Search

In the present study, we investigated the effect of permodified 2,3,6-tri-O-trimethylsilyl β- and γ-cyclodextrin (TMS·β-CD, TMS·γ-CD) encapsulation on the optical, electrochemical, morphological, and supramolecular arrangements of a poly[2,7'-(9,9-dioctylfluorene-alt-2',7-fluorene)] PF copolymer. For this purpose, the photophysical properties and Langmuir monolayer formation of PF·TMS·β-CD and PF·TMS·γ-CD polyrotaxanes were investigated and compared with those of the reference PF. Surface pressure-area isotherms and Brewster angle microscopy studies indicated the capability of both polyrotaxanes to organize into larger and homogeneous 2D supramolecular assemblies at the air-water interface. The obtained results suggest that the presence of the surrounding TMS·β-CD and TMS·γ-CD macrocycles on the PF backbones leads to changes in the conformation and hydrophobicity of the film surfaces. Our investigation offers a method to assess the impact of TMS-CD encapsulation on the control of 2D monolayer formation, with particular attention on the generation of stable PF monolayers for organic electronic devices.

Electroactive polymers based on dielectric elastomers are stretchable and compressible capacitors that can act as transducers between electrical and mechanical energies. Depending on the targeted application, soft actuators, sensors or mechanical-energy harvesters can be developed. Compared with conventional technologies, they present a promising combination of properties such as being soft, silent, light and miniaturizable. Most of the research on dielectric elastomer actuators has focused on obtaining the highest strain, either from technological solutions using commercially available materials or through the development of new materials. It is commonly accepted that a high electrical breakdown field, a low Young's modulus and a high dielectric constant are targets. However, the interdependency of these properties makes the evaluation and comparison of these materials complex. In addition, dielectric elastomers can suffer from electromechanical instability, which amplifies their complexity. The scope of this review is to tackle these difficulties. Thus, first, two physical parameters are introduced, one related to the energy converted by the dielectric elastomer and another to its electromechanical stability. These numbers are then used to compare dielectric elastomers according to a general and rational methodology considering their physicochemical and electromechanical properties. Based on this methodology, different families of commercially available dielectric elastomers are first analyzed. Then, different polymer modification methods are presented, and the resulting modified elastomers are screened. Finally, we conclude on the trends enabling the choice of the most suitable modification procedure to obtain the desired elastomer. From this review work, we would like to contribute to affording a quick identification method, including a graphic representation, to evaluate and develop the dielectric materials that are suitable for a desired actuator.

The effects of LDPE and PET in contact with heritage object made in PVC were studied and compared with silk paper during an artificial aging consisting in a temperature cycle and under controlled relative humidity. Color changes, morphological changes of the surface, plasticizers loss and surfaces properties were assessed over aging time. More pronounced color changes than for the references (without contact material and with silk paper) are observed for both contact materials but are more significant for PET whose surface has brown spots from three months of aging. The plasticizers cross LDPE from the outset of the aging but zein (protein additive) is evidenced only on the side in contact with the PVC. The PVC sample in contact with PET shows phtalic acid from DOP degradation but it remains on the PVC surface.

International audience; The durability of paper documents treated with aminoalkylalkoxysilane copolymer (co-AAAS) flexible networks, as deacidifying and strengthenening agents, was studied. To this end, a 1922 lignocellulos ic newsprint paper was treated with co-AAASs and characterized. Physico-chemical properties such as pH, chromatism, opacity and mechanical strength were measured shortly upon treatment and several years after. In order to better understand the role of the initial degradation state of the paper and the impact of its constituents other than cellulose (lignin, alum-rosin sizing) on the treatment efficiency, several laboratory papers were added as models. It was shown that alum-rosin sizing contributed to a decrease in pH of the most degraded treated paper over the monitoring time, whereas the strengthening effect was mostly affected by the presence of lignin. In particular, for most papers, after several years, the gain in folding endurance was the lowest in the lignin-rich ones. The breaking length of all the papers increased post-treatment and over time, independently of the paper constituents. This was attributed to the slowly progressing aminoalkylalkoxysilanes polycondensation, on the scale of years, as evidenced by Cross Polarisation-Mass Angle Spinning 29 Si solid-state Nuclear Magnetic Resonance.

Context The FibriDerm project aims at the development and usage of fibrin-based biomaterials, with mechanical properties adapted to new applications. Methods These materials are elaborated from interpenetrating polymer networks in which a fibrin-based gel, obtained through enzymatic hydrolysis of fibrinogen, is associated with a synthetic polymeric network, synthesized by photochemistry. These materials are self-supported and not retractable, properties which open new fields of application for these biomaterials as mechanical support for cellular growth, and particularly relevant for tissue regeneration. Results The main goal of this project is to optimize already elaborated biomaterials to create Human Dermal Equivalents (HDE) solely made of cells and proteins from human origin. An intermediate material, capable of being colonized by surrounding cells and biodegradable in the long-term, will be first developed. Conclusion The FibriDerm project has the ambition to lead to the development of new materials for tissue regeneration, from the initial research developments and optimizations up to pre-clinical stages, via an interdisciplinary approach.

