Poly(fluoroacrylate)s with tunable surface hydrophobicity via radical copolymerization of 2,2,2-trifluoroethyl α-fluoroacrylate and 2-(trifluoromethyl)acrylic acid

International audienceThe synthesis of poly(fluoroacrylate)s with tunable wettability and improved adhesion for potential applicationas functional coatings was achieved via radical copolymerization of 2,2,2-trifluoroethylα-fluoroacrylate (FATRIFE) with 2-(trifluoromethyl)acrylic acid (MAF), an adhesion-promoting monomer.These copolymerizations, initiated by tert-butyl peroxypivalate at varying comonomer feed ([FATRIFE]0/[MAF]0) ratios led to a series of poly(FATRIFE-co-MAF) copolymers with different molar compositions infair to good conversions (32–87%) depending on the MAF feed content. The microstructures of the synthesizedpoly(FATRIFE-co-MAF) copolymers were determined by 19F NMR spectroscopy. Even at MAFfeed contents higher than 50%, MAF incorporation into the copolymers was lower than 50%, since MAFdoes not undergo any homopolymerization under radical polymerization conditions. The reactivity ratiosof the (FATRIFE; MAF) monomer pair were also determined (rFATRIFE = 1.65 ± 0.07 and rMAF = 0 at 56 °C)evidencing the formation of statistical copolymers. Initiation involving a highly branched perfluorinatedradical that released a •CF3 radical enabled the demonstration of the regioselective attack of the latterradical onto the CH2 of FATRIFE. The resulting poly(FATRIFE-co-MAF) copolymers exhibited various glasstransition temperatures (Tgs) depending on their compositions. Tg values increased with increasing MAFcontents in the copolymer. In addition, their thermal stability (the temperature for 10% weight loss in air,Td10%) increased with increasing FATRIFE content in the copolymer and reached 348 °C (for that containing93 mol% FATRIFE). Finally, a high copolymer MAF content led to both a good adhesion onto metalsubstrates and to improved hydrophilicity, as revealed by the decrease of the water contact angle from107° (for a reference PFATRIFE homopolymer) to 81° (for a copolymer containing 42 mol% MAF)

Micromechanics of root development in soil

International audienc

Analysis of root growth from a phenotyping data set using a density-based model

Major research efforts are targeting the improved performance of root systems for more efficient use of water and nutrients by crops. However, characterizing root system architecture (RSA) is challenging, because roots are difficult objects to observe and analyse. A model-based analysis of RSA traits from phenotyping image data is presented. The model can successfully back-calculate growth parameters without the need to measure individual roots. The mathematical model uses partial differential equations to describe root system development. Methods based on kernel estimators were used to quantify root density distributions from experimental image data, and different optimization approaches to parameterize the model were tested. The model was tested on root images of a set of 89 Brassica rapa L. individuals of the same genotype grown for 14 d after sowing on blue filter paper. Optimized root growth parameters enabled the final (modelled) length of the main root axes to be matched within 1% of their mean values observed in experiments. Parameterized values for elongation rates were within ±4% of the values measured directly on images. Future work should investigate the time dependency of growth parameters using time-lapse image data. The approach is a potentially powerful quantitative technique for identifying crop genotypes with more efficient root systems, using (even incomplete) data from high-throughput phenotyping systems

End-User Modelling

National audienceno abstrac

La chimie extraordinaire de Jules Verne

Tout le monde a en tête les noms des grands romans de Jules Verne qui ont marqué notre enfance et que nous rappelle de temps en temps le passage devant une librairie où trônent ces magnifiques cartonnages rouges de la collection Hetzel. En allant puiser dans son imagination et dans la science de son époque de quoi surprendre et faire rêver ses lecteurs, il est pour beaucoup le fondateur du roman d’anticipation et le créateur de la science-fiction. On ne s’en souvient peut-être plus, mais Jules Verne a aussi truffé ses romans de chimie et celle-ci occupe une place relativement importante dans son œuvre.La célébration en 2005 du centenaire de la mort de l’auteur a été l’occasion pour la communauté scientifique de se replonger dans l’extraordinaire œuvre de l’un des auteurs les plus lus et les plus traduits dans le monde

La chimie extraordinaire de Jules Verne

International audienceTout le monde a en tête les noms des grands romans de Jules Verne qui ont marqué notre enfance et que nous rappelle de temps en temps le passage devant une librairie où trônent ces magnifiques cartonnages rouges de la collection Hetzel. En allant puiser dans son imagination et dans la science de son époque de quoi surprendre et faire rêver ses lecteurs, il est pour beaucoup le fondateur du roman d’anticipation et le créateur de la science-fiction. On ne s’en souvient peut-être plus, mais Jules Verne a aussi truffé ses romans de chimie et celle-ci occupe une place relativement importante dans son œuvre.La célébration en 2005 du centenaire de la mort de l’auteur a été l’occasion pour la communauté scientifique de se replonger dans l’extraordinaire œuvre de l’un des auteurs les plus lus et les plus traduits dans le monde

Experimental study of X-ray photon-induced desorption from molecular ices: indirect mechanism and astrophysical implications

International audienceThe most recent observations of small organic species in the gas phase of the coldest regions of space imply the existence of efficient non-thermal desorption phenomena, central to maintain a sufficient budget of molecules in the gas which should otherwise be depleted by freezing out on interstellar dust grains. This last decade, laboratory experiments have mainly focused on the desorption induced by vacuum UV photons, cosmic rays and recombinative chemistry. However, processes induced by photons of higher energy, despite being present in star and planet formation regions, were largely unknown and neglected in models, until recently. Indeed, X-ray induced desorption from molecular ices has received a peculiar attention in th e past few years 4,5,6. This process, also known as X-ray photodesorption, should participate to the physical and chemical evolution of different astrophysical environments where the X-ray field is important, such as protoplanetary disks, comets and icy moons and planets 7. Recent investigations 1,2,3 have revealed, in the soft X-ray range, an indirect desorption process that induces the desorption of molecules at photon energy where they are not expected to desorb. This indirect mechanism has major implications and still needs to be fully understood. In this context, X-ray photodesorption experiments were conducted at the SOLEIL synchrotron facility in France by coupling the Ultrahigh Vacuum SPICES setup to the SEXTANTS beamline, in order to measure desorption yields by mass spectrometry, but also to shed light on the involved mechanisms. Desorption of simple molecules such as 13 CO and 15 N2 was studied as a simple case in order to characterize the indirect desorption process. Resonant 1s core excitation near the N (~400 eV) or O (~500 eV) K-edge, reachable thanks to tunable and high spectral resolution X-rays from the synchrotron beamline, allows to selectively photo-excite 15 N2 or 13 CO to trigger desorption from ices containing these molecules. This first set of experiments allows to discuss the desorption mechanisms and their properties with respect to the energy transport in the ice. Finally, X-ray photodesorption is studied for methanol CH3OH and other small organic molecules in order to explore the desorption process for more complex molecules, especially relevant for astrochemistry