Cette thèse s'inscrit dans le cadre d'un projet de l'Agence National de Recherche (ANR) dans lequel participent deux sociétés et deux laboratoires universitaires. L'objectif de ce projet consiste à améliorer les propriétés mécaniques (résistance à l'abrasion) et thermiques (température de dégradation) de revêtements fluorés antiadhésifs en y intégrant des nanoparticules de silice. Or, la silice est une charge hydrophile qui se disperse difficilement dans une matrice fluorée. C'est pourquoi nous avons envisagé de modifier sa surface avec des réactifs fluorés, et la nature des divers précurseurs a une influence sur l'amélioration de la dispersion des nanoparticules. Ainsi, nous avons, dans un premier chapitre, étudié la miscibilité et la compatibilité des polymères fluorés entre eux. Les polymères fluorés sont réputés pour leur inertie chimique, hydrophobie et leurs propriétés thermiques très avantageuses. Mais les très bonnes propriétés des polymères fluorés entraînant parfois des difficultés de mise en œuvre, nous avons choisi de travailler avec deux copolymères fluorés, le poly(TFE-co-HFP), un copolymère statistique à base de tétrafluoroéthylène (TFE, -CF2-CF2-) et d'hexafluoropropène (HFP, -CF(CF3)-CF2-) voisin du PTFE utilisé pour les revêtements, et le poly(VDF-co-HFP), un copolymère composé de fluorure de vinylidène (VDF, -CH2-CF2) et d'hexafluoropropène. Ils présentent de bonnes propriétés et sont faciles à employer à l'état fondu de par leurs faibles températures de fusion (respectivement de 140 et 275°C pour le poly(VDF-co-HFP) et le poly(TFE-co-HFP)). Des mélanges binaires à l'état fondu ont été réalisés puis caractérisés entre ces deux copolymères semi-cristallins mais également avec un polyéther fluoré, composé de plusieurs unités d'oxyde d'hexafluoropropène (HFPO, -CF(CF3)CF2O-) totalement amorphe. Les résultats obtenus suite à ces mélanges ont indiqué les trois types de précurseurs fluorés à employer lors des modifications de surface et ce en fonction de la matrice fluorée : composés à base de TFE (-CF2-CF2-), de VDF (-CH2-CF2-) et de l'HFPO (-CF(CF3)CF2O-). Ainsi, le second chapitre est consacré aux stratégies de synthèse de ces précurseurs fluorés contenant des motifs VDF et HFPO. Deux méthodes de polymérisation ont été réalisées : 1) La polymérisation radicalaire par transfert d'iode (ITP) du VDF conduisant à CnF2n+1-[CH2-CF2]m-I ; 2) La polymérisation anionique par ouverture de cycle de l'HFPO permettant la synthèse C3F7O-[CF(CF3)CF2O]-CF(CF3)-COX avec X : groupements fonctionnels. Ces produits ont été caractérisés par spectroscopies RMN du 19F et du 1H, IR, GPC, DRX, ATG et DSC. Les oligomères du TFE (CnF2n+1-I ou CnF2n+1-C2H4-SH avec n= 4 ou 6) n'ont pas été préparés du fait des risques encourus lors de la manipulation du TFE (gaz explosif). Après leurs synthèses, fonctionnalisations et caractérisations, nous les avons greffés à la surface de silices submicroniques. La principale méthode de greffage employé est le « grafting onto » qui permet de modifier la surface des particules inorganiques avec des macromolécules (oligomères ou polymères) et le troisième chapitre présente trois méthodes de greffage : 1) L'addition radicalaire de RFI ou RFC2H4SH sur une double liaison (vinylique ou allylique) ; 2) La condensation d'un oligomère à base d'HFPO fonctionnalisé ester méthylique sur une silice possédant des fonctions amine ; 3) La méthode la plus communément, utilisée l'hydrolyse-condensation, à partir d'oligo(HFPO) fonctionnalisés alkoxysilane. Les méthodes d'analyses employées afin de caractériser ces nanohybrides fluorés sont les spectroscopies RMN 1H et 29Si à l'état solide, IR, les analyses élémentaires et thermogravimétriques. Nous avons utilisé ces différentes stratégie de modifications de surface afin d'obtenir une large gamme de silices modifiées avec des groupements fluorés tout en tenant compte de la miscibilité des chaînes fluorées entre elles (Chapitre 1). / This thesis is part of a project of the National Research Agency (ANR) which involved two companies and two university laboratories. The objective of this project is to improve the mechanical properties (abrasion resistance) and thermal (degradation temperature) nonstick fluorinated coatings by incorporating silica nanoparticles. However, silica is a hydrophilic filler which is hardly dispersed in a fluoridated matrix. Therefore, we planned to modify its surface with fluorinated reagents, and the nature of various precursors has an influence on improving the nanoparticles dispersion. Thus, we, as a first chapter, studied the miscibility and compatibility of the fluoropolymers. Fluoropolymers are known for their very attractive properties