and biomedical applications of the latest NVCL-containing systems. [less ▲]

Detailed reference viewed: 98 (11 ULg)
Full Text
Peer Reviewed
See detailInput of supercritical carbon dioxide to polymer synthesis: an overview
Boyère, Cédric; Jérôme, Christine ULg; Debuigne, Antoine ULg

in European Polymer Journal (2014), 61

The ongoing search for environmentally friendlier alternative to the organic solvents used in chemical processes has led to the development of technologies based on supercritical carbon dioxide (scCO2 ... [more ▼]

The ongoing search for environmentally friendlier alternative to the organic solvents used in chemical processes has led to the development of technologies based on supercritical carbon dioxide (scCO2), which is non-flammable, non-toxic and relatively inert fluid. Polymer chemistry does not escape this trend and last achievements in the field of polymer synthesis in scCO2 are reviewed here. Without claiming to be exhaustive, we go through and discuss the benefits of the main polymerization processes in scCO2 including homogeneous, precipitation, dispersion, suspension and emulsion systems. A particular attention is drawn to water/carbon dioxide emulsion polymerization and to the suited surface active agents. This review also underlines that heterogeneous polymerization based on CO2 is more than a strategy for reducing the ecological footprint of the polymer production but it allows structuring the polymer materials into particles or highly interconnected macroporous networks. [less ▲]

Detailed reference viewed: 86 (9 ULg)
Full Text
See detailRole of the polyQ length and non-polyQ regions during the aggregation process into amyloid fibrils of model polyQ proteins
Huynen, Céline ULg; Willet, Nicolas ULg; Buell, Alexander K et al

Poster (2014, November 26)

Nine neurodegenerative disorders, referred to as polyglutamine diseases and including Huntington’s disease, are associated with the abnormal expansion of a polyglutamine tract inside nine unrelated ... [more ▼]

Nine neurodegenerative disorders, referred to as polyglutamine diseases and including Huntington’s disease, are associated with the abnormal expansion of a polyglutamine tract inside nine unrelated proteins. This polyQ expansion is thought to be the major determinant in the development of neurotoxicity, triggering protein aggregation into amyloid fibrils. A large body of evidence however suggests that non-polyQ regions modulate the aggregation process triggered by polyQ expansions. The interplay between the polyQ tract and non-polyQ regions is complex and still not fully understood. In order to better understand it, we previously designed and characterized model polyQ proteins made of the beta-lactamase BlaP with 23, 30, 55 and 79Q inserted at position 197 or 216. Our first results had indicated that our model is relevant to study polyQ aggregation since it recapitulates the aggregation properties of polyQ disease-associated proteins: there is a Q-threshold for the spontaneous formation of amyloid fibrils in solution, and above the threshold, the longer the polyQ, the faster the aggregation. Moreover, the structure of BlaP and the position of insertion of the polyQ tract influence their aggregation properties in solution. This work aims to better understand, at the molecular level, (i) the precise role of the polyQ length (23, 30, 55, 61, 67, 73 and 79Q), (ii) the conformation of the host protein (native or unfolded BlaP), (iii) the location of the polyQ tract within BlaP (197 or 216), (iv) the flexibility of the polyQ flanking sequences, and (v) the origin of constraints applied by BlaP to the inserted polyQ tract (at its N- or C-terminal end) on the structural, thermodynamic and aggregation properties of BlaP-polyQ chimeras, using a wide range of biophysical techniques (e.g., spectroscopy methods, quartz crystal microbalance, atomic force microscopy and dynamic light scattering). The effect on the aggregation properties will be determined on the spontaneous aggregation into amyloid fibrils in solution, and on the nucleation and on the elongation steps of amyloid fibril formation. For this purpose, new chimeras containing 61, 67 and 73Q at position 197, or 55Q inserted at position 197 in between two different protease’s cleavage sites, that are relatively flexible, will be moreover created. Our results first demonstrate that the spontaneous aggregation into amyloid fibrils in solution is correlated to the polyQ length with an exponential growth function, and that the elongation rate is linearly correlated to the polyQ length, independently of the protein context (i.e., conformation of BlaP, and/or location of the polyQ tract, and/or polyQ peptides inserted or not within BlaP). However, the location of the polyQ tract inside BlaP, and/or its conformational state, and/or the flexibility of polyQ flanking sequences, and/or the origin of constraints applied to the polyQ tract drastically influence the ability of a polyQ tract to trigger the nucleation and/or the elongation step of amyloid fibrils (variation in the Q-threshold and in the absolute rate of both steps). Altogether, our results suggest that non-polyQ regions constitute an additional potential therapeutic target, more specific than drugs targeting the polyQ sequence, to interfere with the nucleation and/or the elongation of amyloid fibrils, associated to neurotoxicity. A possible drug could be constituted by a ligand specific to non-polyQ regions of disease-associated proteins, which further increases the constraints applied to the polyQ expansion to prevent the disease onset and/or progression. [less ▲]

Detailed reference viewed: 39 (8 ULg)
Full Text
Peer Reviewed
See detailDouble thermoresponsive di- and triblock copolymers based on N-vinylcaprolactam and N-vinylpyrrolidone: synthesis and comparative study of solution behaviour
Kermagoret, Anthony ULg; Mathieu, Kevin ULg; Thomassin, Jean-Michel ULg et al

in Polymer Chemistry (2014), 5(22), 6534-6544

Poly(N-vinylcaprolactam) (PNVCL) and poly(N-vinylpyrrolidone) (PNVP) are water soluble polymers of interest especially in the biomedical field. Moreover, PNVCL is characterized by a lower critical ... [more ▼]

