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International audience; Two organosolv lignins from different origins, namely, almond shells and maritime pine, were modified by using a nanoclay and nanosilicate. Prior to modification, they were activated via glyoxalation to enhance the reactivity of the lignins and thus ease the introduction of the nanoparticles into their structure. The lignins were characterized by several techniques (Fourier transformed infrared, high-performance size exclusion chromatography, 1H NMR, X-ray diffraction, and thermogravimetric analysis) before and after modification to elucidate the main chemical and structural changes. The reaction with glyoxal proved to increase the amount of hydroxyl groups and methylene bridges. This tendency was more pronounced, as the percentage of glyoxal was incremented. On the other side, the addition of the nanoclay and nanosilicate particles improved the thermal stability of the lignins compared to that of the original unmodified ones. This trend was more evident for the lignin derived from maritime pine, which displayed better results regarding the thermal stability, indicating a more effective combination of the nanoparticles in the lignin structure during the modification process.

International audience; This article reports the ability of oligo(ethylene glycol)-based stimuli-responsive microgels to spontaneously form self-assembled microgel films under different conditions such as the presence or absence of water soluble polymers (WSP, formed during the microgel synthesis) and the type and/or amount of salt in the microgel dispersion. The unusually high encapsulation of four different cosmetically active molecules has been achieved via hydrophobic interactions and hydrogen-bonding interactions between the -OH groups of active molecules and ether functions of self-assembled microgel films. The loaded-films present absorption higher than 50% of the UVA-UVB wavelengths and can be used for skin protection against sun. The nature of the interactions was determined by NOESY-NMR spectroscopy in the gel state. Moreover, confocal microscopy was used to show that the water solubility of the active molecule plays a crucial role in obtaining a more homogeneous distribution in films after loading.

cited By 0; International audience; Hydroquinone (HQ) is known to form organic clathrates with some gaseous species such as CO2 and CH4. This work presents spectroscopic data, surface and internal morphologies, gas storage capacities, guest release temperatures, and structural transition temperatures for HQ clathrates obtained from pure CO2, pure CH4, and an equimolar CO2/CH4 mixture. All analyses are performed on clathrates formed by direct gas–solid reaction after 1 month’s reaction at ambient temperature conditions and under a pressure of 3.0 MPa. A collection of spectroscopic data (Raman, FT-IR, and 13C NMR) is presented, and the results confirm total conversion of the native HQ (α-HQ) into HQ clathrates (β-HQ) at the end of the reaction. Optical microscopy and SEM analyses reveal morphology changes after the enclathration reaction, such as the presence of surface asperities. Gas porosimetry measurements show that HQ clathrates and native HQ are neither micro- nor mesoporous materials. However, as highlighted by TEM analyses and X-ray tomography, α- and β-HQ contain unsuspected macroscopic voids and channels, which create a macroporosity inside the crystals that decreases due to the enclathration reaction. TGA and in situ Raman spectroscopy give the guest release temperatures as well as the structural transition temperatures from β-HQ to α-HQ. The gas storage capacity of the clathrates is also quantified by means of different types of gravimetric analyses (mass balance and TGA). After having been formed under pressure, the characterized clathrates exhibit exceptional metastability: the gases remain in the clathrate structure at ambient conditions over time scales of more than 1 month. Consequently, HQ gas clathrates display very interesting properties for gas storage and sequestration applications.

International audience; In this work, we report the use of the diffusion-ordered spectroscopy (NMR DOSY) nuclear magnetic resonance (NMR) technique to follow the nitroxide-mediated polymerization (NMP) of methyl methacrylate (MMA), well known as a difficult monomer to polymerize by NMP. Two syntheses were carried out either in the presence or absence of a small amount of styrene at 80 °C, using N-tert-butyl-N-(1-diethylphosphono-2,2-dimethylpropyl)nitroxide (SG1) as a control agent and 2-methylaminoxypropionic-SG1 alkoxyamine (BlocBuilder) as the initiator. Diffusion coefficients determined from NMR DOSY experiments could be accurately correlated to the weight average molar masses Mw of PMMA, and could thereby be used to confirm that the polymerization of pure MMA by NMP is uncontrolled due to disproportionation side reactions leading to non-reversible termination (i.e. dead chains). In a similar manner, the livingness of the PMMA chains grown in the presence of a small amount of styrene was confirmed by the linear evolution of the diffusion coefficient versus time (conversion) and the retention of the alkoxyamine chain end. Livingness was further assessed by NMR DOSY analysis of chain extensions with n-butyl acrylate. This all-in-one technique permits disproportionation side reactions, livingness, and evolution of the molar masses with time to be simultaneously followed.