Polymethyl methacrylate (PMMA) is commonly used as organic glass for the protection of works in museums. However, their extreme sensitivity to scratching causes problems during maintenance procedures. In order to improve the resistance to abrasion, PMMA has been cross-linked with silica nanoparticles previously modified with 3-(methacryloxy)propyl-trimethoxysilane (MPTS). This functionalization allows both a homogeneous dispersion of the silica nanoparticles in MMA monomer and the PMMA crosslinking which has been confirmed by solid/liquid extraction and DMA analysis. The small nanoparticles (7–10 nm diameter) added in different amounts, are homogeneously dispersed in the transparent (T% > 80%) hybrid PMMAx-SiO2 networks as verified by TGA and TEM microscopy. These hybrid PMMAx-SiO2 networks have been then combined with a PCR39® polycarbonate network in an interpenetrating polymer network (IPN) architecture. The synthesis of a hybrid IPN in which one of the phases is cross-linked by the inorganic nanoparticles has been demonstrated for the first time. Finally, as expected, the incorporation of the silica nanoparticles improves the scratch resistance by a factor of 3 compared to all organic PMMA/PCR39® IPNs.

In this paper, the surface free-energy of 700 µm-diameter copper wires as well as its dispersive and polar components has been determined. For this, the measurement method developed for assessing advancing and receding contact angles of liquids on vertical wires has been validated with polytetrafluoroethylene (PTFE) as a well-known material. Thus, it has been checked that the dynamic contact angles of different model liquids, such as dimethylformamide, tri-cresyl phosphate or ethylene glycol, on a PTFE wire held vertically are similar to those obtained on a PTFE plane surface. Then, the Owens–Wendt approach was chosen to determine the polar and dispersive components of surface free-energy of the PTFE wire using a large range of model liquids. A surface free-energy γPTFE = 18.7 ± 1.6 mN m−1 was obtained with a high dispersive component, γd ≈ 17.3 ± 1.0 mN m−1, in comparison with the polar one, γp ≈ 1.4 ± 0.6 mN m−1. Using the same approach for the copper wire, a surface free-energy γCu = 25.7 ± 0.7 mN m−1 was determined including mainly dispersive forces (γd ≈ 25.1 ± 0.5 mN m−1).

International audience; Natural ageing of paper is responsible for its slow decay. Late 19th and early 20th century lignocellulosic paper collections of mediocre quality, especially newsprint papers, are often in poorer conservation state than medieval handmade rag papers. In order to find a conservation solution for Libraries and Archives collection keepers, CRC and LPPI have developed novel one-pot treatments based on the use of copolymerized aminoalkylalkoxysilanes (AAAS) that allow the simultaneous deacidification and strengthening of cellulosic objects of the cultural heritage [1]. Several paper constituents are thought to affect the efficiency of the copolymer treatment under study, including papermaking additives. In particular, alum-rosin sizing, and the presence of mechanical pulp [2,3], which contains copious amount of lignin, a biopolymer largely responsible for the acidity of early industrial paper, are thought to play an adverse role. Nuclear Magnetic Resonance (NMR) and Fourier-transform infrared (FTIR) spectroscopies were used to investigate the interactions and the reactions occurring between the AAAS and the paper at room temperature. Several model molecules that mimic the main organic functions on cellulose and lignin were brought into contact with AMDES (3-aminopropylmethyldiethoxysilane). The aim was to better understand the possible interactions between the biomacromolecules and the AAAS treatment by focusing on key characteristic functional groups. In parallel to the study with molecular models, copolymerized AAAS were sprayed on naturally aged newsprint papers from the early 20th century. The in situ copolymerization was studied using Solid-state 29 Si MAS NMR. The data was compared to data formerly obtained with a newsprint paper treated in 2015 with the same copolymers mixture. This allowed the long term monitoring of the polymerization in ambient conditions when the AAAS are in contact with lignocellulosic paper.

The mechanical properties and conductivity, as well as the water sorption and transport properties, of a new series of blends of perfluorosulfonated acid ionomer (PFSA, Aquivion ® ) and disulfonated poly(aryl ether ketone) (DS-PAEK) with compositions ranging between 10 and 90 wt% were studied. For 10–20 wt% sulfonated hydrocarbon polyelectrolyte blends, the main mechanical relaxation temperature of side chains of Aquivion ® increased 10–20 °C as compared to pure Aquivion ® . This shift demonstrates the presence of interactions between Aquivion ® and DS-PAEK while the ion exchange capacity, the capacity to absorb water, and the proton conductivity of blends remained very close to those of pure Aquivion ® . In addition, these new materials show improved robustness and better performance in fuel cell operation at 105 °C as compared to Aquivion ® . These results indicate that PFSA materials can be strengthened by adding a sulfonated hydrocarbon ionomer.

