Bruno A.,National Graduate School of Chemistry, Montpellier
Macromolecules | Year: 2010
Controlled radical polymerizations (CRP) were pioneered in the late 1970s. Since then, tremendous investigations have been developed, especially from mid-1990s which generated much enthusiasm on CRP. However, the extraordinary scientific development of CRP contrasts with the limited number of commercially available products derived from these technologies. But, for fluoropolymers, the situation is different since iodine transfer polymerization of fluoroalkenes led to commercially available thermoplastic elastomers as soon as 1984. A browse or CRP of fluorinated monomers is presented and is classified into three families: (i) the CRP of fluorine-containing styrenic monomers mainly occur from nitroxide-mediated polymerization (NMP) or by atom radical transfer polymerization (ATRP); (ii) that of fluorinated (meth)acrylic monomers from NMP, ATRP, and in the presence of iniferters; and finally (iii) fluoroalkenes (which is a real challenge since these monomers are gaseous) can be (co)polymerized by iodine transfer polymerization or by processes that required either borinates or xanthates (MADIX). A peculiar interest lies in the CR copolymerization of fluoroalkenes with other comonomers (such as vinylidene fluoride, chlorotrifluoroethylene, 3,3,3-trifluoropropene, hexafluoropropylene, perfluoromethyl vinyl ether, or α-trifluoromethacrylic acid) in the presence of either xanthates, borinates, or iodo compounds. These technologies enable one to generate copolymers that exhibit well-defined architectures, such as telechelic, block, and graft copolymers. Merits and limitations of CRP of F-monomers are also reported. Finally, this Perspective is illustrated by several properties and applications of these fluorinated copolymers (such as surfactants, thermoplastic elastomers, fuel cell and ultrafiltration membranes, dielectrical polymers, optical storage devices, or polycondensates, the fluorinated segments of which bring softness and thermal stability). Hence, CRP can be regarded as a revolutionary method to produce precisely controlled, next-generation specialty fluorinated (co)polymers. © 2010 American Chemical Society.
Dondoni A.,University of Ferrara |
Marra A.,National Graduate School of Chemistry, Montpellier
European Journal of Organic Chemistry | Year: 2014
Alkyne hydrothiolation - that is, the addition of the SH bond of a thiol across the carbon-carbon triple bond of an unactivated alkyne - belongs to the ample class of hydrofunctionalization reactions whose main feature is their occurrence with total atom economy. Hence this reaction is emerging as a valuable tool for the preparation of sulfur-containing compounds such as vinyl thioethers, which are of interest for their own biological properties and for their use as intermediates in total synthesis. Thus, the first part of this review deals with the various efforts directed towards the preparation of vinyl thioethers in a regio- and diastereoselective manner by metal-catalyzed approaches in recent years. The number of methods employed, with use of a variety of catalysts and reaction conditions, allow the synthesis of vinyl thioethers to be carried out with high efficiency and selectivity. The second part of the article is based on the use of the photoinduced free-radical approach to hydrothiolation, which allows the introduction of two thiol fragments across the carbon-carbon triple bond, thereby leading to the formation of dithioethers. This approach turned out to be especially useful as a ligation tool for the installation of densely functionalized arrays on various scaffolds and complex biomolecular systems. Concluding remarks emphasize the role of the photoinduced free-radical strategy as a complementary tool to copper-catalyzed azide-alkyne cycloaddition. Metal-catalyzed approaches for the selective preparation of vinyl thioethers (top) and free-radical approaches for the assembly of multifunctionalized constructions (bottom) are surveyed. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Engel A.B.,National Graduate School of Chemistry, Montpellier
Nanotechnology | Year: 2013
New nanostructured electrodes, promising for the production of clean and renewable energy in biofuel cells, were developed with success. For this purpose, carbon nanofibers were produced by the electrospinning of polyacrylonitrile solution followed by convenient thermal treatments (stabilization followed by carbonization at 1000, 1200 and 1400° C), and carbon nanotubes were adsorbed on the surfaces of the fibers by a dipping method. The morphology of the developed electrodes was characterized by several techniques (SEM, Raman spectroscopy, electrical conductivity measurement). The electrochemical properties were evaluated through cyclic voltammetry, where the influence of the carbonization temperature of the fibers and the beneficial contribution of the carbon nanotubes were observed through the reversibility and size of the redox peaks of K3Fe(CN)6 versus Ag/AgCl. Subsequently, redox enzymes were immobilized on the electrodes and the electroreduction of oxygen to water was realized as a test of their efficiency as biocathodes. Due to the fibrous and porous structure of these new electrodes, and to the fact that carbon nanotubes may have the ability to promote electron transfer reactions of redox biomolecules, the new electrodes developed were capable of producing higher current densities than an electrode composed only of electrospun carbon fibers.
Derichter R.K.,National Graduate School of Chemistry, Montpellier |
Ming T.,Huazhong University of Science and Technology |
Caillol S.,National Graduate School of Chemistry, Montpellier
Renewable and Sustainable Energy Reviews | Year: 2013
Over the last decades, fighting global warming has become the most important challenge humanity has to face. Therefore technologies of carbon dioxide capture, sequestration and recycling are equally important in order to tackle the global climate change stakes. Among recycling technologies, photocatalytic processes reducing CO2 with H2O back to fuels or to other useful organic compounds, have the potential to be part of a renewable energy system. Indeed these processes can help to control CO 2 emissions and eventually eliminate CO2 in excess. This perspective paper describes a large size device, able simultaneously: • to proceed to direct air capture (DAC) of CO2; • to transform part of it into useful chemicals, like hydrocarbons or syngas; • and to produce renewable energy, thus preventing future CO2 emissions. Synergies between solar chimney power plants (SCPPs) and semiconductor photocatalysis in order to create giant photocatalytic reactors for artificial photosynthesis are discussed, as well as scale economies for unconventional carbon capture directly from the atmosphere. This paper presents a carbon negative emission technology obtained by coupling SCPPs with DAC systems which allows many scale economies, and also synergies to proceed to solar-to-chemical energy-conversion process by photocatalytic reduction of atmospheric CO2 under sunlight. © 2012 Elsevier Ltd.
Auvergne R.,National Graduate School of Chemistry, Montpellier |
Caillol S.,National Graduate School of Chemistry, Montpellier |
David G.,National Graduate School of Chemistry, Montpellier |
Boutevin B.,National Graduate School of Chemistry, Montpellier |
And 2 more authors.
Chemical Reviews | Year: 2014
The works undertaken to obtain either partially or fully biobased epoxide materials are studied. The reaction between the phenate ion and ECH 2 reveals two competitive mechanisms, one-step nucleophilic substitution with cleavage of the C-Cl bond and a two-step mechanism based on ring opening of ECH (2) with ArO- (1') followed by intramolecular cyclization (SNi) of the corresponding alcoholate, containing one atom of chlorine in the β-position, formed in situ. Depending on the substituent position or nature in the phenol, it takes 6-20 h at reflux or 24-26 h at room temperature to complete the reaction. The reaction of ECH with an alcohol is more difficult, with many side reactions, since this reaction generates new alcohol groups with similar pKa values which are able to react with the epoxy group of ECH, thus leading to its homopolymerization. Epoxies are able to react with (meth)acrylic acid to give formulations for coating applications or vinyl ester monomers and networks after radical polymerization.