Ce mémoire rapporte la préparation et l'étude de matériaux hybrides organiques-inorganiques à base de titane où les deux réseaux sont liés par des liaisons titane-carbone stables. Différents précurseurs dans lesquels deux groupes cyclopentadienyltitane sont reliés par des espaceurs variés ont été préparés. Ces espaceurs comprennent des groupes aromatiques et hétéroaromatiques linéaires ainsi que des groupes aromatiques disubstitués par des chaînes alkyle. Ces complexes dimétalliques, où le titane est aussi lié à trois groupes labiles, ont été ensuite hydrolysés dans les conditions du procédé sol-gel pour conduire à des hybrides de classe II. Le réseau organique y est lié au réseau inorganique par des liaisons stables titane-carbone. Ces matériaux sont organisés et leur mode d'organisation dépend de la nature de l'espaceur reliant les groupes cyclopentadienyle. Les espaceurs linéaires conduisent à des matériaux à structure en escalier dans lesquels les ligands sont associés par des liaisons p. La longueur des espaceurs n'a pas d'effet sur cette organisation. Par contre, les matériaux à espaceurs substitués latéralement sont organisés par les chaînes alkyle. La calcination de ces matériaux hybrides sous oxygène conduit à la formation de dioxyde de titane nanoporeux sous forme d'anatase dont la cristallinité et la surface spécifique dépendent de la température de calcination. D'une façon similaire des films de dioxyde de titane de même type sont obtenus par la calcination de films minces d'hybrides préparés par spin-coating. / This work aimed to the preparation of titanium-based organic-inorganic hybrid materials where both networks are linked through stable titanium-carbon bonds. The preparation of various di(cyclopentadienyltitanium) precursors in which various organic groups serve as a bridge between the two cyclopentadienyl groups while each titanium atom is equipped with three hydrolysable groups was first achieved. Then, these complexes were hydrolyzed in a sol-gel process that led to new self-assembled titanium-based class II hybrid materials in which the inorganic network is connected to the organic network through stable titanium-carbon bonds. The mode of organization of the nanostructures depends on the spacer bridging the cyclopentadienyl groups. Linear aromatic spacers led to materials having a stair-like structure in which the organic ligands are arranged via p-stacking. The length of the spacer has a little effect on the organization of the nanostructures. The structure of the materials obtained with spacers endowed with long lateral chains is governed by the side chains. The calcination of these materials under oxygen led to the formation of nanoporous anatase titanium dioxide the crystallinity and surface area of which depend on the calcination temperature. Similarly titanium dioxide thin films were prepared by the calcination of hybrid thin films prepared by spin coating.

Le développement de procédés catalytiques pour la valorisation chimique du dioxyde de carbone (CO2), suscite un intérêt grandissant en termes de chimie du carbone et de développement durable. Les travaux de cette thèse portent sur l’étude de la synthèse de carbonates cycliques à partir du couplage du CO2 avec des époxydes. De nombreux catalyseurs ont été développés dont les sels d’ammoniums fournissant le nucléophile nécessaire pour initier la réaction par ouverture de l’époxyde. Notre projet propose une nouvelle approche qui consiste à augmenter la nucléophilicité du catalyseur via une chimie hôte-invité dans laquelle des récepteurs moléculaires de type cavitands viennent sélectivement encapsuler les cations ammoniums, libérant ainsi l’anion nucléophile pour une meilleure réactivité. Notre système catalytique, testé à 1 bar de CO2, a notamment démontré tout son potentiel par l’activation accrue de sels de tétraméthylammonium initialement inactifs. Des expériences effectuées sous une pression de CO2 de 10 bar, ont permis d'étudier l’influence de la structure des cavitands et de montrer qu’une double activation était possible grâce à la conception de cavitands comportant des fonctions acides de Brönsted et des propriétés d’encapsulation optimales. Une application à la catalyse hétérogène a finalement été initiée par l’immobilisation des ammoniums ou des cavitands sur des supports à base de silice pour profiter des avantages de tels procédés. / The utilization of carbon dioxide (CO2) as a key component in organic transformations has recently drawn much attention as a greener alternative to fossil fuel based resources. The objectives of this work aim at studying the synthesis of cyclic carbonates from the coupling of CO2 with epoxide. Numerous catalysts have been proposed for this reaction among which the ammonium halides providing the nucleophile to initiate the reaction by opening the epoxide. Herein, we propose a new approach based on host-guest chemistry, to improve catalytic reactivity by increasing the nucleophilicity of the halide anion. For this purpose, cavitand molecular receptors able to bind quaternary ammonium ions are used, releasing the anionic nucleophile for the initial epoxide ring-opening reaction. At CO2 atmospheric pressure, our catalytic systems demonstrated a great potential by the dramatic activation of tetramethylammonium halides, whereas when used alone, these catalysts had never shown any activity. The influence of the cavitand structure was investigated through experiments run under 10 bar of CO2 pressure, and revealed that a double activation was possible with cavitand bearing Brönsted acidic hydroxyl functions and optimal recognition properties. The heterogeneization of such catalytic systems was finally studied with the grafting of either ammoniums or cavitands on silica based materials.