A new series of polyethylene glycol-albumin/Fibrin interpenetrating polymer networks (PEG-BSA/Fb IPNs) combining a fibrin gel with a co-network of polyethylene glycol and serum albumin has been developed in order to study the enzymatic degradation of such architectures combining protein and synthetic polymer partners. BSA provides biodegradability thank to its many segments cleavable by enzymes while PEG ensures material resistance (shape preservation, mechanical moduli, …). Previous the degradation study of these easily manipulable PEG-BSA/Fb IPNs, it was shown that each partner (fibrin, PEG and BSA) contributes to the elastic modulus value which is only possible in an IPN architecture where the different polymer partners form a continuous phase in the whole material. The homogeneous protein distribution in the materials was also confirmed by confocal microscopy. Then, their biodegradability was studied by combining three complementary characterizations: on the one hand, absorbance of the hydrolytic enzyme solution in which they were immersed to quantify the proportion of protein fragment extracted and, on the other hand, viscoelastic moduli of the hydrogels after immersion in the same enzyme to evaluate their mechanical resistance, and finally, MEB imaging to check the hydrolysis homogeneity. The proteolytic enzyme degrades quickly IPNs containing less than 3 wt% PEG while other IPNs remain resistant to proteolysis over long periods, although their viscoelastic properties are reduced by 70% and morphology at the microscopic level changed in a few hours. The degradation rate of these materials is thus easily tunable by composition adjustment.

International audience; Polyurethane (PUR) ester foams are found in 20th century museum collections in a variety of artworks and objects. Unfortunately PUR ester foams are prone to degradation, and present e among other plastic materials e important conservation issues. They are very sensitive to moisture, and their hy-drolysis leads to several degradation processes such as yellowing and embrittlement, drastically changing the artwork aspect and materiality. Few researches were conducted on the consolidation of PUR ester foams. In this paper, a curative treatment that should limit the hydrolysis of the degraded PUR foams, and that mechanically consolidate the foams' structure is presented. This work focuses on the innovative use of alkoxysilanes mixtures and on their application modes on foam samples. Different binary mixtures of OTMS (n-octyltriethoxysilane, hydrophobic and trifunctional) and AMDES (3-aminopropylmethyldiethoxysilane, hydrophilic and bifunctional) in various proportions were tested. The kinetic evolution of their polycondensation using spectral decomposition of FTIR spectra revealed that OTMS does not react with atmospheric water vapor and that the presence of an amine (AMDES) is required to initiate its polycondensation. This result justifies the use of a mixture of both siloxanes. The different treatments were then applied on artificially degraded PUR ester foams using concentration of 2.5% and 10% of alkoxysilanes in HMDS (hexamethyldisiloxane, solvent). The treatment was applied by pouring the solution over the samples and resulted in a homogeneous impreg-nation of the foams, whereas vaporization modes were unsuccessful regarding the penetration of the treatment in the foam cells. The hydrophilicity of the treatments was characterized using water contact angle measurements and it appears that at least 25% of hydrophobic OTMS in the mixture is needed to decrease the wettability of the samples, in order to avoid further hydrolysis. The reinforcement properties were studied using mechanical tests, and resulted in a need of a solution of 10% (in HMDS) for an acceptable reinforcement. Finally, colorimetric measurements showed that the visual aspect of the degraded samples was improved with the treatment.

Various parameters that may affect the efficiency of tri- and di-functional aminoalkylalkoxysilanes (AAAS) copolymer treatments to deacidify and mechanically strengthen aged complex papers (lignocellulosic pulp, additives) were studied. Three model papers were first hydrothermally aged (90 °C—50% RH) in order to achieve physicochemical characteristics similar to those of a naturally aged newsprint, and were then treated with AAAS copolymers. The chemical composition of the treatments varied from 50 to 5 wt% of tri-functional monomer APTES, the latter acting as cross-linker in the copolymer network. The respective ratio of tri- and di-functional monomers in the mixture was shown to greatly influence the mechanical properties of the treated papers in the case of APTES/DIAMINO but less so in the case of APTES/AMDES. If APTES/DIAMINO (50/50 wt%) did not strengthen the degraded papers, a higher proportion of DIAMINO (95 wt%) and lower proportion of APTES (5 wt%) led to improving the tensile strength and, more importantly for the function properties of paper, significantly enhancing the folding endurance. The treatment efficiency decreased at higher state of deterioration of the papers and in the presence of alum–rosin sizing. Lastly, the treatments developed for the artificially aged model papers were applied to the degraded newsprint paper specimen and successfully enhanced its mechanical properties.