Poly(N-vinylcaprolactam) (PNVCL) and poly(N-vinylpyrrolidone) (PNVP) are water soluble polymers of interest especially in the biomedical field. Moreover, PNVCL is characterized by a lower critical solution temperature close to 36 °C in water, which makes it useful for the design of thermoresponsive systems. In this context, we used the cobalt-mediated radical polymerization (CMRP) and reaction coupling (CMRC) for synthesizing a series of well-defined NVCL and NVP-based copolymers, including statistical copolymers as well as double thermoresponsive diblocks and triblocks. Dynamic light scattering and turbidimetry analyses highlighted the crucial impact of the copolymer composition and architecture on the cloud point temperature (TCP) of each segment and also their influence on the multistep assembly behaviour of block copolymers. Addition of NaCl enabled us to adjust the inter-TCP range of the di- and triblock in which selective precipitation of one block and self-assembly of the copolymer were favoured. Overall, data presented here provide a basis for the synthesis of a broad range of NVCL/NVP based copolymer architectures with a tunable thermal response in water. [less ▲]

Detailed reference viewed: 54 (14 ULg)
See detailRecyclable shape-memory materials based on photo or thermo-reversible crosslinking
Defize, Thomas ULg; Riva, Raphaël ULg; Wauters, Céline et al

Poster (2014, November 11)

Shape memory polymers (SMPs) are remarkable materials able to switch from a stressed deformed state (temporary shape) to their initial relaxed state (permanent shape) by the application of a stimulus ... [more ▼]

Shape memory polymers (SMPs) are remarkable materials able to switch from a stressed deformed state (temporary shape) to their initial relaxed state (permanent shape) by the application of a stimulus, such as heat or light. Typically, the shape memory property is generally observed for chemically or physically cross-linked polymers that exhibit an elastomeric behavior above a phase transition, e.g. glass or melting transition. Cross-linked semi-crystalline poly(ε-caprolactone) (PCL) is already widely studied for the development of SMPs. However, the tensile strength of standard PCL-based SMPs remains quite low, limiting their use in some applications. A convenient way to enhance the strength of SMPs relies on the introduction of nanofillers, such as silica nanoparticles, leading to an enhancement of mechanical strength. Moreover, silica nanoparticles can be advantageously used as multifunctional crosslinking nodes, with the purpose to increase the cross-linking density of the material. As most of SMPs are irreversibly cross-linked material, their reprocessing is impossible preventing any recycling. Thereby, reversible reactions, allowing the formation/cleavage of the network, raise tremendous interest in macromolecular engineering. Recently, a reversibly cross-linked 4-arm star-shaped PCL-based SMP was prepared using the Diels-Alder (DA) reaction between furan and maleimide moieties, well-known to create reversible bonds. This shape memory material demonstrated to be implementable, and so recyclable, and was characterized by excellent fixity and recovery before and after recycling experiments. However, the relatively low retro-DA temperature of the furan- maleimide adducts led to an inelastic deformation during shape memory tensile cycles. In order to get rid of this drawback, two alternative approaches were investigated. Firstly, the substitution of the DA reaction by a photo-reversible reaction, typically the photo- induced (2+2) cycloaddition of coumarins, was proposed to crosslink the PCL matrix. The second approach is based on the use of surface functionalized silica nanoparticles as crosslinking nodes with the purpose to increase the crosslinking density of the material. The network formation and cleavage were studied by solid-state NMR and rheology.4 The resulting shape memory materials were characterized by excellent one-way and two-way shape memory properties as demonstrated by dynamical mechanical analysis. [less ▲]

Detailed reference viewed: 52 (2 ULg)
See detailSmart cross-linked polymer micelles for drug delivery
Riva, Raphaël ULg; Vanslambrouck, Stéphanie ULg; Ergül, Zeynep ULg et al

Conference (2014, November 11)

Nowadays, polymer crosslinking is widely used in industry to improve or to impart new properties to existing polymer material. In the pharmaceutical field, polymer crosslinking is of great interest for ... [more ▼]

Nowadays, polymer crosslinking is widely used in industry to improve or to impart new properties to existing polymer material. In the pharmaceutical field, polymer crosslinking is of great interest for the elaboration of drug delivery devices, mostly hydrogels. Nevertheless, crosslinking is also very useful in nanovectorization of active principle. Indeed, each day, new drugs are synthesized and available on the market but in too many cases, the high hydrophobicity of some drugs makes them useless because of the absence of an appropriated administration method. The encapsulation of the drug into a nanocarrier, typically in the hydrophobic core of a polymer micelle, allows a significant increase of the drugs concentration in water in addition to the protection of the active principle against degradation. However, polymer micelles suffer of the main drawback to not be stable, leading to a premature release of the drug, when the concentration falls down the critical micellar concentration (CMC), which it is rapidly observed after intravenous injection. In order to get rid of the CMC, crosslinking of the micelle core is the most proposed strategy. Nevertheless, the crosslinking of the micelle core may have a non-negligible effect on the drug loading but mainly on the drug release due to the sequestration of the drug in the network. Over the last years, our lab investigated several strategies for the crosslinking of the micelle core made of amphiphilic and biocompatible block copolymers generally by UV radiation in order to fulfill the increasingly stringent requirements of biomedical applications. These strategies are very helpful to prepare injectable nanosized cross-linked particles loaded with an active particle. For some systems, the effect of the crosslinking rate on the drug loading and the drug release was evaluated using a model drug. As the crosslinking may interfere with the drug release after internalization of the carrier into the cell, a reversible crosslinking of the micelle core was proposed. Typically, the introduction of disulfide bond as inter-chain links allowed to delay the drug release by diffusion whereas into the cell, the reduction of the disulfide bridges into corresponding thiol led to the fast disassemble of the micelle and the specific release of the drug into cytoplasm. [less ▲]

Detailed reference viewed: 168 (10 ULg)