La technologie lithium-air à électrolyte aqueux pourrait révolutionner le stockage de l'énergie, mais la protection du lithium métallique par une vitrocéramique conductrice du lithium reste une limitation importante. Cela rend le système plus fragile, limite sa cyclabilité et augmente la chute ohmique. L'objectif de ce travail a été de remplacer cette vitrocéramique par une membrane hybride réalisée par extrusion électro assistée ou electrospinning, qui combine des propriétés d'étanchéité à l'eau, de flexibilité et de conductivité du lithium. La conductivité ionique est apportée par la partie céramique, pour laquelle les matériaux Li1,4Al0,4Ti1,6(PO4)3 (LATP) et Li0,33La0,57TiO3 (LLTO) ont été étudiés. L'étanchéité est assurée par un polymère fluoré. Différentes voies de synthèse des poudres ont été étudiées et comparées en termes de pureté, de microstructure, de surface spécifique et de propriétés électrochimiques. En particulier, des particules de LATP sub-microniques ont été obtenues pour la première fois par chauffage micro-onde, en des temps aussi courts que 2 min. Des membranes ont ensuite été réalisées à partir de suspensions. Dans une seconde approche, un réseau de nanofibres interconnectées et conductrices du lithium a été réalisé par couplage entre la chimie sol-gel et le procédé d'electrospinning. L'imprégnation de ce réseau donne une membrane hybride flexible, conductrice du lithium et étanche à l'eau. Un renforcement mécanique par les fibres inorganiques est observé. Cette approche a été appliquée aux deux matériaux LATP et LLTO. Ce travail ouvre de nombreuses perspectives pour les batteries lithium-air, lithium soufre et lithium-ion. / Aqueous lithium-air batteries could be a revolution in energy storage, but the main limitation is the use of a thick glass-ceramic lithium ionic conductor to isolate the metallic lithium from the aqueous electrolyte. This makes the system more fragile, limits its cyclability and increases ohmic resistance. The aim of this work is to replace the glass-ceramic by a hybrid membrane made by electrospinning, which combines water tightness, flexibility and lithium-ions conductivity. The ionic conductivity is provided by a nanostructured solid electrolyte ceramic: both Li1,4Al0,4Ti1,6(PO4)3 (LATP) and Li0,33La0,57TiO3 (LLTO) were studied. The water tightness is ensured by a fluorinated polymer. Different powders synthesis methods are reported and compared in terms of purity, microstructure, specific surface area and electrochemical properties. Especially, the LATP microwave-assisted synthesis is reported for the first time. Sub-micrometric LATP particles were obtained in times as short as 2 min. The fabrication of hybrid membranes from suspension is then reported. In a second approach, the coupling between sol-gel chemistry and electrospinning made possible the fabrication of a self-standing lithium-conducting network, made of interconnected crystalline nanofibers. After an impregnation step, a flexible, lithium-conducting and watertight hybrid membrane is obtained. A mechanical reinforcement is observed, which is attributed to the inorganic nanofibers. This approach is exposed for both LATP and LLTO solid electrolytes. This work opens new prospects in lithium-air, lithium-sulfur and lithium-ion batteries.