International audience; We developed original anion exchange membranes to protect air electrodes operating in aqueous lithium-air battery configuration, i.e. supplied with atmospheric air and in concentrated aqueous lithium hydroxide. These protective membranes have an interpenetrating polymer network (IPN) architecture combining a hydrogenated cationic polyelectrolyte network based on poly(epichlorohydrin) (PECH) and a fluorinated neutral network based on perfluoropolyether (Fluorolink ® MD700). Two phases, each one rich in one of the polymer, are co-continuous in the materials. This morphology allows combining their properties according to the weight proportions of each polymer. Thus, PECH/Fluorolink IPNs show ionic conductivity varying from 1 to 2 mS cm À1 , water uptake from 30 to 90 wt.% and anionic transport number from 0.65 to 0.80 when the PECH proportion varies from 40 to 90 wt.%. These membranes have been systematically assembled on air electrodes. Air electrode protected with PECH/Fluorolink 70/30 IPN shows outstanding stability higher than 1000 h, i.e. a 20-fold increase in the lifetime of the non-modified electrode. This efficient membrane/air electrode assembly is promising for development of alkaline electrolyte based storage or production energy systems, such as metal air batteries or alkaline fuel cells.

Interpenetrating polymer networks (IPNs) have gained great attention for a number of biomedical applications due to their improved properties compared to individual components alone. In this study, we investigated the capacity of newly-developed naturally-derived IPNs as potential biomaterials for tissue engineering. These IPNs combine the biologic properties of a fibrous fibrin network polymerized at the nanoscale and the mechanical stability of polyethylene oxide (PEO). First, we assessed their cytotoxicity in vitro on L929 fibroblasts. We further evaluated their biocompatibility ex vivo with a chick embryo organotypic culture model. Subcutaneous implantations of the matrices were subsequently conducted on nude mice to investigate their biocompatibility in vivo. Our preliminary data highlighted that our biomaterials were non-cytotoxic (viability above 90%). The organotypic culture showed that the IPN matrices induced higher cell adhesion (across all the explanted organ tissues) and migration (skin, intestine) than the control groups, suggesting the advantages of using a biomimetic, yet mechanically-reinforced IPN-based matrix. We observed no major inflammatory response up to 12 weeks post implantation. All together, these data suggest that these fibrin-based IPNs are promising biomaterials for tissue engineering.

International audience; The aim of the research was to evaluate the influence of certain components of paper such as lignin and papermaking additives (fillers and sizing) on the efficiency of a recently proposed treatment for simultaneous deacidification and mechanical strengthening with polyaminosiloxane copolymer networks. Mixed mechanical and chemical pulp papers containing various additives were treated with aminoalkylalkoxysilanes (AAAS) by immersion or by spray. Upon treatment, the deposited alkaline reserve varied from 0.34 to 1.14 mol kg −1 . For all the papers, copolymers formed from binary mixtures of a di- and a tri-functional AAAS provided the best improvement in the mechanical properties, i.e. in the tensile strength and the folding endurance, indicating an increase in the interfiber bonding energy and in the paper flexibility and plasticity, respectively. It was found that fillers had no influence while sizing hampered the efficiency of the treatment. The presence of mechanical pulp was shown to have a significant impact on the effect of the treatments as well by increasing the tensile resistance more than the folding endurance, indicating an increase in the paper rigidity. This observation was attributed to the response of lignin to the treatment.

New proton-conducting co-networks were synthesized, characterized and tested as Polymer Exchange Membranes for Fuel Cells application. The membranes were obtained from 2-acrylamido-2-methylpropane sulfonic acid (AMPS) copolymerized with a perfluoropolyether oligomer used as crosslinker (Fluorolink ® FMD700). The structure, the thermo-mechanical behavior, the transport properties and the stability were examined in function of the co-network composition, e.g. increasing amount of conductive AMPS. High proton conductivity (1.10 –3 –5.10 −3 S cm −1 ) was reached at a threshold composition of 10 wt% AMPS, which also corresponds to a significant increase in water sorption. The efficiency of proton transfer was shown to directly correlate to the phase-separated nanostructures. On increasing the AMPS content, hydrophilic clusters embedded in the mechanically-robust FMD700 percolate and a co-continuous 3D morphology is formed. Fuel cells tests performed using the high-AMPS content crosslinked membranes showed behaviors comparable to benchmark Nafion ® under similar conditions, with performances significantly improved when the temperature is increased.

Semi-Interpenetrating Polymer Networks (semi-IPNs) combining a fluorinated network with a linear sulfonated poly(etheretherketone)(S-PEEK) were synthesized in presence of DMAc as solvent. The effects of the evaporation conditions of solvent during fabrication process on water swelling, proton conductivity and thickness measurements suggest a morphology modification of the semi-IPN. SAXS and SANS measurements confirmed the structural modification of the S-PEEK and fluorinated phases leading to a decrease of the hydrophilic/hydrophobic domain nanoseparation when the drying time increases along with lower water swelling ability, proton conductivity, water self-diffusion coefficient. On the contrary, the immersion time of this semi-IPN into an acid solution to carry out the cation exchange does not affect its morphology.

