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Vuong Q.L.,University of Mons | Berret J.-F.,University Paris Diderot | Fresnais J.,CNRS Analytical Sciences Lab | Gossuin Y.,University of Mons | Sandre O.,CNRS Organic Polymer Chemistry Laboratory
Advanced Healthcare Materials | Year: 2012

Magnetic particles are very efficient magnetic resonance imaging (MRI) contrast agents. In recent years, chemists have unleashed their imagination to design multi-functional nanoprobes for biomedical applications including MRI contrast enhancement. This study is focused on the direct relationship between the size and magnetization of the particles and their nuclear magnetic resonance relaxation properties, which condition their efficiency. Experimental relaxation results with maghemite particles exhibiting a wide range of sizes and magnetizations are compared to previously published data and to wellestablished relaxation theories with a good agreement. This allows deriving the experimental master curve of the transverse relaxivity versus particle size and to predict the MRI contrast efficiency of any type of magnetic nanoparticles. This prediction only requires the knowledge of the size of the particles impermeable to water protons and the saturation magnetization of the corresponding volume. To predict the T2 relaxation efficiency of magnetic single crystals, the crystal size and magnetization - obtained through a single Langevin fit of a magnetization curve - is the only information needed. For contrast agents made of several magnetic cores assembled into various geometries (dilute fractal aggregates, dense spherical clusters, core-shell micelles, hollow vesicles...), one needs to know a third parameter, namely the intra-aggregate volume fraction occupied by the magnetic materials relatively to the whole (hydrodynamic) sphere. Finally a calculation of the maximum achievable relaxation effect - and the size needed to reach this maximum - is performed for different cases: maghemite single crystals and dense clusters, core-shell particles (oxide layer around a metallic core) and zinc-manganese ferrite crystals. © 2012 WILEY-VCH Verlag GmbH & Co.KGaA, Weinheim. Source


Garanger E.,CNRS Organic Polymer Chemistry Laboratory | Lecommandoux S.,French National Center for Scientific Research
Angewandte Chemie - International Edition | Year: 2012

Interdisciplinary: The application of protein-engineering techniques to polymer materials can lead to the design and preparation of biocompatible, biodegradable, stimuli-sensitive copolymers bearing biologically responsive peptide motifs (see picture). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Tingaut P.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Zimmermann T.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Sebe G.,CNRS Organic Polymer Chemistry Laboratory
Journal of Materials Chemistry | Year: 2012

In this article, we highlight the potential of nanocelluloses, such as cellulose nanocrystals (CNC) and microfibrillated cellulose (MFC), to serve as building blocks for the design of hierarchical functional nanomaterials. Four categories of value-added nanomaterials are envisaged here, namely aerogels, emulsions, templated materials and stimuli-responsive nanodevices. But most importantly, we demonstrate that appropriate functionalization methods are required in order to tailor the nanocellulose surface and further design materials with required characteristics. © 2012 The Royal Society of Chemistry. Source


Dakshinamoorthy D.,CNRS Organic Polymer Chemistry Laboratory | Peruch F.,CNRS Organic Polymer Chemistry Laboratory
Journal of Polymer Science, Part A: Polymer Chemistry | Year: 2012

A series of di- and triblock copolymers [poly(L-lactide-b-μ- caprolactone), poly(D,L-lactide-b-μ-caprolactone), poly(μ-caprolactone-b- L-lactide), and poly(μ-caprolactone-b-L-lactide-b-μ-caprolactone)] have been synthesized successfully by sequential ring-opening polymerization of μ-caprolactone (μ-CL) and lactide (LA) either by initiating PCL block growth with living PLA chain end or vice versa using titanium complexes supported by aminodiol ligands as initiators. Poly(trimethylene carbonate-b-μ-caprolactone) was also prepared. A series of random copolymers with different comonomer composition were also synthesized in solution and bulk of μ-CL and D,L-lactide. The chemical composition and microstructure of the copolymers suggest a random distribution with short average sequence length of both the LA and μ-CL. Transesterification reactions played a key role in the redistribution of monomer sequence and the chain microstructures. Differential scanning calorimetry analysis of the copolymer also evidenced the random structure of the copolymer with a unique T g. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 A series of di- and triblock copolymers of μ-caprolactone, L-lactide, D,L-lactide, and trimethylene carbonate have been synthesized successfully by sequential ring-opening polymerization technique using titanium complexes supported by aminodiol ligands as initiators. It was shown that either μ-caprolactone or lactide could be polymerized first. Copolymers of μ-caprolactone and lactides with different composition were also synthesized both in solution and bulk conditions, revealing that transesterification reactions could play a significant role in the redistribution of monomer leading to random copolymers. Copyright © 2012 Wiley Periodicals, Inc. Source


Schappacher M.,CNRS Organic Polymer Chemistry Laboratory | Deffieux A.,CNRS Organic Polymer Chemistry Laboratory
Journal of the American Chemical Society | Year: 2011

A route to macrocyclic polymers based on a new unimolecular ring-closure process has been investigated. It involves the direct end-to-end coupling of an α,ω-bis[chloroiron(III) meso-tetraphenylporphyrin] telechelic linear polystyrene synthesized by living polymerization followed by chain-end functionalization. The corresponding macrocyclic polystyrene was obtained readily and selectively by intramolecular condensation of the α,ω-bis[chloroiron(III) meso-tetraphenylporphyrin] polymer ends in the presence of a base to yield a diiron(III)-μ-oxobis(porphyrin) dimer as ring-closing unit. Addition of dilute HCl was shown to rapidly reconvert the diiron(III)-μ-oxobis(porphyrin) unit into the initial bis[chloroiron(III) porphyrin], demonstrating the selectivity and complete reversibility of the cyclization process. The synthesis and detailed structural characterization of the α,ω-homodifunctional precursor and the corresponding macrocyclic polystyrene along with an analysis of the porphyrin dimerization reaction using NMR spectroscopy and size-exclusion chromatography coupled with a diode array detector are presented. © 2011 American Chemical Society. Source

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