Search

Bismuth vanadate (BiVO4) has surface states that give rise to defect levels that mediate electron-hole recombination. In order to minimize the inefficiencies, an ultrathin Al overlayer was deposited on the BiVO4electrodes. A 54 % improvement on the photocurrent density was obtained using the Al-modified BiVO4electrode, accompanied by a 15 % increase in stability over 7.5 h of continuous irradiation. Moreover, surface capacitance measurements showed that the Al overlayer was indeed passivating the surface states. We also shed light on the deposition of an Al overlayer on the surface of BiVO4, by investigating the process on model BiVO4powders. This study presents useful, previously unreported information about the surface chemistry of BiVO4based on experimental methods and gives unique insights on the characterization of the BiVO4surface. The existence of surface reactive sites on BiVO4was confirmed and quantified (1.5 reactive sites/nm2) via chemical titration

International audience; The very first step of almost any separation process design procedure is the thermodynamic feasibility analysis. In the case of distillation, residue curve maps (RCMs) represent an essential tool to assess whether the separation is feasible or not. However, the analysis is generally carried out by referring to nominal operating conditions and product purities as specification. This means that, when process parameters are likely to undergo fluctuations, the prediction of the system response is not that obvious. An ABE/W (acetone−butanol−ethanol/water) mixture was then selected as a case study since it allows us to discuss several non-ideal thermodynamic behaviors and because of the renewed interest in biorefinery and sustainable processes during recent years. Residue curve mapping was then exploited to determine the thermodynamic feasibility range for multicomponent distillation processes as well as for distillation trains and process-intensified solutions taking into account both product purity and product recovery specifications. The final product of this study is a thorough procedure to determine the flexibility boundaries of feed and product compositions as well as an immediate and intuitive graphical representation from a binary standard distillation column to a complex multicomponent dividing wall column application

International audience; Maleimides are attractive systems for photopolymerize for two major reasons: (1) they follow a radical mechanism without requiring a photoinitiator and (2) their rate of polymerization corresponds similarly to acrylates, which are commonplace in the industry. In this work, bismaleimide polypropylene oxide was cured under UV light forming thin films. Their surface properties were modified by copolymerization them with fluorinated comonomers. To this goal, perfluoropolyalkylethers (PFPAEs) with maleimide groups were synthesized, varying their chain structure, their functionality degree and consequently their intrinsic viscosity. These PFPPAE comonomers were highlighted to segregate at the surface, assuring omniphobic properties and acting as a protective layer against oxygen inhibition. These phenomenon were observed even when added at a concentration ≤5% w/w with respect to the main polypropylene oxide monomer. XPS analyses confirmed the segregation of the fluorine atoms at the surface during the UV-curing process of the coatings.

International audience; Carbon Nitride and its polymorphs have recently gained large interests for their huge properties and applications in different fields, from lighting to photocatalysis. Further, several attempts were recently devoted to tune and control its optical and electrical properties. In this report we analyze phenyl modified Carbon Nitride structures obtained by simple thermal polymerization at different temperatures (250-400°C) of the starting precursor: 2,4-diamino-6-phenyl-1,3,5-triazine. A multi-technique experimental data (XRD patterns, Raman, TGA and DTG, steady-time and time resolved Luminescence, Photoluminescence Excitation spectra, Reflectivity spectra) was applied to analyze the relationship between structural and optical properties and to give more insight on the effect of synthesis procedure on the final polymer. The optical properties evidenced an interesting shift towards the visible region of the absorption spectrum of the phenyl modified g-C 3 N 4 polymer that, associated with the high optical quantum yield (about 60%) and to a broad emission in the green-red spectral region, makes the samples very suitable for lighting applications. Indeed, we report a first prototype of white LED emission by assembly of a commercial blue LED and the Phenyl modified g-C 3 N 4 powders as phosphor, verifying the structural and optical stability over about 10,000 working hours.