Proton and water transport properties as well as water sorption, thermomechanical properties, and morphology of a new series of semi-Interpenetrating Polymer Network (semi-IPN) combining perfluorosulfonated ionomer (Aquivion®) with a neutral fluorinated network of composition ranging between 10 and 50 wt% have been studied. When less than 20 wt% of neutral fluorinated network are included, water and proton transport properties of semi-IPNs are enhanced compared to that of Aquivion®, despite of their decrease of ion exchange capacity and their capacity to absorb water. Thermal and chemical stabilities are maintained very close to those of Aquivion®. In addition, these new materials show similar performances in fuel cell operation at 105 °C compared to those of Aquivion®. That evidences that perfluorosulfonated ionomer can be strengthened by association with a neutral fluorinated network.

International audience; The nanostructure of a microemulsion can be strongly affected by the liquid-to-solid transition during polymerization. Here, we examined the evolution of nanostructures of different ternary mixtures, including two microemulsions and a single lamellar phase that upon polymerization are quantitatively studied by SAXS/WAXS and DSC experiments systematically performed before and after the polymerization of both aqueous and organic phases. Samples are mixtures of the poly(2-acrylamido-2-methylpropanesulfonic acid) network as the aqueous phase and poly(hexyl methacrylate) as the organic phase stabilized by Brij35 surfactant. Upon polymerization, the surfactant is excluded from the water/oil interface and crystallizes, strongly changing the nanostructure of samples where it is the main component. In samples where the aqueous phase is the main component, only a few changes in structure are observed upon polymerization. This study demonstrates quantitatively the possibility to preserve nanostructures during polymerization, thus inducing a templating effect.

PurposeThis paper aims to present a case study of some current disorders affecting the stone‐panels of façade claddings, i.e. cracking, spalling close to anchorage systems and staining. The purpose of this study is to identify the origin of the mechanical and chemical disorders of the carbonate rock thin panels of the “Les Chênes 1” building of the University of Cergy‐Pontoise (France).Design/methodology/approachMapping of the disorders, anchorage system investigation at spallings, chemical analyses of oil‐like stains were performed in order to characterize both disorders. Porosity and capillarity properties of the rock were measured and compared between samples collected outside and within a stain.FindingsMechanical disorders result from vandalism or poor implementation. Spallings are disorders very likely in evolution. Their occurrence may increase through time. Stains are made of silicone destabilization products.Originality/valueA model is proposed for the formation of oil‐like stains. Water is required to destabilize silicone sealant and to drive the migration of the degradation products through the porous media and towards the surface of the plate exposed to rainfall.

Monolayers of a cellulosic polymer bearing cinnamate groups were characterized at the air-water interface by combining isotherm measurements, Brewster angle microscopy, and infrared-visible sum-frequency generation (SFG) spectroscopy. This spectroscopic technique was used to detect the photochemical behavior of the cinnamate groups upon UV photoirradiation of the monolayers. From the disappearance of the C═C mode and the absence of a change in the C═O mode, it could be concluded that isomerization is the dominant photoreaction for a monolayer of this polymer. This conclusion was corroborated by a comparison of the spectra of the monolayer after irradiation with spectra measured for monolayers spread from preirradiated solutions, for which it is known that isomerization is the main process.

Solid anion-exchange membranes that display interpenetrating polymer network (IPN) architecture were developed to be assembled on air electrode surface to improve its electrochemical stability in alkaline environment. The IPN membranes associate an anionic conducting polyepichlorohydrin network entangled within a cross-linked poly(2-hydroxyethyl methacrylate) in different mass proportions. The membranes possess suitable mechanical and thermal properties, an ionic conductivity of about 1 × 10 −3 S cm −1 and suitable cation selectivity. The electrochemical behaviour of the air electrode/IPN membrane assemblies (AEMA) were then evaluated in LiOH 5 M. The polarization curves indicate that a good electrochemical interface was established between the electrode and the IPN membranes. Moreover, the AEMA exhibits a discharge stability in LiOH 5 M ten times higher compared to a bare electrode under the same conditions.

The photochemical behavior of photosensitive materials obtained by spin-coating or network synthesis of a cellulosic polymer bearing photo-cross-linkable cinnamate groups was investigated. First, cinnamate groups were grafted on a cellulose acetate butyrate polymer, with different grafting densities. The photochemical properties of the polymers were studied in solution by UV–visible and 1H NMR spectroscopy. Then spin-coated films and networks were prepared and characterized as a function of the number of cinnamate groups per cellulosic unit. The water-wetting properties of both surfaces were studied by dynamic contact angle measurements, before and after photoirradiation, and subsequent heating. The surfaces obtained by the two methods have significantly different behaviors that can be assigned to the distinct photochemical pathways of the cinnamate groups upon irradiation depending on the sample preparation. Indeed, dimerization reaction is evidenced as the main process in the spin-coated films while the expected isomerization is predominant at the surface of the polymer networks.