Les nanoparticules d'or de petite taille (< 5 nm) sont des matériaux qui présentent une bonne activité catalytique dans des réactions d'oxydation, et ce dans des conditions relativement douces. Cependant, il est difficile d'obtenir des nanoparticules monodisperses et de taille inférieure à 5 nm. En ce sens, les clusters d'or sont intéressants, car ce sont des composés atomiquement définis avec une formulation propre. Cela signifie que dans un cluster, le nombre d'atomes d'or et de ligands le stabilisant est déterminé. Comme ils peuvent être isolés purs, ils constituent donc une classe de nanoparticules parfaitement monodisperses. Nous nous sommes intéressés, dans le cadre de cette thèse, à la synthèse de clusters d'or et à leur assemblage afin d'avoir des catalyseurs atomiquement définis. Les nanoparticules d'or sont souvent utilisées après dépôt sur un support, résultant en la perte de surface accessible. Nous voulons donc utiliser ces clusters (i) comme espèces moléculaires déposées sur un support et (ii) comme briques moléculaires pour l'assemblage de réseaux tridimensionnels où la porosité permettrait la diffusion des réactifs/produits pour s'affranchir des effets de supports. Notre étude porte donc sur la synthèse de clusters d'or et nous nous sommes également intéressés aux polymères de coordination d'or (I), un intermédiaire de réaction important dans la synthèse de clusters et à ses propriétés photophysiques. Afin d'avoir des clusters avec une fonction externe permettant de les assembler ou de les déposer sur un support, nous avons développé une nouvelle voie de synthèse de clusters stabilisés par des ligands de type thiophénolates para-substitués. Nous avons ainsi isolé de nouveaux clusters stabilisés par des ligands hétérotopiques comme [Au25(SPh-pNH2)17]. Ces composés ont ensuite été déposés sur un support mésoporeux (SBA-15) et utilisés comme catalyseurs dans différentes réactions d'oxydation. Nos résultats montrent que les clusters d'or sont donc des précurseurs moléculaires permettant de préparer des catalyseurs efficaces, ayant une petite taille de particules (1-2 nm) et présentant des activités catalytiques très élevées comparativement aux matériaux de référence / Small gold nanoparticles (< 5 nm) are materials presenting a good catalytic activity in oxidations reactions, especially under soft conditions of temperature and pressure. However, it can be difficult to obtain monodisperse particles with a diameter less than 5 nm. In this sense, gold clusters are interesting, because they are atomically defined compounds, presenting a proper formulation. This means that the number of gold atoms and of stabilizers in the clusters are defined and, as they can be isolated pure, they constitue a novel class of perfectly monodisperse nanomaterials. Therefore, we are interested, in this thesis, in the synthesis and assembly of gold clusters. Indeed, gold nanoparticles are usually deposited on a support, resulting in the loss of accessible area. We therefore wanted to use gold clusters as (i) molecular species deposited on a support and (ii) as building blocks to assemble and organize tridimensional networks where the porosity permits the substrates/products diffusions and avoid the support effects. Our study deals with the synthesis of gold clusters, and we are also interested in the gold (I) coordination polymers, which are important reaction intermediates formed during the clusters synthesis and to its photophysical properties. In order to have clusters presenting external functions enabling their assembly or deposition on a support, we developed a novel synthesis suitable for para-substituted thiophenolates. We managed to isolate new clusters stabilized by heterotopic ligands such as [Au25(SPh-pNH2)17]. Those compounds have been deposited on a mesoporous support and used as oxidative catalysts. Our results show that gold clusters are molecular precursors that permit to prepare effective catalysts with narrow particle size (1-2 nm) and presenting high catalytic activity compared to the one exhibited by reference materials

Cette thèse s’inscrit dans une volonté de décrire l’impact de la température sur des systèmes hybrides et plus particulièrement sur un système or/polymère. L’utilisation et l’étude des propriétés de l’or en couche mince est un sujet d’actualité comme le montre le nombre important de publications chaque année (>6000). Les domaines d’applications sont nombreux en particulier dans les secteurs de l’électronique, du médical ou de l’énergie… De nombreux facteurs peuvent modifier les propriétés physiques (structure, électrique, optique) des assemblages nanométriques. Dans ce travail, nous avons choisi d’étudier l’influence sur les propriétés physiques de l’assemblage de la température du substrat lors du dépôt des couches minces d’or. Dans une première partie, les effets de la température sur la morphologie des surfaces des assemblages seront mis en évidence par une étude statistique d’images AFM. Afin de réaliser cette analyse nous avons développé une nouvelle méthode d’analyse de surface granulaire nommée - l’Interfacial Differential Function. Nous démontrerons l’efficacité de cette méthode statistique vis-à-vis des méthodes existantes en analysant différentes surfaces modèles et, en extrayant les distances caractéristiques (taille de grains, distance inter-grains). La méthode a ensuite été appliquée avec succès à