International audience

Perfluoropolyalkylether (PFPAE) reactive macromers can be used in very low concentration (≤2 wt%) as efficient surface modifying agents of epoxy resins to obtain hydrophobic photocured copolymers. However, the hydrophobicity achieved thanks to the spontaneous migration of the PFPAE chains to the free surface could be dramatically lost due to environmentally induced rearrangements of the fluorinated segments, even though they are chemically bonded to the polymer matrix. To preserve the coating performances of the photocured copolymers when exposed to various environments, different approaches have been investigated. In particular, to hinder the mobility of the fluorinated chains, the length of the fluorinated comonomer chain, the epoxy matrix stiffness, and the functional PFPAE end-groups have been tuned. Such strategies are demonstrated to inhibit or completely suppress the surface reconstruction of the copolymers when exposed to different surrounding environments (e.g., immersion in water or oil), allowing to obtain photocured films with a long-term and constant reduced surface energy of ≈20 mN/m.

The use of biobased monomers in emulsion polymerization arises as an attractive option for the synthesis of green polymers. Eugenol, a naturally occurring phenol that is currently mainly produced from clove oil but could also be obtained by depolymerization of lignin, is an interesting molecule for the preparation of biobased monomers and polymers. Readily polymerizable functional groups can be easily introduced into its chemical structure through modification of the phenol group. In the present work, eugenol-based methacrylates have been used as monomers in emulsion radical polymerization with different initiation systems. Stable latexes of poly(ethoxy dihydroeugenyl methacrylate), poly(ethoxy eugenyl methacrylate) and poly(ethoxy isoeugenyl methacrylate) with particle diameter size in the 45–71 nm range were successfully obtained. Glass transition temperatures of the resulting polymers ranged between 20 and 72 °C. This study opens the way to the use of these new biobased monomers into latexes formulatio...

International audience; Eugenol, a natural phenol currently mainly obtained from clove oil, is an interesting aromatic building block for the synthesis of novel biobased monomers. It can also be obtained from lignin depolymerization, becoming a promising building block due to lignin availability as biomass feedstock. The synthesis of eight monomers derived from eugenol containing polymerizable functional groups is achieved. The (meth)acrylation of eugenol, isoeugenol, and dihydroeugenol is performed and the solution homopolymerization of these biobased monomers is studied. Moreover, aiming to prepare functional polymers, the introduction of epoxy and cyclic carbonate groups is executed via modification of the allylic double bond present in eugenol derived methacrylate. Thus, a novel platform of versatile biobased monomers derived from eugenol is presented, opening the opportunity to use them in a wide range of polymerization processes and applications

Semi-interpenetrating polymer networks (semi-IPNs) were obtained by the cationic photoinduced polymerization of a hydrogenated difunctional vinyl ether (DVE3) and a fluorinated monofunctional vinyl ether (FVE). By analyzing the kinetics of polymerization and the thermal properties of the crosslinked networks, it was demonstrated that the molecular architecture of the photopolymers could be tuned by varying the amount of the fluorinated additive. When the weight content of FVE exceeded 15 wt.%, the monofunctional fluorinated monomer homopolymerized forming linear chains that were dispersed in the hydrogenated matrix composed by the DVE3 crosslinked network, thus generating a semi-IPN structure. Both bulk and surface properties of the resulting photopolymers were influenced by the addition of the fluorinated product. Fluorinated semi-IPNs were biphasic, displayed good thermal resistance both in air and under nitrogen (T 10 > 200 °C, T 50 > 380 °C) and showed a surface energy as low as 26 mN m −1 .

International audience; α,β-unsaturated esters are usually synthesized for polymer applications. However, the addition of maleate (cis-configuration) to a fluorinated moiety is challenging due to its potential isomerization during esterification. Various synthetic routes were attempted and led to very low conversion or side-products. The immiscibility of both reagents combined with an easy isomerization or attack on the double bond were potential explanations. In this paper, the synthesis of maleates oligo(hexafluoropropylene oxide) is reported by Steglich esterification and the reaction conditions are discussed depending on the molecular weight of the fluorinated moieties. After UV-curing, hydrophobic polymers were obtained by copolymerization with vinyl ethers by electron acceptor–donor systems.

International audience; Free organic solvent ink containing graphite, carboxymethyl cellulose and microfibrillated cellulose as active material, dispersing and binder, respectively, has been formulated to produce flexible and eco-sustainable electrodes for lithium ion batteries. Content ratio of components and dispersion protocol were tailored in order to have rheological properties suitable for a large and cheap manufacturing process as well as screen printing. The bio-sourced printed electrodes exhibit a high porosity value of 70% that limits the electrochemical performances. However, the calendering process enhances electrode performances by increasing the reversible capacity from 85 until 315 mAh/g and reducing porosity to an optimal value of 34%. Moreover the introduction of 2% w/w of monofluoro-ethylene carbonate in the electrolyte reduced their reversible capacity loss of 11% in the printed electrode.