International audience; Organic clathrate compounds, particularly those formed between hydroquinone (HQ) and gases, are supramolecular entities recently highlighted as promising alternatives for applications such as gas storage and separation processes. This study provides new insights into CO2–HQ clathrate, which is a key structure in some of the proposed future applications of these compounds. We present a novel synthesis and purification of CO2–HQ clathrate monocrystals. Clathrate crystals obtained from a single synthesis and native HQ are characterized and compared using Raman/Fourier transform infrared/NMR spectroscopies, optical microscopy, and thermogravimetric analysis coupled to mass spectrometry. The molecular structure of the clathrate has been resolved by X-ray diffraction analysis, and detailed crystallographic information is presented for the first time.

International audience; Fullerene is used as a monomer in this simple method to prepare soluble, well-defined polymers. The sterically controlled azomethine ylide cycloaddition polymerization of fullerene (SACAP) yields macromolecules with molecular weights of around 25 000 g mol-1. Importantly, cumbersome comonomers are employed to restrict cross-linking. Extensive characterizations, with the help of modeling studies, indicate that the polymers are regio-irregular with a majority of trans-3 isomers. Of particular interest is the exceptional ease of preparing polymers with zero metal content. © 2016 American Chemical Society.

International audience; Among the numerous reduced bandgap polymers currently being developed, poly[3-(4-octylphenyl)thiophene)]s (POPT) may present attractive properties for organic solar cells due to its facile preparation and improved absorption with respect to poly(3-hexylthiophene). This article appraises methods of preparation, including the use of diphenyl ether as a reaction medium, and discusses the effects of variations in molar masses, from about 3200 to 65,000 g mol -1 and regioregularity on its optoelectronic properties. The photovoltaic properties of POPT with [6,6]-phenyl C 61 butyric acid methyl ester (PCBM) in bulk heterojunction devices are also discussed in the light of morphological variations, as indicated by atomic force microscopy characterizations. With an initial screening of conditions, namely POPT:PCBM ratios and deposition solvent, a power conversion efficiency of 1.58% was obtained using a relatively high molar mass POPT sample.

cited By 20; International audience; In this work, we report the synthesis of poly(n-butyl acrylate-co-methyl methacrylate) copolymers by the nitroxide mediated polymerization (NMP) technique, using N-tert-butyl-N-(1-diethylphosphono-2,2-dimethylpropyl)nitroxide (SG1) as a control agent and 2-methylaminoxypropionic-SG1 alkoxyamine (BlocBuilder®) as the initiator. The copolymers are synthesized either by batch or semi-batch processes and the gradient profile is examined via the determination of the instantaneous fraction of monomer incorporated in the copolymer. A control of the molar mass together with low molar mass distribution (Mw/Mn < 1.4) is observed. The dependence of the copolymer glass transition temperature with conversion was followed by differential scanning calorimetry. The copolymers are investigated by carbon nuclear magnetic resonance and heteronuclear multiple bond correlation (HMBC) NMR sequences to study the effect of the monomer addition mode on the microstructure of copolymers. The thermomechanical properties of gradient copolymers are finally reported to establish the effect of the composition on the mechanical behaviour of the copolymers. © 2011 The Royal Society of Chemistry.

International audience; Intrinsically conducting polymers are of great interest for a large number of applications. But among the major drawbacks are their low solubility in common solvents and their poor mechanical properties. Elaboration of composites associating a matrix, bringing its mechanical properties, and polyaniline, as the conducting polymer, is a way of overcoming these disadvantages. Chitosan-graft-polyaniline copolymers were synthesized by simple oxidative method. The grafting reaction was quite complete, and it was found that the copolymers cross-linked to yield a composite hydrogel in which the polyaniline was homogeneously embedded. The conductivity of precursor (block copolymer) and gels was found to be larger than 10-2 S •cm-1. The composite gels were characterized in terms of swelling and rheological properties. They can be classified as "superabsorbent" hydrogels, and the swelling is reversible. The composite gels were then successfully used as actuators.

cited By 6; International audience; The rheological behavior in 1 M NaCl obtained from the modification of sodium poly(acrylate), PAANa, with n-dodecyl (C12) and n-butyl (C4) side chains was studied. A series of mono- and bigrafted hydrophobically modified PAANa polymers with high weight-average molar masses were prepared through one-pot polymer postmodification, monografting with 2 mol % of long C12 alkyl groups and 2 and 10 mol % of short C4 alkyl groups and bigrafting with 2 mol % of C12 and 2 or 10 mol % of C4. Molar mass measurements show that no degradation of chain occurred during these reactions. H NMR was carried out at 85°C on the acidic form of the polymers, wherein the polymer microstructures were observed to agree well with the feed ratio. It was observed that for bigrafted copolymers, the C4-C12 modified polymers exhibit a similar trend as the C12 modified polymer, with an unexpected synergistic improvement of the viscosifying effect at low polymer concentrations and a strong decrease in intrinsic viscosity.