The aim of this paper is to summarize recent progress on full interpenetrating polymer networks (IPNs) and semi-interpenetrating polymer networks (semi-IPNs) as proton-conducting membranes for use in fuel cells. IPN materials possess a series of unique properties, by virtue of which they represent particularly suitable candidates for this application. Although IPNs have been thoroughly studied for 50 years, fundamental research and/or applications of IPNs in the field of fuel cells remain little explored. A short review summarizing investigations carried out on these particular materials as protonic membranes could prompt the development of these highly promising architectures in this field, the environmental importance of which is growing exponentially.

Rechargeable aqueous lithium-air cells have been developed and manufactured with the objective of analysing the limitations of the technology. The barriers to the technology have been identified and solutions to some of them have been successfully demonstrated in this study.

New amphiphilic cyclodextrins are synthesized by selective modification. Two synthetic strategies are investigated. Per-(6-thio-2,3-trimethylsilyl)cyclodextrins can only be obtain by synthesizing first the per-6-thio-cyclodextrin and then silylating the remaining hydroxy functions. Characterizations of the products were achieved by ESI-MS and intramolecular coupling between thiol functions was evidenced. These new compounds are shown to be amphiphilic, and form stable Langmuir–Blodgett films that can be transferred on the upstroke and the downstroke of a substrate with a transfer ratio close to unity.

The behavior at the air–water interface of amphiphilic α, β and γ trimethylsilyl per-modified cyclodextrin ( p TMS-CD) monolayers is reported, as a first step towards the building up of a Langmuir–Blodgett assembly with potential gas sensor properties. The p TMS-CDs form stable monolayers with unusually high collapse pressure. It is shown that this peculiar behavior arises from a partial hydrolysis of TMS groups at the air–water interface. This hydrolysis reaction was confirmed by infrared spectroscopy and the departure of TMS groups was evidenced by weight loss measurements through quartz crystal microbalance carried out on the p TMS-CD monolayers deposited through the Langmuir–Blodgett technique.

Combinations of fluorinated and silicone based elastomers were elaborated through the in situ synthesis of interpenetrating polymer networks (IPNs). The PDMS network was formed by dibutyltindilaurate catalyzed addition between the hydroxy end groups of α,ω-(3-hydroxypropyl)polydimethylsiloxane (PDMS) and a pluriisocyanate cross-linker. The poly(fluorinated acrylate) (polyAcRf6) network was obtained from free-radical copolymerization of a fluorinated acrylate with ethylene glycol dimethacrylate in the presence of dicyclohexyl peroxydicarbonate as the initiator. IPNs with different relative weight proportions of the fluorinated vs silicone partners were characterized by DMTA and DSC. Density refractive index and contact angle measurements reveal a satisfactory interpenetration degree of PDMS and polyAcRf6 networks. In addition, these materials present an unusual variation of density values and of the surface properties as a function of the relative weight composition.

Acrylate polymers are one of common organic glass family. However their sensitivity to abrasion is an important drawback. Various alternatives were considered but they are often expensive. In this work, we show that the polymethylmethacrylate (PMMA) glass resistance can be improved by performing materials based on Interpenetrating Polymer Network (IPN) at low cost. A series of transparent IPNs based on an aliphatic polycarbonate and PMMA was synthesized through in situ polymerization process. The formation of two networks in the IPNs was studied by FTIR spectroscopy. Effects of PMMA cross-linking and partner proportions in the IPNs were investigated by dynamic mechanical thermal analysis. Optical properties, solvent and scratch resistances have been also studied.

International audience; The design of interpenetrated networks (IPN) membranes for fuel cell applications requires both an electrolyte and a neutral network. The composition and architecture of the latter are of major importance for the final IPN membrane properties. In this work, networks based on a fluorinated diepoxy oligomer (DFODDE) and a non-fluorinated triepoxy monomer (TMPTGE) were synthesized. The network composition was varied from 100% DFODDE to 100% TMPTGE, resulting in an increase of the crosslinking density and concomitantly a decrease of the fluorine content. The curing process was optimized to achieve a total epoxy conversion and the chemical structure of the networks was characterized by Raman and Infrared spectroscopies. The physical, thermal and chemical membrane properties were studied and discussed as a function of the crosslinking density and of the fluorine content. Increasing the crosslinking density led to a decrease of the membrane permeability to oxygen. Water sorption properties depended on both parameters, with a prevailing role of the fluorine content on the water uptake and a major influence of the crosslinking density on the diffusion parameter. The thermal stability increased also with the fluorine content. All materials exhibited a good stability in water at 80 degrees C but a significant weight loss after immersion in a concentrated H2O2 solution. Altogether, these results indicate that networks containing 20% of TMPTGE exhibit an interesting set of properties (low oxygen permeability, high T-g, good chemical and thermal stability) to behave as a neutral partner in an IPN membrane. Moreover, the low water uptake and diffusion rate measured in these networks make them attractive for water barrier membranes.