International audience; An investigation into the in situ preparation of polymer/silver nanoprism composites is described. Photoinitiated polymerizations of N-vinyl pyrrolidone (NVP) in water using 2-hydroxy-2-methyl-1-phenyl propanone as photoinitiator under nitrogen and simultaneous redox reactions of AgNO3 resulted in the formation of poly(N-vinyl pyrrolidone) (PNVP)/silver nanocomposites. Prolonged irradiations at low photoinitiator concentration and equimolar concentrations of AgNO3 and NVP produced only spherical silver nanoparticles. The nanocomposites produced at high silver and photoiniatiator concentrations with short irradiation times e.g. 5 min contain polygonal (mainly triangular) silver nanoprisms as evidenced by spectral and TEM analysis.

International audience; Fluorinated hydroxytelechelic polybutadiene (PBF), which is synthesized from the radical addition of a fluorinated mercaptan onto a hydroxytelechelic polybutadiene was used as an efficient surface and mechanical modifier in original formulations to enable the UV cationic polymerization of a telechelic diepoxy cycloaliphatic resin, leading to crosslinked films. Various amounts of PBF were used (ranging between 0 and 15 wt %). The kinetics of photocrosslinking revealed that the diepoxyde conversion reached 70% only in the absence of PBF, whereas it was about 90% in the presence of 10 wt % of PBF. When the PBF content increased, the dynamic mechanical measurements showed that: (i) the glass transition temperature values decreased and (ii) the resilience increased. The hydrophobicity of these films was investigated from the water contact angle (WCA) values showing a surface modification of the poxy-based system. Indeed, great modifications were noted on the extreme surface (i.e., air side) of the films (with WCA values as high as 120°) in contrast to those observed on the substrate side.

The I2 adsorption in Ni(pz)[Ni(CN)4] clathrate was investigated by combining spectroscopic and computational tools, including electrical measurements, solid UV–vis, infrared, and Raman spectroscopy, and Monte Carlo simulations. We observed that while ionic I3– species are formed at low I2 concentration, iodine in its molecular form is present at higher concentration. The appearance of polyiodides was suggested to result from the interactions between the guest and the [Ni(CN)4]2– moieties of the host framework.

International audience; Within the framework of high-temperature polymer fuel cells doped with phosphoric acid, we investigate the replacement of the conventional binder in the catalyst layers by functionalized solid PVDF nanospheres. Aim of this study is to develop and test an innovative binder which might create enhanced electrode porosity and acid distribution. Aqueous suspensions of PVDF nanospheres (d ~ 200 nm) are obtained by radical emulsion polymerization and are functionalized by Vinyl-Imidazole (VI) groups via in situ g-radiation. As a consequence the nanospheres can interact with H3PO4 to obtain proton conductivity. Catalyst inks are prepared mixing the nanospheres with commercial Pt/C electrocatalyst powder, solvents and phosphoric acid. Prototype electrodes are deposited by spraying and preliminary fuel cell tests are carried out at 160 C under dry H2/air. Electrodes with grafted PVDF nanospheres as solid binder are demonstrated and its understanding is in progress. Further improvements are outlined.

A series of thermally stable Hofmann-type clathrate structures with the general formula M(pz)[M'(CN)4], where M and M' are bivalent metal ions M(II) = Ni(II), Co(II), M(II)' = Ni(II), Pd(II), Pt(II), and pz is the pyrazine bidentate ligand, was synthesized and investigated for the efficient entrapment of iodine (I2) in solution and in the gas phase. Iodine-containing clathrates thus prepared were analysed to determine the saturation capacity, thermal stability, guest-induced structural changes of the clathrate's lattice and the nature of the confined iodine according to the chemical composition of the host structure. An efficient confinement of about 1 I2 per unit cell is observed for the series of clathrates with the Ni(II) and Pd(II) ions in the square planar position whatever the bivalent metal ion in the octahedral position. Specific responses in the lattice adjustment are detected for Co(II) in the octahedral and Pd(II) in the square planar positions.

