Synthèse de copolymères "en peigne" et étude de leurs propriétés physico-chimiques en solution et en masse

Le développement des techniques des polymérisations ioniques dites "vivantes" et le besoin croissant de nouveaux matériaux polymères présentant des propriétés originales et innovantes ont ouvert de nouvelles voies en synthèse macromoléculaire. Ceci a permis l’élaboration de polymères dits "à architecture complexe" : polymères en peigne, cycliques, en étoile, hyper-ramifiés ou polymères à architecture dendritique. C’est dans ce cadre que trois familles distinctes d’architecture en peigne, constituée de chaînes polystyrène et polyisoprène, ont été synthétisées en utilisant des processus de polymérisation cationique et anionique� "vivants", couplés aux techniques de greffage "sur" et "à partir de". L’ensemble de ce protocole permet de contrôler les différents paramètres moléculaires tels que la longueur du tronc central, le nombre et la longueur des branches, l’agencement des différents blocs macromoléculaires constituant les objets, la masse molaire totale et enfin la distribution des masses molaires. Il permet également d’introduire à l’extrémité de chacune de ces branches des groupes fonctionnels divers. L’effet de l’architecture sur leur comportement a été étudié en solution et en masse. La première technique d’investigation utilisée, la diffusion de la lumière (DDL), a permis de déterminer les dimensions et l’état d’association de ces structures en bon solvant et en solvant sélectif de l’un des blocs. Cette technique a été couplée à la microscopie à force atomique (AFM) pour visualiser les molécules isolées et les phénomènes possibles de micellisation des différents copolymères en peigne. Des études par diffusion des rayons-x ont été également réalisées afin d’étudier la nano-organisation des peignes à l’état solide.A new class of polymers with complex macromolecular architecture has recently appeared (comb-like, cyclic, star-like, hyperbranched polymers or dendrigraft) thanks to the development of new techniques of synthesis such as ionic living polymerizations and to the growing needs for new types of polymer materials with original properties. In this context three types of comb-like polymers having polystyrene and polyisoprene side chains have been synthesized by ’grafting onto’ and ’grafting from’ techniques using anionic and cationic living polymerizations. By this approach we are able to control over, most of the parameters, such as chain length of backbone, number and size of branches, molar mass and dispersity. We could also introduce functional groups at each end of the side chains. After synthesizing different types of comb-like copolymer, the effect of polymer architecture on their behaviour has then been investigated in solution, in good and selective solvent, and in the bulk (films). The dimensions and self-assembly processes of comb-like polymers were investigated by dynamic light scattering, while atomic force microscopy was used to visualize individual molecules and their self-assembly. Nano-organization of the comb-like copolymers was studied in the solid by X-ra

Structure of synthetic K-rich birnessite obtained by high-temperature decomposition of KMnO4. I. Two-layer polytype from 800°C experiment.

International audienceThe structure of a synthetic potassium birnessite (KBi) obtained as a finely dispersed powder by thermal decomposition of KMnO4 at 800°C was for the first time studied by single crystal X-ray diffraction (XRD). It is shown that KBi has a two-layer cell with a = 2.840(1) Ä, and c = 14.03(1) Ä, and space group P63/mmc. In contrast to the structure model proposed by Kim et al., 1 the refined model demonstrates the sole presence of Mn4+ in the octahedral layers, the presence of 0.12 vacant layer sites per octahedron being responsible for the layer charge deficit. This layer charge deficit is compensated for 1) by the presence of interlayer Mn 3+ above or below vacant layer octahedra sharing three O layer with neighboring Mnlayer octahedra to form a triple-corner surface complex ( VITC sites), and 2) by the presence of interlayer K in prismatic cavities located above or below empty tridentate cavities, sharing three edges with neighboring Mnlayer octahedra ( VITE sites). As compared to the structure model proposed by Kim et al., 1 this VITE site is shifted from the center of the prismatic cavity towards its edges. A complementary powder XRD study confirmed the structure model of the main defect-free KBi phase and allowed to determine the nature of stacking disorder in a defective accessory KBi phase admixed to the defect-free KBi