l’étude de l’évolution de la morphologie de films minces d’or déposés sur silicium en fonction de la température du substrat lors du dépôt. Nous avons ainsi pu montrer que, contrairement à ce qui était décrit jusqu’ici dans la littérature, l’augmentation de la rugosité observée lorsque la température de dépôt augmente n’était pas due à une augmentation de la largeur des grains.Dans une seconde partie, nous étudierons l’évolution de la structure interne des assemblages en fonction de la température de dépôt. La forte influence des propriétés thermiques du polymère sur la structure de l’assemblage nanométrique or/polymère a été mise en évidence par réflectivité de rayons X et par microscopie électronique à transmission. La combinaison de la réflectivité de rayons x associée avec la microscopie à force atomique nous a permis de révéler l’évolution avec la température de la structure qui passe d’une structure stratifiée à basse température à une structure plus complexe de type composite avec la présence de polystyrène en surface pour les hautes températures. Dans une dernière partie, l’impact de la température sur les propriétés électriques, optiques des assemblages sera présenté. Le passage d’une surface conductrice à faible température à une surface isolante à haute température sera mis en évidence via une étude originale basée sur une cartographie de résistance électrique réalisée par AFM. Les propriétés d’exaltation optique seront quant à elles présentées à travers une étude par spectroscopie Raman.En conclusion, les résultats de ce travail seront mis en perspectives par rapport à des applications potentielles telles que l’électronique flexible ou la fabrication de capteurs. / This thesis is part of an effort to describe the impact of temperature on hybrid systems and more particularly on a gold/polymer system. The use and study of properties of gold thin film is a timely topic as evidenced by the large number of publications each year (>6000). The fields of applications are numerous especially in areas of electronics, medical or energy… Many factors can modify physical properties (structural, electrical, optical) of nanoscale assemblies. In this work, we have chosen to study the influence on physical properties of the assembly of the substrate temperature during the deposition of thin layers of gold.In the first part, effects of temperature on the surface morphology of the assemblies will become apparent from a statistical study of AFM images. To perform this analysis we have developed a new granular analysis method called IDF – Interfacial Differential Function. We will demonstrate the effectiveness of this statistical approach against the existing methods by analyzing different models and surfaces, by extracting the characteristic distances (grain size, inter-grain distance). The method has been successfully applied to the study by demonstrating changes in the morphology of thin films deposited on silicon versus the temperature of the substrate during deposition. We were able to show that, contrary to what previously described in the literature, the increased roughness observed when the deposition temperature increased, is not due to an increase in the width of the grains.In a second part, we will study the evolution of the internal structure of assemblies based on the deposition temperature. The strong influence of the thermal properties of the polymer structure on the gold/polymer nano-assembly has been shown by X-ray reflectivity and transmission electron microscopy. The combination of x-ray reflectivity associated with the atomic force microscopy has allowed us to reveal the evolution with the temperature of the structure changes from a layered structure at low temperature to a more complex structure of composite type with the presence of polystyrene on the surface for high temperatures.In the last part, the impact of temperature on optical electric properties, assemblies will be presented. The transition from a conductive surface at low temperature to a high temperature insulating surface will be highlighted via an original study based on a mapping of electrical resistance produced by AFM. Optical exaltation properties will be presented through a study by Raman spectroscopy.In conclusion, results of this work will be put in perspective with respect to potential applications such as flexible electronics and fabrication of sensors.

Des complexes à base de palladium (II) ont été appliqués comme catalyseurs pour la réaction d’hydroestérification de l’isosorbide, matériau biosourcé, avec le 1-octène. Dans un premier temps, l’utilisation de liquides ioniques standards a permis l’immobilisation du catalyseur (palladium + phosphine) et la conversion du 1-octène. L’activité catalytique est dépendante de la nature du liquide ionique. Le liquide ionique sulfoné bSmimAPTS a permis l’obtention de conversions élevées, avec des rendements en diesters importants sur trois cycles catalytiques tout en s’affranchissant de l’emploi d’acide paratoluènesulfonique. Le catalyseur (palladium + phosphine sulfonée) est immobilisé dans la phase liquide ionique. La régiosélectivité de la réaction peut être modifiée (85/15 contre 75/25 dans les conditions classiques) avec le remplacement de la TPPTS par une phosphine bidentate sulfonée (XANTPHOS sulfonée). Un système constitué de Pd(OAc)2/APTS/NBu4Br s’est également montré très efficace dans la conversion