Hybrid nanocomposites based on nanoparticles with the Hofmann-type structure NiII(pz)[NiII(CN)4] (where pz = pyrazine) confined into mesoporous silica or porous glass pearls were synthesised by sequential coordination of the molecular precursors into the pores of the functionalized matrices. Infrared (IR) and UV/Visible (UV-Vis) spectroscopy, powder X-ray diffraction (PXRD), and transmission electron microscopy (TEM) reveal the presence of uniformly-sized spherical NiII(pz)[NiII(CN)4] nanoparticles of 3–6 nm, which are homogeneously dispersed into the matrices. These nanocomposites are able to efficiently capture iodine from cyclohexane solutions with a maximum sorption capacity of 1.75 mmol per g of material. A particular emphasis is given on the mechanism of iodine sorption as well as on the sorption cycling ability of the materials.

International audience; The effect of post-synthesis hydrothermal treatments on MCM-48 has been studied by 29Si MAS-NMR and IR spectroscopies, X-ray diffraction, thermal gravimetry, and gas volumetry. Special attention has been given to the characterisation of the precursors before calcination and a method to evaluate the pore opening of MCM-48 from diffraction and volumetric data is given. The hydrothermal treatment does not affect the organisation of the cetyltrimethylammonium mesophase but extracts a fraction of the surfactant and increases the thickness of the silica wall. The lower area of the silica-surfactant interface after hydrothermal treatment brings about an improved stability of MCM-48 during calcination and allows the pore size of the precursor to be preserved in the calcined solid. After calcination, the hydrothermally treated samples are less prone to rehydrate and, as a consequence, their stability upon storage in moist atmosphere is dramatically improved.

Ultrasound is employed to functionalize the surface of porous silicon microparticles at room temperature with unsaturated organic compounds, with no need for heating or for UV treatment.

In this paper, a new theory allowed calculating the pyroelectric coefficient “p” using the diffusion of a thermal wave within materials having a pyroelectric effect. The demonstration is performed on materials composed by various percentages of a cycloaliphatic epoxy (CE) resin and of a flexibilizing comonomer (1,6-hexanediol diglycidyl ether — HDGE). By using an electric field measurement technique (the Thermal Step Method — TSM), the signal obtained on these materials (a current) presents an atypical form, which requires the modification of the theoretical model of the TSM. Indeed, the theory of the TSM technique has been initially developed for insulating materials with a high dielectric time constant. An adaptation of the technique is thus necessary to analyze the behavior of materials, which present a modification of their molecular structure during the application of the thermal wave. During a space charge characterization performed on these materials, we have observed an atypical shape for the thermal step currents. To help in the interpretation, the broadband dielectric spectroscopy and the Differential Scanning Calorimetry technique (DSC) were used to obtain additional information. Considering these results, a circuit containing a resistor and a capacitor in series has been used for modeling the materials. This equivalent circuit constitutes the beginning of the new theory, which is developed in this paper. The pyroelectric coefficient generated by the thermal step diffusion, due to the presence of a pyroelectric effect of these studied materials, has been calculated using the detailed model.

This work focuses on the dielectric properties of a UV-cured epoxy network with a low glass transition temperature obtained through photoinduced copolymerization of a cycloaliphatic diepoxy monomer, 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate (CE), with 1,6-hexanediol diglycidyl ether (HDGE). The crosslinking density of the system has been tuned using different amounts of the low glass transition temperature HDGE comonomer (up to 60 wt.% HDGE). The structural morphology and space charge obtained with the Thermal Step Method were studied following various thermal treatments of the samples. Both the thermal properties and the dielectric responses (dielectric constant) for the UV-cured HDGE/CE systems turned out to be dependent on the structural morphology and composition of the polymer network. In particular, two relaxation modes, γ, β and α were observed, attributed to local molecular motions. Lastly, the potential effect of moisture and/or ions and the effect of space charge on the copolymers were also investigated.

A nanostructured porous silicon chip functionalized with dichlorofluorescein is employed as a nanoreactor to respond to Reactive Oxygen Species (ROS) and to real-time studying redox reactions.