Characterization of FUS Mutations in Amyotrophic Lateral Sclerosis Using RNA-Seq

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease resulting in severe muscle weakness and eventual death by respiratory failure. Although little is known about its pathogenesis, mutations in fused in sarcoma/translated in liposarcoma (FUS) are causative for familial ALS. FUS is a multifunctional protein that is involved in many aspects of RNA processing. To elucidate the role of FUS in ALS, we overexpressed wild-type and two mutant forms of FUS in HEK-293T cells, as well as knocked-down FUS expression. This was followed by RNA-Seq to identify genes which displayed differential expression or altered splicing patterns. Pathway analysis revealed that overexpression of wild-type FUS regulates ribosomal genes, whereas knock-down of FUS additionally affects expression of spliceosome related genes. Furthermore, cells expressing mutant FUS displayed global transcription patterns more similar to cells overexpressing wild-type FUS than to the knock-down condition. This observation suggests that FUS mutants do not contribute to the pathogenesis of ALS through a loss-of-function. Finally, our results demonstrate that the R521G and R522G mutations display differences in their influence on transcription and splicing. Taken together, these results provide additional insights into the function of FUS and how mutations contribute to the development of ALS.ALS Foundation NetherlandsAdessium FoundationSeventh Framework Programme (European Commission) (grant number 259867)Thierry Latran FoundationNational Institutes of Health (U.S.) (NIH/NINDS grant R01NS073873)National Institute of Neurological Disorders and Stroke (U.S.) (NIH/NINDS grant numbers 1R01NS065847

Synthèse de copolymères "en peigne" et étude de leurs propriétés physico-chimiques en solution et en masse

Le développement des techniques des polymérisations ioniques dites "vivantes" et le besoin croissant de nouveaux matériaux polymères présentant des propriétés originales et innovantes ont ouvert de nouvelles voies en synthèse macromoléculaire. Ceci a permis l'élaboration de polymères dits "à architecture complexe" : polymères en peigne, cycliques, en étoile, hyper-ramifiés ou polymères dendritique. C'est dans ce cadre que trois familles distinctes d'architecture en peigne, constituée de chaînes polystyrène et polyisoprène, ont été synthétisées en utilisant des processus de polymérisation cationique et anionique "vivante", couplés aux techniques de greffage "sur" et "à partir de". L'ensemble de ce protocole permet de contrôler les différents paramètres moléculaires tels que la longueur du tronc central, le nombre et la longueur des branches, l'agencement des branches, l'agencement des diiférents blocs macromoléculaires constituant les objets, la masse molaire totale et enfin la distribution des masses molaires. Il permet également d'introduire à l'extrémité de chacune de ces branches des groupes fonctionnels divers. L'effet de l'architcture sur leur comportement a été étudié en solution et en masse. La première technique d'investigation utilisée, la diffusion de la lumière (DDL), a permis de déterminer les dimensions et l'état d'association de ces structures en bon solvant et en solvant sélectif de l'un des blocs. Cette technique a été couplée à la miscroscopie à force atomique (AFM) pour visualiser les molécules isolées et les phénomènes possibles de micellisation des différents copolymères en peigne. Des études par diffusion des rayons-x ont été également réaliser afin d'étudier la nono-organisation des peignes à l'état solide.BORDEAUX1-BU Sciences-Talence (335222101) / SudocSudocFranceF

Synthesis of comblike poly(styrene-b-isoprene) block copolymers and their properties in good and selective solvents

Comblike block copolymers having a poly(chloroethyl vinyl ether) backbone and poly(styrene-b-isoprene) side chains, i.e., PCEVE-g-(PS-b-PI), of different molar masses and chemical compositions were synthesized by "grafting onto" technique using the coupling reaction of acetal-PSLi (F-PSLi) chains onto the reactive functions of a PCEVE backbone, followed, in a second step, by the grafting of living PIDLi chains onto the acetal ends of PS branches activated by trimethyl silyl iodide. The comblike copolymers exhibit low polydispersity, high molar masses, and a controlled number of branches. Their characteristics and behavior were further studied in the solid as thin films and in good and selective solvents. Atomic force microscopy (AFM) shows isolated uniform molecules that adopt an ovoid conformation. The solution behavior of these comblike polymers was investigated by dynamic light scattering (DLS), both in a good solvent of the PS and the PI blocks and in selective solvents of the outer PI blocks. Depending on the solvent quality and the temperature, the comblike copolymers, which remain in the form of isolated molecules, adopt different chain conformations and dimensions, as shown by the drastic variation of the radius of gyration. In a series of hydrocarbon solvents of decreasing quality for the inner PS block, the significant volume decrease of the macromolecule is attributed to the internal shrinkage of the PS blocks. In cyclohexane, a theta solvent for the inner PS block, a strong variation of the comblike size (90% volume change) takes place with the temperature change, directly correlated with the internal expansion/contraction of the inner PS blocks