cited By 38; International audience; This study shows that reasonably controlled nitroxide-mediated polymerization of acrylamide is achieved in pure water solution at 120 °C and high concentration (40 wt%), using a combination of a conventional hydrosoluble radical initiator (Vazo56) and a β-phosphonylated nitroxide, SG1. Moreover, some chain extensions can be performed from a polyacrylamide macroinitiator. Under these experimental conditions, we have demonstrated the conservation of the acrylamide structure without hydrolysis side reactions. The physico-chemical characterizations of polymers obtained from this method demonstrates that the controlled growing chain arises as a star-like shape from the hydrophobic core composed of SG1-functionalized polyacrylamide in the presence of a slight excess of SG1. © 2007 Elsevier Ltd. All rights reserved.

cited By 35; International audience; Two hydrophobically modified polyacrylamides (HMPAMs) with different molar contents of t-octylacrylamide as hydrophobic comonomer (1 and 1.5%molar) were synthesized by aqueous micellar copolymerization in water. The molecular structure was characterized in detail by light scattering and viscometric measurements using automatic continuous mixing (ACM) techniques in dilute solution. There was no significant difference between the weight average molecular weight (Mw) of homopolyacrylamide and the copolymers. The elucidation of polymer microstructure by 1H NMR showed that the hydrophobe content in the polymer backbone is almost the same as the hydrophobe content in the feed. This study reveals that branched t-octyl alkyl chains are not hydrophobic enough to induce significant associating properties, but can exhibit strongly magnified thickening properties in the presence of surfactant. The effect of NaCl addition to the solutions of the prepared HMPAMs was also explored as well as their interactions with sodium dodecyl sulfate (SDS) or cetyltrimethylammonium p-toluenesulfonate (CTAT). A direct comparison of the influence of spherical surfactant micelles and worm-like micelles on the rheological properties of the same polymer samples was made. For a given HMPAM copolymer at a fixed concentration in deionized water, the solutions zero-shear viscosities tend to increase upon adding surfactant, then they go through a maximum and then decrease (in the case of CTAT the viscosity after the maximum tends to slowly increase with CTAT concentration). These well known effects are due to the hydrophobic interactions between HMPAM and SDS or CTAT. The maximum viscosity occurs in HMPAM/SDS deionized water solutions. However, we demonstrate that by the addition of salt, the HMPAM/CTAT solutions can exhibit much higher viscosities (two orders of magnitude) than HMPAM/SDS solutions at low CTAT concentrations and high ionic strengths (larger than 1.5 M NaCl). This pronounced increased in viscosity is attributed to the growth of the CTAT worm-like micelles as the ionic strength increases, which can interact with the hydrophobic groups present in the HMPAMs and can form an entangled interacting network in solution.

International audience; Poly[3-(4-octylphenyl) thiophene] (PORT) and poly[3-(4-octylphenoxy) thiophene] (POPOT) with high head-to-tall regioregularitlis have been synthesised and photovoltaic properties have been investigated. POPT-blend-PCBM exhibits an interesting behaviour in bulk heterojunction whereas POPOT presents poor photovoltaic performances. UV-visible absorption and AFM images of the blends are presented to explain these results. Copyright © 2008 WILEY-VCH Verlag GmbH & Co. KGaA.

cited By 9; International audience; Several oligomers analogous to poly(p-phenylene vinylene) (PPV) were synthesised by the Wittig reaction, to be used as model compounds for the study of structure/properties relationship. They are based on benzene-1,4-bis(phenylene vinylene) (OPPV) substituted by electron-withdrawing (nitro) or electron-donating (methyl and dimethylamino) groups on the terminal rings of the molecule. Moreover, two other oligomers 2-hexadecyloxy-5-methoxybenzene-1,4-bis(phenylene vinylene) (1-16-OPPV) and 2-hexadecyloxy-5-methoxybenzene-1,4-bis(4-dimethylaminophenylene vinylene) (1-16-NC-OPPV) were prepared with alkoxy groups on the central ring of the molecule. After a complete structural characterization by FTIR, 1H and 13C NMR, particular emphasis was placed upon the investigation of their thermal stability by TGA and their optical properties in tetrahydrofuran (THF) solutions. Depending on the substituent and on its position in the molecule a different thermal behaviour was observed. Moreover, a red-shift from 10 to 50 nm was observed for the emission wavelength, with respect to unsubstituted OPPV. Several model compounds (with donating groups) exhibited high fluorescence quantum yields, from 51% to 68%. On the other hand, a very low yield was obtained for the oligomer with nitro groups, that was explained from semi-empirical calculations. These results showed promising properties for the incorporation of these oligomers in electroluminescent diodes.