International audience

International audience

International audience; By incorporating molecular copper iodide clusters of formula [Cu4I4L4] (L = PPh2(CH2)2CH3) into an UV-polymerizable acrylic resin, namely BEDA (Bisphenol-a-EthoxylateDiAcrylate), transparent and highly emitting photoluminescent composite materials have been synthesized. In these materials, the original luminescence properties of the copper iodide cluster and the transparency and processability of the acrylic matrix are combined. Study of the photopolymerization kinetics shows that the clusters incorporated in low concentration have limited influence on the polymerization reaction leading to a highly cross-linking polymeric matrix. These composite materials exhibit thermochromic luminescence properties with intense emissions varying with the temperature. A perfectly controlled luminescence thermochromism is observed due to a 'protecting effect' of the matrix preventing the non-radiative phenomenon of the cluster luminescence. The patterning of these UV-polymerizable photoluminescent films has been also realized by the UV-NIL technique to optimize the light-emitting properties of these materials. The surface patterning acts as a diffraction grating to extract the light which was previously guided inside the film. Moreover, the nanopatterning allows tuning of the emission color of the film as a function of the viewing angle. These composite materials present potential applications as photoactive systems with emission wavelength sensitive to the temperature and the surface nanostructuration.

The coupling of optical Bloch surface waves at the truncated end of one dimensional porous silicon photonic crystals is exploited for fast vapour sensing. Self-standing multilayered membranes bound to transparent substrates were fabricated by electrochemical etching and used in an attenuated total reflection configuration to resonantly excite the surface waves and perform real-time sensing.

The high stability of Salonen's thermally carbonized porous silicon (TCPSi) has attracted attention for environmental and biochemical sensing applications, where corrosion-induced zero point drift of porous silicon-based sensor elements has historically been a significant problem. Prepared by the high temperature reaction of porous silicon with acetylene gas, the stability of this silicon carbide-like material also poses a challenge--many sensor applications require a functionalized surface, and the low reactivity of TCPSi has limited the ability to chemically modify its surface. This work presents a simple reaction to modify the surface of TCPSi with an alkyl carboxylate. The method involves radical coupling of a dicarboxylic acid (sebacic acid) to the TCPSi surface using a benzoyl peroxide initiator. The grafted carboxylic acid species provides a route for bioconjugate chemical modification, demonstrated in this work by coupling propylamine to the surface carboxylic acid group through the intermediacy of pentafluorophenol and 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride (EDC). The stability of the carbonized porous Si surface, both before and after chemical modification, is tested in phosphate buffered saline solution and found to be superior to either hydrosilylated (with undecylenic acid) or thermally oxidized porous Si surfaces.

International audience

The synthesis of porous silicon-based photonic structures for bio-sensing applications has been widely investigated in the last years. Thanks to its spongiform structure, porous silicon can efficiently host many organic molecules dispersed in solutions having proper chemical affinity. Fluorescent emission of organic-dyes embedded in porous silicon can be enhanced if a photonic structure like a Fabry–Perot resonator is employed as a host solid matrix. In this work we present experimental evidence of a fluorescence enhancement effect obtained by means of doubly resonant microcavities tuned on both the excitation and the emission wavelengths. The use of doubly resonant cavities allows both a resonant excitation of dyes and a resonant amplification of the emission. We demonstrate that small concentrations of fluorescent dyes down to few picomoles can be detected. The bio-sensing capabilities of such a structure are tested on larger molecules of fluorescein-labelled protein A, yielding to an evident lowering of the detection limit by 2 orders of magnitude.

International audience; Transmission FT-IR spectroscopy allowed to monitor the deuteration of wafers of chitosan aerogel and xerogel by D2O vapor at room temperature. The complete deuteration of the alcohol and amine groups of the aerogel (surface area 175 m2 g-1 as measured by N2 volumetry) confirmed the high accessibility of the functional groups of the polymer. The xerogel (surface area 5 m2 g-1) was only partially deuterated in more severe conditions. The isotopic shift of the deuterated groups allowed to confirm or revise some attributions of infrared bands of chitosan.

We describe the use of one-dimensional porous silicon (p-Si) photonic crystals for guiding TE-polarized surface electromagnetic waves (SEWs). Although bulk and interface roughnesses might deteriorate the optical response of photonic structures, we observed reflection spectra presenting narrow (≲6nm) reflectivity anomalies associated with SEWs. In analogy with surface plasmons, SEWs are strongly sensitive to surface modifications. As a proof of principle for a sensor, we provide a direct real-time monitoring of the reversible interactions of organic vapors with the p-Si multilayer. We highlight the higher sensitivity of the SEW-based detection scheme as compared to a method exploiting perturbations of waveguide modes.