Synthesis of (poly(chloroethyl vinyl ether)-g-polystyrene)comb-b-(poly(chloropyran ethoxy vinyl ether)-g-polyisoprene)comb copolymers and study of hyper-branched micelle formation in dilute solutions

Poly(styrene)comb-b-poly(isoprene)comb copolymers having a heterofunctional polyvinyl ether diblock backbone were synthesized by the grafting onto method. Their synthesis involves in a first step the selective coupling reaction of polystyryllithium chains onto the reactive chloroether functions of a poly(chloroethyl vinyl ether) first block while the second block poly(pyranethoxy vinyl ether) remains unchanged, yielding Poly(styrene)comb with a poly(pyranethoxy vinyl ether) tail. In a second step, living polyisoprenyllithium chains are grafted onto the second block previously modified to introduce reactive chlorobutyl functions. The obtained high molar masses PScomb-b-PIcomb copolymers exhibit a low polydispersity and a controlled number of branches. Their characteristics and behavior were further studied as isolated objects using imaging technique such as atomic force microscopy and using light scattering in a good solvent for PS and PI moieties, and in a selective solvent of PIcomb blocks. The PScomb-b-PIcomb copolymers adopt a cylindrical conformation in good solvent and self-assemble in micelles by association of the combPS blocks in heptane

Poly(styrene)comb-b-poly(ethylene oxide)comb copolymers: Synthesis and AFM investigation of intra- and supramolecular organization as thin deposits

PScomb-block-PEOcomb copolymers having a poly(chloroethyl vinyl ether)-b-poly(hydroxy ethyl vinyl ether) backbone with polystyrene chains on one side and poly(ethylene oxide) chains on the other, i.e. (PCEVE-g-PS)-b-(POHEVE-g-PEO), were synthesized. The strategy is based on grafting of polystyryllithium onto the reactive chloro functions of the poly(chloroethyl vinyl ether) first block and on grafting polyethylene oxide from the hydroxyl functions of the second block. This procedure allows the preparation of densely grafted amphiphilic diblocklike, Janus-type, comblike copolymers with high molar masses and narrow polydispersity. The characteristics and dimensions of isolated (PCEVE-g-PS)-b-(POHEVE-g-PEO) macromolecules were studied by light scattering in THF, a good solvent of both PS and PEO branches, as well as using AFM imaging of highly diluted deposits. Unimolecular rodlike nano-objects with distinct PS and PEO domains were observed, in agreement with their diblocklike structure. In relation with their amphiphilic nature, the combs can self-assemble in different morphologies. When graphite deposits are made from more concentrated methylene dichloride solutions, the PScomb-b-PEOcomb copolymers self-assemble directly on the substrate, forming flowerlike molecular aggregates interconnected by their PEO moieties. When deposits are made from a selective solvent (methanol) of the PEO comb block, hyperbranched micelles formed in the solution retain their structure on the solid substrate, yielding well-defined spherical objects

Application of living ionic polymerizations to the design of AB-type comb-like copolymers of various topologies and organizations

Living anionic and cationic polymerizations have been combined to prepare various types of comb-like copolymers composed of polystyrene (PS) and polyisoprene (PI) blocks, with a precisely controlled architecture. According to the relative placement of these elementary building blocks, combs with randomly distributed PS and PI or with poly(styrene-b-isoprene) diblock branches (I & II, respectively) can be prepared. The reaction procedure initially includes the synthesis of a poly(chloroethylvinyl ether) using living cationic polymerization, which is used as the reactive backbone to successively graft PS-Li+ and PI-Li+ or PI-b-PS-Li+ to obtain structures (I) or (II). The synthesis of Janus-type PS-comb-b-PI-combs (III) initially involves the synthesis of a diblock backbone using living cationic polymerization, which bears two distinct reactive functions having either a protected or activated form. Living PS-Li+ and PI-Li+ are then grafted, in two separate steps, onto each of the reactive functions of the backbone, respectively