International audience; Various poly[3-(4-octylphenyl)thiophene]s (POPTs) were prepared either by oxidative polymerisation or by chain-growth Grignard metathesis (GRIM). In accordance with previous results, the former polymerisation yielded polydisperse POPT. The method based on the GRIM reaction made possible the preparation of medium and higher molecular weight polymers with lower polydispersities. The POPTs were found to have band-gaps of ca. 1.7 eV. The photovoltaic characteristics of POPTs-blend-[6,6]-phenyl C61 butyric acid methyl ester (PCBM) composites under AM 1.5 conditions in standard ITO/PEDOT-blend-PSS/ POPT-blend-PCBM/LiF/Al solar cells were studied. It was found that POPT prepared via GRIM could deliver greater efficiencies than its equivalent prepared by oxidative polymerisation. It is expected that access to even higher molecular weight POPTs may improve the efficiencies of such devices.

cited By 47; International audience; Unsaturated Xanthan derivatives, which can be used for the development of biodegradable three-dimensional networks having hydrogel properties, were prepared by esterification under various conditions. Xanthan gum derivatives with different degrees of substitution were obtained by reaction with an unsaturated organic acid (acrylic acid) or with acid reactive derivatives (acryloyl chloride, maleic anhydride). The presence of acrylate and maleate groups in the modified structure of Xanthan gum was detected by ATR-FTIR, 1H liquid NMR and 1H HRMAS NMR spectroscopies. The degree of substitution as determined by 1H NMR could be controlled by varying the chemical nature of functionalisation agent, reaction time and temperature. The results proved that this polysaccharide can be modified by esterification with acids or unsaturated acid derivatives for further synthesis of hydrogels. Maleic anhydride presents a higher reactivity as compared to acrylic acid and acryloyl chloride. © 2007 Elsevier Ltd. All rights reserved.

International audience; Snake-cage gels were prepared using monodisperse polystyrene (PS) nano-size particles (R = 200 nm) in place of the more usually used linear polymer. The kinetics of the formation of the complementary polyacrylamide (PAM) hydrogel was studied alone or in the presence of the PS nanoparticles by 1H-NMR. Without PS, the reactivity ratios of the acrylamide (Am) and the crosslinking agent N,N'-methylene-bisacrylamide (BisAm) were computed using the initial kinetics of PAM gel at high crosslinker concentration (rA= 0.52, rB = 5.2, for Am and BisAm respectively). In the presence of PS, during the formation of nanoparticles composite gels (NPC gels), there was a decrease of the conversion rate with an increasing fraction of PS nanoparticles. This could be explained by steric effects which induce an increase of the elastic modulus of the matrix with the increasing fraction of PS nanoparticles. There was a considerable increase of the rheological properties of the NPC gels (i.e. tensile modulus) which was more pronounced at higher fractions of nanoparticles. We used the particular mechanical properties to develop a stimulus responsive (“smart”) material, i.e. a mechanoelectrical effect which may be used in the development of soft and wet tactile sensing devices

Monomer reactivity ratios in controlled radical copolymerization of styrene (S) and methyl acrylate (MA) monomers at 120 °C were determined. The Fineman–Ross method was used to calculate rs and rMA. Using this method, monomer reactivity ratio values of 0.89 and 0.22 were calculated for styrene and methyl acrylate, respectively. Because of the different reactivity ratios between the two monomers, and according to the molar fractions of two monomers, S/MA statistical or gradient copolymers were synthesized by nitroxide-mediated polymerization. Indeed, for different monomer ratios, the same statistical or gradient copolymers can be obtained by batch nitroxide mediated polymerization. These copolymers have been characterized by 1H nuclear magnetic resonance and size exclusion chromatography, and evolution of the composition has been correlated with the glass transition temperature measured by differential scanning calorimetry. Integrated intensities of the three observed peaks of (–OCH3) group in the 1H NMR spectra were used to determine the MA/MA/MA, MA/MA/S and S/MA/S triad sequences in the copolymers. Specific organization at the air/polymer interface of such copolymers has also been demonstrated by comparison between classical and attenuated total reflection (ATR) Fourier transform infra-red spectra.