International audience; Aqueous alkaline metal-air batteries represent promising energy storage devices when supplied with atmospheric air. However, under this condition, the air electrode shows a very short life time (i.e. 50 h of operation in 5 M LiOH at À10 mA cm À2), mainly due to the precipitation of carbonates inside the electrode porosity. The air electrode can then be protected by an anion exchange membrane on the electrolyte side. In this paper, we demonstrate that the efficiency of this protective membrane depends on the assembly method on the electrode. When a modified poly(epichlorohydrin) (PECH) network is synthesized directly on the electrode, the polymer seeps inside the electrode porosity, and a suitable interface inducing negligible additional polarization in comparison with classical pressure-assembled membranes is obtained. This protected electrode shows improved stability of up to 160 h of operation in 5 M LiOH. This performance is improved to 350 h by adjusting the conductivity and the ionic exchange capacity. Finally, the interest of interpenetrating polymer network (IPN) architecture compared to a single network is confirmed. Indeed, an electrode protected with a PECH/poly(2-hydroxyethyl methacrylate) (PHEMA) IPN is stable for 650 h in 5 M LiOH. In addition, degradation process becomes reversible since the assembly can be regenerated, which is not possible for the bare electrode.

Interpenetrating polymer networks combining cellulose acetate butyrate (CAB) and α,ω-divinyl-polydimethylsiloxane (PDMS) in different weight proportions have been synthesized. The synthesis involves a one pot–one shot process in which all components are first mixed together. For each composition, the relative CAB and PDMS network formation rates are adjusted through the concentration of DBTDL used as CAB network formation catalyst. Thus, the chemically independent networks are formed quasi-simultaneously in order to avoid phase separation. The CAB cross-linking density effect on the PDMS/CAB IPN mechanical properties has also been particularly studied. All synthesized IPNs are transparent and only one mechanical relaxation temperature lying between those of the single CAB and PDMS networks is observed by DMTA analysis. These results show that the networks are correctly interpenetrated and no phase separation is observed at the DMTA level. Some mechanical properties of the PDMS network are significantly improved in this IPN combination and their stress–strain behavior has highlighted a synergistic effect arising from the IPN architecture. Thus, these IPNs exhibit many characteristics, which would allow defining them as close to ‘true’ IPNs.

In order to improve polyisobutene (PIB) mechanical properties, a PIB network is combined with a polystyrene (PS) one into an interpenetrating polymer network (IPN) architecture. PIB network is formed by alcohol addition between the hydroxyl end groups of a telechelic dihydroxy-polyisobutene and a pluri-isocyanate. PS network is synthesized by free-radical copolymerization of styrene with divinylbenzene. Thus, the optimal synthesis conditions are determined by FTIR spectroscopy and the kinetics of the alcohol–isocyanate addition is studied in detail. A short kinetic study of the PS network formation inside the PIB network is also carried out. The highest degree of interpenetration is obtained by forming the PIB network first. The corresponding transparent IPNs exhibit two mechanical relaxations corresponding to those of PS and PIB enriched phases. However, mechanical properties of PIB networks are tremendously improved by the presence of a PS network in such IPN architectures.

The synthesis of an interpenetrating polymer network (IPN) combining a polydimethylsiloxane (PDMS) network and a cellulose acetate butyrate (CAB) network is reported. The silicone network is formed through a thiol-ene addition between α,ω-divinyl-poly(dimethylsiloxane) and trimethylolpropane tris(3-mercaptopropionate) as a cross-linking agent. The CAB network is synthesized by pluri-isocyanate cross-linking through dibutyltindilaurate (DBTDL) catalysis. The IPN is prepared through a one pot-one shot process. Kinetic studies of the IPN synthesis showed that some thiol cross-linking functions react with DBTDL which slows down the CAB network formation by decreasing the available quantity of DBTDL catalyst. Thus, in order to obtain a transparent material withstanding the presence of thiol groups, the DBTDL content must be increased and the resulting IPN exhibits then only one transition temperature as measured by dynamic thermomechanical analysis witnessing a high level of interpenetration.

Polycarbonates (PC) are currently used for organic optical glass; nevertheless they show a poor impact resistance which may be increased by combination with cellulose acetate butyrate (CAB) into a PC/CAB interpenetrating polymer network (IPN), without altering the material transparency as we show here. A series of rigid IPNs based on an aliphatic polycarbonate and CAB was prepared through in situ polymerization techniques. The kinetics of the formation of two networks in the IPNs were studied by FTIR spectroscopy. Effects of the CAB cross-linking and weight proportions of the two components in the IPNs were investigated by dynamic mechanical thermal analysis.