du 1-octène en diester d’isosorbide mais n’est pas très stable dans le temps (recyclé à deux reprises). Dans un second temps, l’utilisation de charbons actifs commerciaux a permis d’immobiliser le métal (après filtration à froid) tout en conservant une activité catalytique élevée. Il est possible de convertir le 1-octène en substituant l’APTS par un matériau carboné sulfoné (obtenu par voie hydrothermale en une étape entre le saccharose et l’acide sulfurique). Les synthèses, caractérisations et applications d’un matériau carboné nanorépliqué sulfoné de type CMK-3 ont été considérées. Le matériau carboné sulfoné (MC-NR-saccharose-500-SO3H) a permis l’obtention de conversions et de rendements en diesters élevés, avec une sélectivité en large faveur de l’isomère linéaire (rapport l/b=92/8). Une extension à été étudiée avec la synthèse d’un matériau hybride sulfoné (MCSi 10.4-SO3H) et a également conduit à une activité catalytique élevée avec une sélectivité importante en isomère linéaire (rapport l/b=92/8). Des tests avec des matériaux acides contrôles (résine commerciale sulfonée et silice sulfonée) ont été réalisés. / Complex based on palladium salt (II) were applied as catalysts for the hydroesterification of isosorbide, a biobased molecule, with 1-octen. First, the use of standard ionic liquids permits the immobilization of the catalyst (palladium + phosphine) and the conversion of 1-octen. The catalytic activity is dependent on the nature of the ionic liquid. The sulfonated ionic liquid bSmimAPTS permit the obtention of high conversions, with important yield in diester during three catalytic cycles, and avoid the use of paratoluenesulfonic acid. The catalyst (palladium + sulfonated phopshine) is immobilized in the ionic liquid phase. The regioselctivity of the reaction can be changed with the replacement of the TPPTS by a sulfonated bidentate phosphine (XANTPHOS, l/b ratio= 85/15 against 75/25 in classical condition). A system containing Pd(OAc)2/APTS/NBu4Br proved also highly effective in the conversion of 1-octen but it was not very stable over time (recycled just two times). Secondly, the use of commercial activated carbons has immobilized the palladium after cold filtration while maintaining high catalytic activity. It’s possible to convert the 1-octen using a sulfonted carbonaceous material (obtained by hydrothermally condition in one step between sucrose en sulfuric acid). Synthesis, characterization and applications of a sulfonated nanoreplicated carbonaceous material, as CMK-3, were considered. This one (MC-NR-saccharose-500(SO3H) permit the obtention of high conversions and high yields of diesters, with a selectivity in favor of the linear isomer (l/b ratio= 92/8). An extension was studied with the synthesis of a sulfonated hybrid material (MCSi 10.4-SO3H) and also results in high conversion and high selectivity in linear isomer (l/b ratio= 92/8). Tests with acidics materials controls (sulfonated commercial resin and sulfonated silica) were performed.

<p>U ovom radu vr&scaron;ena su istraživanja u cilju razvoja novih postupaka sinteze za nekoliko vrsta polimernih mreža i hibridnih biopolimernih materijala za specijalne primene. Cilj je bio da se razvije novi postupak sinteze rotaksana na bazi poli(etilen glikola) i &beta;-ciklodekstrina kaoprekursora mreža. Dobijeni prekursori mreža iskori&scaron;ćeni su za sintezu topolo&scaron;kih gelova koji su umreženi preko hidroksilnih grupa ciklodekstrinskih prstena. Analiziran je i uticaj količine umreživača, odnosno gustine umreženja, na svojstva bubrenja. Proučavan je i uticaj nanopunila na svojstva modelnih epoksi mreža na bazi bisfenola A i poli(oksi propilen) diamina. Kao punila kori&scaron;ćene su nanočestice nemodifikovanog i povr&scaron;inski modifikovanog titanijum(IV)oksida (TiO₂). Dinamičko-mehaničkom analizom potvrđen je ojačavajući efekat punila. Razvijen je postupak sinteze poli(D,L-laktida) u mikrotalasnom polju, čime je drastično smanjeno vreme polimerizacije (sa 150 sati na 15 minuta) u odnosu na klasičnu termosintezu. Sintezom poli(laktida) kao i kopolimera poli(laktida) sa biorazgradivim monomerima (na osnovu obnovljivih sirovina) dobijeni su materijali izuzetnih ekolo&scaron;kih svojstava. Poli(laktid) se odlikuje veoma dobrim mehaničkim svojstvima i biorazgradivo&scaron;ću, dok je blok-kopolimerizacijom sa drugim biorazgradivim monomerima vr&scaron;ena sinteza termoplastičnih poliestara. Variranje dužine segmenata je ostvareno sintezom adekvatnih oligomera kao prekursora za kopolimerizaciju. Vr&scaron;eno je projektovanje sirovinskog sastava segmentiranih elastomera kod kojih postojanje mekih i tvrdih segmenata ima za posledicu mikrofaznu separaciju faza &scaron;to u toku eksploatacije utiče na mehanička svojstva i mogućnost III razgradnje. Na taj način dobijeni su elastomerni materijali željenih svojstava. Metodama FTIC i 1H NMR spektroskopijom potvrđena je pretpostavljena struktura segmenata i finalnih termoplastičnih poliestara. Analizom molskih masa poliestara metodama gel propusne hromatografije, viskozimetrije i osmometrije napona pare, potvrđena je izuzetna kontrola reakcija polimerizacije i uspe&scaron;nost primenjenih metoda sinteze. Analiza toplotnih svojstava blok poliestara diferencijalno skenirajućom kalorimetrijom je pokazala da zbog neme&scaron;ljivosti faza, tvrdih i mekih segmenata, finalni blok poliestri mogu da pokažu razlike u temperaturama faznih transformacija u zavisnosti od dužine i udela segmenata. Termogravimetrijskom analizom je potvrđen uticaj dužine segmenata i faznog razdvajanja na toplotna svojstva termoplastičnih poliestara. Očekuje se da će sintetisani materijali biti podesni za primene u inženjerstvu tkiva, a posebno kao materijali za kontrolisano otpu&scaron;tanje lekova.