A simplified route to regio-regular poly(3-alkylthiophene)s (P3AT) with predetermined molecular weights and low molecular weight distributions based on the chain-growth GRIM polymerisation of 2,5-dibromo-3-alkylthiophenes is detailed. It is proposed by way of in-depth 13 C-, 1 H- and two-dimensional NMR characterisations that the resulting P3ATs are quasi-100% regio-regular except for one regio-irregular pair at one chain-end. It is probable that chain-end groups exhibit reduced conjugation with the rest of the polymer. A comparison of the preparation of poly(3-hexylthiophene) and poly(3-butylthiophene) (P3BT) is presented. New methods required for the hydrogenation, formylation and bromomethylation of the chain-ends of P3BT, necessary to overcome its poor solubility and low reactivity, are described.

International audience; We report in this paper an original method for the synthesis of polybutylacrylate grafted on silica particles. First, we use the Stoeber method to synthesize silica particles with a narrow size distribution. An initiator for radical-chain controlled polymerization is then grafted on the silica surface in two steps. Trimethoxysilylpropyl methacrylate (TPM) is first grafted on silica by simple condensation. Then, a alkoxyamine initiator N-tert-butyl-N-1-diethylphosphono2,2-dimethylpropyl-0,1-methoxycarbonyl ethylhydroxylamine (MONAMS) reacts with the CC double bond of the TPM to form the grafted initiator of radical polymerization. The last step is the grafting of butylacrylate. For this, we use living free radical polymerization that allows to control the molecular weight and the polydispersity of the polybutylacrylate chains. We show that this synthesis method makes it possible to obtain a colloidal suspension of silica particles having a mean size of about 88 nm, a weak polydispersity and an important grafting density of polybutylacrylate (PBA).

cited By 40; International audience; Hybrid silica-particles comprising an inorganic core and an organic polymer shell have been synthesized by nitroxide mediated polymerization of butyl acrylate in the presence of a grafted alkoxyaroine. The layer of initiator molecules attached to the surface of silica is based on an acyclic β-phosphonylated nitroxide alsqreferred to SGL. The synthesis and the characterization by NMR of this aikoxyamine structure are briefly described. Moreover, the grafted initiator particles have been studied by XPS, NMR 29Si CP/ MAS, and TGA in order to determine the nature of the anchorage sites and the grafting density. With this stable radical as chain growth mctderator tethered to the inorganic core, it is demonstrated that the grafting from polymerization exhibits a control character with a: very low polydispersity index (I < 1.1). For the first time, a comparative study with a btmo-lecular System based on a grafted azoic initiator in presence of SG1 is also described, A different kinetic behavior has been demonstrated and interpreted in terms of variation of the initial [monamer]/[imtiator] ratio. © 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

cited By 106; International audience; Hydrophobically associating polyacrylamides (HAPAMs) or hydrophobically associating hydrolyzed polyacrylamides (HHAPAMs) are generally prepared by micellar copolymerization which leads to a blocky distribution of hydrophobes and drifted compositions. In the present study, a series of HAPAMs were prepared by direct N-alkylation of the amide groups of a parent polyacrylamide (PAM) in DMSO with alkyl bromide in the presence of potassium tert-butoxide. The derivatives HHAPAMs with various charge densities were obtained by partial hydrolysis of HAPAM precursors with 0.25 M NaOH in a 0.1 M NaCl aqueous solution at 50 °C. Molecular weight determination showed no degradation occurred in both processes. 1H and 13C solution NMR elucidations of hydrophobic group incorporation and degree of hydrolysis showed good agreements with feed ratio. Statistical hydrophobic group distribution along the polymer backbone was expected. For samples with high viscosity and poor solubility, gel HRMAS NMR was successfully employed. The results indicate that post-modification is a more effective way to control the composition of HAPAMs compared against micellar process. © 2002 Elsevier Science Ltd. All rights reserved.

cited By 11; International audience; Ziegler-Natta (TiCl4A1Et3) catalysts and ultrasound were used to prepare highly isotactic polystyrene (ca. 99%) with a molecular weight of 4.7 × 106 mol g-1 and low molecular weight distribution (Mw/Mn = 1.6) via a convenient method. Ultrasound was most effective if applied only during an initial stage in the polymerisation, most likely permitting dispersion of catalyst particles which were subsequently coated and separated by growing polymer chains. Yields could be improved by varying the amount of catalyst and reaction time © 2002 Published by Elsevier Science Ltd.