In this study, we have used an EDT derivative with a tetradecyloxy chain (EDTMC14) that renders the monomer soluble in organic solvents as well as suitable for Langmuir–Blodgett (LB) experiments. EDTMC14 monomer was investigated regarding its spreading and polymerization behavior at the air–water interface. The polymerization at the interface depends on the CAN concentration and pH in the subphase. For comparison, we have studied the behavior of the corresponding polymer (PEDTMC14) obtained by chemical polymerization. The different LB films showed the same characteristics in FTIR spectroscopy and electrochemistry and conductivity measurements. These results may indicate that both polymers have essentially the same molecular structure in the p-doped state, and that the pre-organization of the monomers in the Langmuir films seems to have no dramatic influence on the polymer properties.

International audience; Two di-alkoxysilanes, with (AMDES, ami-nopropylmethyldiethoxysilane) or without (DMDES, dimethyldiethoxysilane) an amine function, and a tri-alkoxy aminosilane (APTES, aminopropyltriethoxysi-lane) as well as their mixtures were introduced in paper as fiber strengthening agents. The polymerization and copolymerization of these polysiloxanes in the paper were investigated. In all the cases where APTES was present, the formation of networks was established by measuring the soluble fraction amount extracted from the treated papers. A slight decrease of the opacity of the paper sheets when AMDES was part of the treatment was noted. The presence of APTES reduced this opacity loss. The study of the physicochemical properties of the treated paper (mechanical strength and alkalinity) demonstrated that, besides the required deacidification feature, the different treatments allowed an efficient strengthening of the cellulose fibers to various extents. Contact angle measurements indicated a decrease of the hydrophilic character of papers treated with the mixture APTES/AMDES and the occurrence of a hydrophobic character of the papers treated with APTES alone. These results were consistently obtained for both spray and immersion treatment processes.

New interpenetrating polymer networks (IPNs), i.e., the combinations of two or more polymer networks synthesized in juxtaposition, have been synthesized with controlled structure using microemulsions as templates. Poly(2-acrylamido-2-methylpropanesulfonic acid) (PAMPS) was chosen as the hydrophilic network, and poly(hexyl methacrylate) (PHMA) as the hydrophobic network. Initially, a ternary phase diagram was constructed in order to determine the microemulsion structure versus its composition, with the phases containing corresponding monomers and polyoxyethylene lauryl ether (Brij35) as surfactant. Four different structures (reverse, lamellar, bicontinuous and direct) were characterized. Then, the free radical polymerization/cross-linking reaction was carried out for the different monomers in each phase of the microemulsions. Materials obtained after polymerization were analyzed to confirm the IPN architecture and the preservation of the original morphology of the microemulsions used as the template.

A fibrin hydrogel at physiological concentration (5 mg/mL) was associated with polyvinyl alcohol (PVA) inside an interpenetrating polymer networks (IPN) architecture. Previously, PVA has been modified with methacrylate functions in order to cross-link it by free-radical polymerization. The fibrin network was synthesized by the enzymatic hydrolysis of fibrinogen by thrombin. The resulting self-supported materials simultaneously exhibit the properties of the fibrin hydrogel and those of the synthetic polymer network. Their storage modulus is 50-fold higher than that of the fibrin hydrogel and they are completely rehydratable. These materials are noncytotoxic toward human fibroblast and the fibrin present on the surface of PVAm-based IPNs favors cell development.

The wetting properties of spin-coated films of copolymers based on azobenzene and fluorinated units have been investigated. The copolymers, denoted as poly(Azo-co-AcRf6), have been synthesized by free-radical polymerization of different proportions of acrylate monomers bearing either an azobenzene group or a semifluorinated side chain. The UV-visible spectroscopy analysis of the different spin-coating films through a cycle of UV and visible light irradiation indicates the reversible trans-cis isomerization of azobenzene groups. Simultaneously, atomic force microscopy shows that surface roughness does not exceed 1 nm. Advancing and receding contact angles of water and diiodomethane have been measured before and after UV photoirradiation of the different surfaces. In particular, a decrease in the advancing contact angles has been observed upon trans-cis isomerization of azobenzene groups. Switching variations up to 50° have been evidenced without any introduction of surface nanoroughness. Surface free-energy evaluations have been deduced from these measurements, including dispersive and polar components. The results show that, through surface composition and UV photoirradiation, a large range of surface free-energies can be obtained, from 7 to 46 mN·m(-1).

International audience; Original 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.

International audience; The purpose of this study has been to develop new proton-exchange membranes based on semiinterpenetrating polymer network (semi-IPN) architectures for application in polymer electrolyte fuel cells. A series of semi-IPNs combining a fluorinated hexane network and a linear sulfonated poly(aryl ether ether ketone) (SPEEK) has been obtained by varying the SPEEK content from 50 to 80 wt.%. A telechelic functionalized acrylate oligomer was obtained by acrylation of , -fluorinated hexanediol, while SPEEK was synthesized by polycondensation of sulfonated difluorobenzophenone with the bisphenol 6F. These semi-IPN membranes have been characterized by infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, scanning electron microscopy, and small-angle X-ray scattering. A semi-IPN containing 60 wt.% SPEEK has been tested as a fuel cell membrane.