</p> / <p>The primary goal of the work described in this thesis was to develop new methods for the<br />synthesis of polymer networks and hybrid biopolymers for special applications. The purpose was a development of synthesis procedure for the preparation of rotaxane based on poly(ethylene glycol) and &beta;-cyclodextrin, as network precursors. These network precursors were then cross-linked through hydroxy groups on cyclodextrine rings. Polyrotaxanes are intermediary products in the synthesis of topological gels and they are formed by the insertion of the linear polymer chains of poly(ethylene oxide) into the &beta;-CD cavities. In this work polyrotaxanes from acetylated-&beta;-CD and poly(ethylene oxide) were synthesized. The influence of crosslinker contents, and crosslink density on swelling properties was investigated. The influence of synthesis parameters and filler modification on reactions and final properties of organic-inorganic hybrid materials based on epoxy resin and an organically modified titanium(IV)oxide (TiO2) was investigated. Dynamic-mechanical analysis was used to determine reinforcement effect of nanofiller on the epoxy resin properties. The aim of this work was the investigation of microwave irradiation on the polymerization of D,L-lactide. It was found that if heating is carried out in the microwave field polymerization time of D,Llactide rapidly decreases from 150 hours to 15 minutes. Environmentally friendly materials were obtained from poly(lactide) and copolymers of poly(lactide) and monomers based on renewable resources. Poly(lactide) is biocompatible and biodegradable polymer with high stretching and low extension capacities. It has been used for the production of orthopedic fraction fixators and sutures surgery. Poly(lactide) was used for thermoplastic polyester (TPE) synthesis. Most thermoplastic polyesters derive their properties from segmented or block structures which are achieved by alternating hard and soft segments. FT-IR and 1H NMR spectroscopy were confirmed the assumed structure of segments and final thermoplastic polyesters. Since the properties of these materials strongly depend on the degree of phase separation, the influence of the lenghts of soft and hard segment on final properties of obtained TPEs was studied. Analysis of molecular mass of these polyesters by gel permeation chromatography, vapor pressure osmometry and viscozimetric analysis confirmed that good control of polymerization was achieved and that synthesis methods were successful. Thermal properties were characterized by means of differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TGA). Phase separation had strong influences on thermal properties of obtained TPEs. DCS measurements showed that due to poor mixability of hard and soft segments, final block polyesters could have different temperatures of phase transitions depending on the length of the segments. Thermal degradation and the influence of phase separation on thermal stability of segmented thermoplastic polyesters were confirmed by nonisothermal analysis, using thermogravimetric analysis. It is expected that synthesized materials will be suitable for tissue engineering and as drug carriers.</p>

L’administration d’aliments fonctionnels contenant des cellules probiotiques est une des voies de rétablissement de l'équilibre du microbiota. Pour assurer la protection des probiotiques pendant la transformation des aliments et le passage gastro-intestinal, l'encapsulation est essentielle. Nous proposons ici des supports hybrides à base de silice en tant que nouveaux systèmes d’encapsulation de probiotiques. Lactobacillus rhamnosus GG (LGG) a été choisi comme modèle de bactéries probiotiques et l'alginate comme polymère prébiotique. Deux types de supports ont été préparés, soit par émulsification, soit par électrospraying: (i) des billes hybrides de 10-30 μm dans lesquelles les bactéries étaient en contact direct avec un mélange d'alginate et de silice et (ii) des particules cœur-couronne de 200-600 μm dans lesquelles les bactéries sont d'abord encapsulées dans un gel d'alginate, puis recouvertes d'une couche de silice. La viabilité des LGG a été efficacement maintenue seulement dans les particules cœur-couronne, dans lesquelles LGG n’ont pas était directement exposées à la silice. Ces prototypes cargo ont permis la protection de LGG pendant le stockage dans la bière ou le jus de pomme, ainsi que pendant le passage à travers le tractus gastro-intestinal. En outre, les LGG libérées dans un écosystème fécal se sont multipliées au détriment des autres membres de la communauté de Lactobacilli. Cette étude offre donc une preuve de concept quant à la potentialité des systèmes hybrides silice/biopolymère pour l'administration orale de bactéries probiotiques / One way to reestablish the microbiota equilibrium is to administrate a functional food containing probiotic cells. To insure protection of the living matter during the food processing and the gastrointestinal passage, encapsulation is essential. Herein we propose silica-based hybrid