Odile Fichet

Development of a Lithium Air Rechargeable Battery

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.

Fibrin-polyethylene oxide interpenetrating polymer networks: new self-supported biomaterials combining the properties of both protein gel and synthetic polymer.

Interpenetrating polymer network (IPN) architectures were conceived to improve the mechanical properties of a fibrin gel. Conditions allowing an enzymatic reaction to create one of the two networks in IPN architecture were included in the synthesis pathway. Two IPN series were carried out, starting from two polyethylene oxide (PEO) network precursors leading to different cross-linking densities of the PEO phase. The fibrin concentration varied from 5 to 20 wt.% in each series. The behavior of these materials during dehydration/hydration cycles was also studied. The mechanical properties of the resulting IPN were characterized in the wet and dry states. These self-supported biomaterials combine the properties of both a protein gel and a synthetic polymer. Finally, cells were grown on PEO/fibrin IPN, indicating that they are non-cytotoxic.

Poly(azobenzene acrylate-co-fluorinated acrylate) spin-coated films: influence of the composition on the photo-controlled wettability.

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).

Interfacial polymerization of a 3,4-ethylenedioxythiophene derivative using Langmuir–Blodgett technique. Spectroscopic and electrochemical characterizations

Abstract 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.

Synthesis and characterization of photosensitive cinnamate-modified cellulose acetate butyrate spin-coated or network derivatives

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.

Self-supported fibrin-polyvinyl alcohol interpenetrating polymer networks: an easily handled and rehydratable biomaterial.

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.

Contribution toward comprehension of contact angle values on single polydimethylsiloxane and poly(ethylene oxide) polymer networks.

The large application ranges of polydimethylsiloxane (PDMS) and poly(ethylene oxide) (PEO) based materials justify the importance of controlling polymer surface properties including morphology and wettability behavior. However, it appears that the reported contact angle values of PDMS surfaces show significant scattering which cannot always be interpreted in terms of sole chemical data. In addition, few values are reported concerning pure PEO surfaces, since the polymer generally swells in the presence of water. Thus, in order to correlate surface properties with sample preparation, several single PDMS and PEO polymer networks were synthesized with varying cross-linkers and different cross-linking densities. First, the sample surface topography was systematically analyzed by atomic force microscopy (AFM). It was proven that the removal process of the polymer film from the mold plays a significant role in surface topography according to the vitreous or rubbery state of the given polymer network at room temperature irrespective of mold surface treatment. AFM-scale smooth surfaces can be obtained for all the samples by removing them systematically from the mold at a temperature below the α-relaxation temperature. Dynamic water contact angles were then measured and the values analyzed as a function of cross-linker nature and cross-linking density.

Sum-Frequency Generation Spectroscopy of Cinnamate Modified Cellulosic Polymer at the Air–Water Interface

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.

Paper strengthening by polyaminoalkylalkoxysilane copolymer networks applied by spray or immersion: a model study

Abstract Two di-alkoxysilanes, with (AMDES, aminopropylmethyldiethoxysilane) or without (DMDES, dimethyldiethoxysilane) an amine function, and a tri-alkoxy aminosilane (APTES, aminopropyltriethoxysilane) 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.

Evaluation of Fibrin-Based Interpenetrating Polymer Networks as Potential Biomaterials for Tissue Engineering

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.