Why Zeno’s Paradoxes of Motion are Actually About Immobility

International audienceZeno’s paradoxes of motion, allegedly denying motion, have been conceived to reinforce the Parmenidean vision of an immutable world. The aim of this article is to demonstrate that these famous logical paradoxes should be seen instead as paradoxes of immobility. From this new point of view, motion is therefore no longer logically problematic, while immobility is. This is convenient since it is easy to conceive that immobility can actually conceal motion, and thus the proposition “immobility is mere illusion of the senses” is much more credible than the reverse thesis supported by Parmenides. Moreover, this proposition is also supported by modern depiction of material bodies: the existence of a ceaseless random motion of atoms—the ‘thermal agitation’—in the scope of contemporary atomic theory, can offer a rational explanation of this ‘illusion of immobility’. Our new approach to Zeno’s paradoxes therefore leads to presenting the novel concept of ‘impermobility’, which we think is a more adequate description of physical reality

Synthèse d'agents de contrôle originaux our l'obtention de copolymères a-fontionnels par le procédé Raft (application à l'élaboration de particules à chevelure contrôlée)

Le procédé RAFT (transfert de chaîne réversible par addition-fragmentation) est une technique de polymérisation radicalaire contrôlée de choix permettant d obtenir directement des chaînes polymères a-fonctionnelles de longueur contrôlée. La synthèse préalable d agents de transfert de chaîne (ATC) fonctionnalisés est une étape primordiale dans cette optique. Dans ce travail de thèse, une stratégie simple a été développée pour la synthèse d ATC fonctionnalisés utilisant des ATC précurseurs originaux appartenant à la famille des dithioesters. Cette nouvelle voie de synthèse a préalablement été validée à l aide d un composé modèle avant d être appliquée à la synthèse de dithioesters portant un ligand biologique tel que la biotine, un phospholipide ou un dérivé carbohydrate. La polymérisation de type RAFT de la N-acryloylmorpholine en présence de chacun de ces nouveaux bio-ATC vérifie tous les critères d une polymérisation contrôlée. En particulier, les polymères obtenus ont une distribution des masses molaires très étroite (Ip<1,1). De plus, la présence du ligand biologique en extrémité a des chaînes a été confirmée par RMN 1H et par spectrométrie de masse MALDI-ToF.Enfin, cette stratégie de synthèse de polymères a-bio-fonctionnels a été utilisée pour la conception de structures macromoléculaires répondant aux critères requis pour des applications dans le diagnostic biologique : 1- un copolymère réactif de masse molaire élevée précurseur de sondes de détection super-fluorescentes a été synthétisé à partir du dithioester-biotine ; 2- Un procédé de polymérisation mixte associant le principe de la polymérisation en dispersion avec celui de la polymérisation de type RAFT a été imaginé. L utilisation, dans ce procédé, de polymères a-fonctionnels synthétisés à partir du dithioester-sucre a permis l élaboration de particules fonctionnalisées à chevelure contrôlée potentiellement utilisables pour la capture d agents pathogènesa-functionalized polymer of controlled chain length can be designed by the use of the RAFT (Reversible Addition Fragmentation chain Transfer) process, which is a controlled radical polymerization technique. The first requirement for this strategy is to synthesize functionalized chain transfer agents (CTA). In this research work, a simple strategy is presented: original dithioester precursors CTA were designed and used to provide a large variety of functionalized dithioesters. The efficiency of this strategy was previously checked with a model compound, and was then applied to the synthesis of dithioesters bearing biomolecules (bio-CTA) like a biotin, a phospholipid or a carbohydrate derivative. RAFT polymerization of N-acryloylmorpholine mediated by each of these new bio-CTAs is well controlled, the resulting polymer exhibiting narrow molar mass distributions (PDI<1.1). Moreover, 1H NMR and MALDI-ToF mass spectrometry analyses confirmed the presence of the biological compound at the a-end of the chains.Finally, the same strategy (leading to a-bio-functionalized polymers) was used to elaborate macromolecular structures for applications in biological diagnostic tests: 1- a high molecular weight reactive random copolymer was synthesized from the biotin-dithioester, and may serve as highly-fluorescent detection probes; 2 - Functionalized particles with controlled hair were obtained via dispersion polymerization using a-functionalized polymer chains bearing a carbohydrate derivative (potentially able to capture pathogenic agents) as precursor stabilizerLYON1-BU.Sciences (692662101) / SudocSudocFranceF

Asymmetric neutral, cationic and anionic PEO-based double-hydrophilic block copolymers (DHBCs): Synthesis and reversible micellization triggered by temperature or pH

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Thermosensitive and drug-loaded ordered mesoporous silica: a direct and effective synthesis using PEO-b-PNIPAM block copolymers

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Synthesis of Lipid-α-End-Functionalized Chains by RAFT Polymerization. Stabilization of Lipid/Polymer Particle Assemblies

International audienceA functional dithioester including a phospholipid moiety (Lipid-DT) has been synthesized in a high yield (71% after purification) from a precursor chain transfer agent (CTA) and fully characterized. The RAFT polymerization of an acrylamide derivative, N-acryloylmorpholine (NAM), mediated by this Lipid-DT exhibits a prolonged induction period in comparison with a nonfunctional dithioester. This phenomenon is discussed in terms of steric shielding induced by the bulky lipid moiety of the CTA. Moreover, the lipid moiety located at the α-end of the chains has a strong influence on the size exclusion chromatography analyses in THF using a standard-based calibration, with the suspicion of a retention phenomenon. The well-defined structure of the lipid-end-functionalized polymer chains has been evidenced by MALDI−TOF mass spectrometry. Finally, these chains have been successfully incorporated into lipid/polymer particle assemblies (LipoParticles) that resulted in an improved stabilization in aqueous medium at relatively high ionic strength (300 mM)

Hierarchically porous Pd/SiO2 catalyst by combination of miniemulsion polymerisation and sol-gel method for the direct synthesis of H2O2

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Polyelectrolyte/fluorinated polymer interpenetrating polymer networks as fuel cell membrane

International audienceOriginal membranes based on an interpenetrating polymer network (IPN) architecture combining a poly(2-acrylamido-2-methyl-1-propane sulfonic acid) (AMPS) network and a fluorinated network were synthesized. The AMPS weight compositions were varied from 50 to 70 wt%. The first network was achieved by radical copolymerization of AMPS with a fluorinated telechelic diacrylate while the second one was obtained by photoinitiated cationic copolymerization of telechelic fluorinated diepoxide with trimethylol propane triglycidyl ether. The morphologies of these different IPNs were deduced from small-angle X-ray scattering (SAXS) spectra and dynamic thermomechanical analysis (DMTA). The main functional properties related to their use as proton exchange membrane in fuel cells were quantified, such as water vapor sorption, liquid water uptake (22-59 wt%), proton conductivity (1-63 mS/cm), gas permeability (0.06 and 0.80 barrer for dry oxygen and hydrogen, respectively), and oxidative and thermal stabilities. More precisely, the effects of the ionic exchange capacity (IEC) varying from 1.73 to 2.43 meq/g and the cross-linking density of the conducting phase on the morphology and the properties of IPN membranes were studied in detail. Finally, these IPN membranes were tested as fuel cell membrane and a correlation between the ex-situ and in-situ characterizations was established