carriers as new probiotic delivery systems. Lactobacillus rhamnosus GG (LGG) was chosen as a model probiotic bacteria and alginate as prebiotic polymer. Two types of carriers were prepared either by emulsification or by electrospraying: (i) hybrid beads of 10-30 m in which the bacteria was in direct contact with a mixture of alginate and silica and (ii) core-shell beads of 200-600 m in which the bacteria are first embedded in an aqueous core of alginate, then coated with a silica shell. The viability of LGG was efficiently maintained only in core-shell particles, in which LGG was not directly exposed to silica. Those core-shell prototype carriers allowed the protection of LGG during storage in beer or apple juice, and during the passage through the gastrointestinal tract. Additionally the LGG released in the colon outcompete other members of the Lactobacilli community and it was able to thrive within a fecal ecosystem. This study offers thus a proof of concept for the potential use of hybrid silica/biopolymer systems in oral delivery of probiotic bacteria

<p>Microparticles have been investigated not only as feedstock spherical or amorphous bulk materials used for shape molding, but also as agents that can perform work in the micron scale. The fabrication of microparticles with active properties of self-propulsion, self-assembly, and mobility with enhanced mechanical, thermal, and chemical properties is of particular interest for emerging technologies such as drug delivery, micro-robotics, micro energy generation/harvesting, and MEMS. Conventional fabrication methods can produce several complex particle shapes in one fabrication session or hundreds of spheroid shaped particles per second. Innovative techniques, as flow lithography, have demonstrated control over particle form and composition for continuous fabrication cycles. In recent years predefined shape polymer microparticles have been fabricated as well as ceramic microparticles through suspension processing with these set of techniques. Even though ceramic materials have been fabricated, there is still a strong need to increment the palette of available materials to be processed via flow lithography. We have pioneered the production of shaped ceramic microparticles by Stop-Flow Lithography (SFL) using preceramic polymers, providing control of particle size and shape in the range of 1 – 1000 μm. The principal arranged technique (SFL) combines aspects of PDMS-based microfluidics and photolithography for the continuous cyclable fabrication of microparticles with predefined shapes. The PDMS microchannel devices used were fabricated with vinyl film molds in a laminar hood avoiding the need for a cleanroom, procedure that reduced fabrication costs. After a fabrication session, the preceramic polymer microparticles were collected, washed, and dried before entering an inert atmosphere furnace for pyrolysis. Additionally, by treating the material initially as liquid polymer, special properties can be added by converting it into an emulsion or a suspension. Microparticles were functionalized by introducing porosity and magnetic nanoparticles in the preceramic polymer matrix. The porous characteristic of a particle leads to an increase in surface area, allowing the particle to be infiltrated with a catalyzer or act as a chemical/physical carrier, and the magnetic behavior of the particles allows a controllable trajectory with defined external magnetic fields. These two properties can be used to fabricate bifunctional microparticles to serve as drug carriers through human arteries and veins for drug delivery purposes. We successfully fabricated solid and functional ceramic microparticles in the 10 – 50 μm range with predefined shapes as hexagons, gears, triangles, and ovals. This system is an economical route to fabricate functional defined shape particles that can serve as microrobots to perform tasks in liquid media.</p>

<p>Naturally-occurring biological materials with stiff mineralized reinforcement embedded in a ductile matrix are commonly known to achieve excellent balance between stiffness, strength and ductility. Interestingly, nature offers a broad diversity of architectural motifs, exemplify the multitude of ways in which exceptional mechanical properties can be achieved. Such diversity is the source of bio-inspiration and its translation to synthetic material systems. In particular, the helicoid and the “brick and mortar” architectured materials are two key architectural motifs we are going to study and to synthesize new bio-inspired materials. </p> <p>Due to geometry mismatch(misorientation) and incompatibilities of mechanical properties between fiber and matrix materials, it is acknowledged that misoriented stiff fibers would rotate in compliant matrix beneath uniaxial deformation. However, the role of fiber reorientation inside the flexible matrix of helicoid composites on their mechanical behaviors have not yet been extensively investigated. In the present project, fiber reorientation values of single misoriented laminae, mono-balanced laminates and helicoid architectures under uniaxial tensile are calculated and compared. In the present work, we introduce a Discontinuous Fiber Helicoid (DFH) composite inspired by both the helicoid microstructure in the cuticle of mantis shrimp and the nacreous architecture of the red abalone shell. We employ 3D printed specimens, analytical models and finite element models to analyze and quantify in-plane fiber reorientation in helicoid architectures with different geometrical features. We also introduce additional architectures, i.e., single unidirectional lamina and mono-balanced architectures, for comparison purposes. Compared with associated mono-balanced architectures, helicoid architectures exhibit less fiber reorientation values and lower values of strain stiffening. The explanation for this difference is addressed in terms of the measured in-plane deformation, due to uniaxial tensile of the laminae, correlated to lamina misorientation with respect to the loading direction and lay-up sequence.