International audience; Transmission FT-IR spectroscopy allowed to monitor the deuteration of wafers of chitosan aerogel and xerogel by D2O vapour at room temperature. The complete deuteration of the alcohol and amine groups of the aerogel (surface area 175 m2 g-1 as measured by N2 volumetry) confirmed the high accessibility of its functional groups. The xerogel (surface area 5 m2 g-1) was only partially deuterated in more severe conditions. The isotopic shift of the deuterated groups allowed to confirm or revise some attributions of infrared bands of chitosan.

The acidity of alginate aerogel films has been investigated by infrared spectroscopy of adsorbed NH(3). Supercritical drying of the alginate provided samples with a surface area of several hundred square meters per gram, in which the probe molecule could reach all acidic sites. Free carboxylic groups were studied on acid-gelled alginates and were found to behave as effective Brønsted acid sites. Ionotropic alginate gels formed by alkaline earth cations presented only the Lewis acidity of the cations. Ionotropic gels formed by transition metal cations presented both Lewis and Brønsted sites, because of the presence of a fraction of free carboxylic groups. The incomplete salification was correlated to the pH of the gelling solutions.

International audience; The effect of post-synthesis hydrothermal treatments on MCM-48 has been studied by 29Si MAS-NMR and IR spectroscopies, X-ray diffraction, thermal gravimetry, and gas volumetry. Special attention has been given to the characterisation of the precursors before calcination and a method to evaluate the pore opening of MCM-48 from diffraction and volumetric data is given. The hydrothermal treatment does not affect the organisation of the cetyltrimethylammonium mesophase but extracts a fraction of the surfactant and increases the thickness of the silica wall. The lower area of the silica-surfactant interface after hydrothermal treatment brings about an improved stability of MCM-48 during calcination and allows the pore size of the precursor to be preserved in the calcined solid. After calcination, the hydrothermally treated samples are less prone to rehydrate and, as a consequence, their stability upon storage in moist atmosphere is dramatically improved.

Crystalline samples of Na2M2(BO3)2O ( M = Al , Ga ), Na1.5Ca0.25Ga2(BO3)2O and NaCa0.5Ga2(BO3)2O are prepared by conventional high temperature solid state synthesis technique. Temperature dependent impedance spectroscopy measurements are performed. For Na2Al2(BO3)2O and Na2Ga2(BO3)2O, high and low temperature regimes have to be distinguished. Only one regime is observed for the calcium-substituted samples Na1.5Ca0.25Ga2(BO3)2O and NaCa0.5Ga2(BO3)2O.

session affiche 3 " Capteurs, Instrumentation et techniques de caractérisation " [A03RIV17]; National audience; Nous avons réalisé un guide d'onde planaire enterré en silicium poreux oxydé imprégné de Rouge Congo pour la détection d'espèces acides ou basiques en phase gazeuse. Par spectrométrie UV-Vis, nous montrons que, en présence de vapeurs d'HCl, la bande d'absorption du matériau poreux composite se déplace du bleu au rouge dans le domaine du spectre visible. Ce déplacement est réversible lors de l'exposition à de l'ammoniac. Les premiers résultats sur le comportement du guide composite à 633 nm montrent que la lumière propagée est transmise en présence d'une atmosphère basique et qu'elle est absorbée en présence de vapeurs d'HCl.

symposium N " New materials and technologies in sensor applications ", session I " Materials and characterisations " [N-I.6]; International audience; A method to impregnate OPS by means of a suitable CR solution has been developed, taking into account properties of solvent (e.g. b.p. polarity, etc.) and environmental conditions (e.g. vacuum and heating) in order to enhance and optimise drying and filling of the pores of the material. Presence of CR in depth has been investigated by means of micro-Raman spectroscopy. A good transmittance of the porous layer, before impregnation, has been found by means of spectroscopic measurements in the visible spectral range, in Specular Reflectance mode. An absorption band, centred on about 490 nm, related to the presence of CR inside the pores, appears after impregnation by the dye, whereas that shifts to ~ 650 nm after exposition to acid vapours. The shift is reversible, that is the initial conditions are restored by exposition to basic vapours. This composite material is interesting for achievement of waveguides acting as chemical sensors optically monitored. By this way, bilayers of porous material have been performed for the realisation of planar waveguides. Several porosity values for the guiding layer have been attempted to define the bestconfiguration for the waveguides at 633 nm. After filling with CR, how the light is guided depending on the pH has been studied.

The authors examine six stopping methods of hydration of monocalcium aluminate. The most suitable method seems to be the following: -An ethanol washing; this process is repeated three times; -A further washing with a mixture ethanol-ethyl ether (to be repeated three times); -A drying in stove at 40°C during six hours. // Les auteurs examinent six modes de stoppage de l'hydratation de l'aluminate monocalcique. Le plus approprié semble être le suivant : - un lavage à l'éthanol ; cette opération est répétée trois fois ; - un nouveau lavage avec un mélange éthanol-éther éthylique ; cette opération est également répétée trois fois ; - un séchage dans une étuve à 40°C pendant six heures.

The synthesis of poly(vinylidene fluoride)-graft-oligomeric hexafluoropropylene oxide graft copolymers [poly[VDF-g-oligo(HFPO)-PIPE] is presented, where VDF, HFPO, and PIPE stand for vinylidene fluoride (CH2CF2), hexafluoropropylene oxide (CF3CFCF2O) and, perfluoroisopropenylether (–OC(CF3)CF2), respectively. First, an 82% isolated yield of oligo(HFPO)-PIPE macromonomer was achieved by using oligo(HFPO) primary iodide as the starting reagent. Then, the radical copolymerization of VDF with the PIPE comonomer, initiated by perfluoro-3-ethyl-2,4-dimethyl-3-pentyl persistent radical (PPFR), was studied under various conditions. The PPFR initiator, stable at room temperature, was able to release a ˙CF3 radical starting from 80 °C. The resulting poly[VDF-g-oligo(HFPO)-PIPE] graft copolymers were produced in good isolated yields (76 to 97%). The molar percentages and molar masses of such graft copolymers were assessed by 19F-NMR spectroscopy using the CF3– end-group label. The molar percentages of VDF and oligo(HFPO)-PIPE comonomers reached up to 99% and 20%, respectively, while the molar masses ranged between 7500 and 42 600 g mol−1. Their thermal properties showed: (i) fair to satisfactory thermostability (T5%d) showing up to 271 °C under nitrogen, (ii) glass transition (Tg) ranged from −81 to −82 °C while (iii) their melting temperature (Tm) ranged between 150 and 163 °C. Moreover, the synthesized copolymers were demonstrated to be highly omniphobic (i.e., simultaneously hydrophobic and oleophobic), showing a water contact angle of ca. 133°, a hexadecane contact angle ca. 70°, and a surface energy as low as 12 mN m−1.

The more favourable experimental conditions of cooling and grinding was defined for calcium aluminates obtained by solid-solid reaction with C/A ratio in the range 0.96 – 1.04. The composition of the samples was related to the apparition of different phases : “substoichiometric” solid including CA and CA 2 , with a calcium deficiency “super-stoichiometric” samples including C 12 A 7 with an excess of calcium as well as mixtures of sub and super-stoichiometric solids could be obtained. “Super-stoichiometric” samples presented ionized anionic vacancies. During hydration, “super-stoichiometric” aluminate led to the formation of a first hydrate. The hydration kinetics depended on the ratio C 12 A 7 /CA 2 of the samples.

L'étude du pic calorimétrique associé à l'hydratation isotherme de l'aluminate monocalcique de 1 à 35°C permet de définir les domaines de formation séparée ou simultanée des deux hydrates hexagonaux CaOAl2O310H2O et 2CaOAl2038H20 dont les cinétiques d'apparition sont très différentes. // The study of the calorimetric peak associated with the isothermal hydration reaction of monocalcium aluminates from 1 to 35°C allow us to define the conditions of separate or simultaneous formation of two hexagonal hydrates CaOAl2O310H2O and 2CaOAl2038H20 which differ greatly in their kinetics of formation.

National audience; The comminution of monocalcium aluminate depends both on the grinding process and the composition of the solid : an "Aurec" vibrating crushing mill is more acting than a planetary ball mill. The subsequent reactivity of the solid versus water is more enhanced for "super-stoichiometric" aluminate (C/A=1.04) than for "sub-stoichiometric" one. Moreover, a connection between both the "balling fitness" of the solid and its activation during grinding was pointed out, what let suppose that entities responsible of the balling phenomenon take a prominent part in the hydration kinetics and can be considered as aluminate vacancies precedently identified.