</p> <p>In addition to fiber, rod-like, reinforced laminate, platelet reinforced composite materials, “brick and mortar” architectures, are going to be discussed as well, since it can provide in-plane isotropic behavior on elastic modulus that helicoid architecture can offer as well, but with different geometries of reinforcement. Previous “brick and mortar” models available in the literature have provided insightful information on how these structures promote certain mechanisms that lead to significant improvement in toughness without sacrificing strength. In this work, we present a detailed comparative analysis that looks at the three-dimensional geometries of the platelet-like and rod-like structures. However, most of these previous analyses have been focused on two-dimensional representations. We 3D print and test rod-like and tablet-like architectures and analyze the results employing a computational and analytical micromechanical model under a dimensional analysis framework. In particular, we focus on the stiffness, strength and toughness of the resulting structures. It is revealed that besides volume fraction and aspect ratio of reinforcement, the effective shear and tension area in the matrix governs the mechanical behavior as well. In turns, this leads to the conclusion that rod-like microstructures exhibit better performance than tablet-like microstructures when the architecture is subjected to uniaxial load. However, rod-like microstructures tend to be much weaker and brittle in the transverse direction. On the other hand, tablet-like architectures tend to be a much better choice for situations where biaxial load is expected.</p> <p>Through varying the geometry of reinforcement and changing the orientation of reinforcement, different architectural motifs can promote in-plane mechanical properties, such as strain stiffening under uniaxial tensile, strength and toughness under biaxial tensile loading. On the other hand, the various out-of-plane orientation of the reinforcement leads to functionally graded effective indentation stiffness. The external layer of nacre shell is composed of calcite prisms with graded orientation from surface to interior. This orientation gradient leads to functionally graded Young’s modulus, which is confirmed to have higher fracture resistance than homogenous materials under mode I fracture loading act.</p> <p>Similar as graded prism orientation in calcite layer of nacre, the helicoid architecture found in nature exhibits gradients on geometrical parameters as well. The pitch distance of helicoid architecture is found to be functionally graded through the thickness of biological materials, including the dactyl club of mantis shrimp and the fish scale of coelacanth. This can be partially explained by the long-term evolution and selection of living organisms to create high performance biological materials from limited physical, chemical and geometrical elements. This naturally “design” procedure can provide us a spectrum of design motifs on architectural materials. </p> <p>In the present work, linear gradient on pitch distance of helicoid architectures, denoted by functionally graded helicoid (FGH), is chose to be the initial pathway to understand the functionality of graded pitch distance, associated with changing pitch angle. Three-point bending on short beam and low-velocity impact tests are employed in FEA to analyze the mechanical properties of composite materials simultaneously. Both static(three-point bending) and dynamic(low-velocity impact) tests reveal that FGH with pitch angle increasing from surface to interior can provide multiple superior properties at the same time, such as peak load and toughness, while the helicoid architectures with constant pitch angle can only provide one competitive property at one time. Specifically, helicoid architectures with smaller pitch angle, such as 15-degree, show higher values on toughness, but less competitive peak load under static three-point bending loading condition, while helicoid architectures with middle pitch angle, larger than or equal to 22.5-degree and smaller than 45-degree, exhibit less value of toughness, but higher peak load. The explanation on this trend and the benefits of FGH is addressed by analyzing the transverse shear stresses distribution through the thickness in FEA, combined with analytical prediction. In low-velocity impact tests, the projected delamination area of helicoid architectures is observed to increase when the pitch angle is decreasing. Besides, laminates with specific pitch angles, such as 45-degree, classical quasi-isotropic laminate, 60-degree, specific angle ply, and 90-degree, cross-ply, are designed to compare with helicoid architectures and FGH.</p>