like chemical inertness, hydrophobicity and thermal. But these very good properties of fluoropolymers sometimes cause difficulties application, we chose to work with two fluorinated copolymers, poly (TFE-co-HFP), a copolymer based on tetrafluoroethylene (TFE,-CF2-CF2-) and hexafluoropropylene (HFP,-CF(CF3)-CF2-) neighbor of PTFE used for coatings, and poly (VDF-co-HFP), a copolymer composed of vinylidene fluoride (VDF, -CH2-CF2) and hexafluoropropylene. They have good properties and are easy to use in blend due to their low melting temperatures (140 and 275° C for poly (VDF-co-HFP) and poly (TFE-co-HFP), respectively). Blends have been realized and characterized between two semi-crystalline copolymers but also with a fluorinated polyether composed of several units of hexafluoropropylene oxide (HFPO,-CF(CF3)CF2O-) which is completely amorphous. The results obtained from these blends indicated that the three types of precursors can be used for fluorinated surface modifications and in function of the fluoropolymer : compounds are based on TFE (-CF2-CF2-), VDF (-CH2-CF2-) and HFPO (-CF(CF3)CF2O-). Thus, in the second chapter, the synthesis of these fluorinated precursors containing VDF and HFPO units are shown for this, two polymerization methods were carried out : 1) The iodine transfer polymerization (ITP) of VDF ; 2) The anionic polymerization by ring opening of HFPO. These products were characterized by 19F and 1H NMR spectroscopy, FTIR, GPC, XRD, TGA and DSC. Oligomers of the TFE (CnF2n+1-I or CnF2n+1-C2H4-SH with n = 4 or 6) have not been prepared because of the risks incurred during the handling of TFE (explosive gas). After their synthesis, functionalization and characterization, we have grafted them on the surface of silica nanoparticles. The main method used is the "grafting onto" which allows to modify the surface of inorganic particles with macromolecules (oligomers or polymers) and the third chapter presents three methods of grafting : 1) The radical addition of RFI and/or RFC2H4SH on a double bond (vinyl or allyl) ; 2) The condensation of an oligomer based HFPO functionalized methyl ester on a silica with amine functions ; 3) The most commonly used hydrolysis-condensation, using oligo (HFPO) functionalized alkoxysilane. The analysis methods used to characterize these fluorinated nanohybrids are the 1H and 29Si solid state NMR, FTIR, elemental and thermogravimetric analysis. We used these different surface modification to obtain a wide range of modified silica with fluorinated groups. After their characterization, these fluorinated silica are introduced by blend into two fluorinated matrices poly (VDF-co-HFP) and poly (TFE-co-HFP). The fourth is dedicated to the study of nanocomposite poly (VDF-co-HFP) / silica. Initially, a state of the art is presented as this type of composite has been widely discussed in the literature contrary to nanocomposites poly (VDF-co-HFP) or poly (TFE-co-HFP) with fluorinated nanoparticles.

"Il ya beaucoup de place vers le bas!", ait déclaré Richard Feynman dans son discours sur les nanotechnologies en 1959, ouvrant un nouveau monde de la science et de la technologie! L'idée d'utiliser des nanoparticules afin d'améliorer les propriétés diélectriques des polymères qui étaient déjà en cours d'utilisation a suscité l'intérêt des chercheurs dans les deux dernières décennies. Nanocharges tels que la silice, l'alumine, l dioxyde de titan, etc, mais aussi des particules plus grosses comme les argiles ou les nanotubes de carbone ont été mélangés avec les polymères «classiques» afin d'améliorer les propriétés du polyéthylène, des résines époxy, de polypropylène, etc.De nos jours, le rendement de conversion d'énergie de générateurs électriques est limitée par des problèmes thermiques et électriques, limitations étant surtout liées à la qualité des rubans isolants appliqués sur les barres en cuivre. En conséquence, des rubans isolants innovants basés sur des de matériaux nanostructurés ont été envisagés pour augmenter le rendement énergétique des alternateurs et le but de ce travail est d'étudier ces matériaux innovants et de comparer leurs propriétés avec celles des matériaux déjà utilisés, afin d'aider à choisir le meilleur matériau composite pour les futurs rubans. Après une brève introduction sur le contexte de ce travail, on a présenté bref état de l'art les propriétés des polymères époxy, avec un débat sur les propriétés électriques de la matrice polymère choisie (résine époxyde), ses propriétés chimiques et thermiques. Ensuite, les nanocharges choisies et leurs propriétés spécifiques sont présentés, en discutant les différentes étapes du procédé de fabrication, aussi qu'un débat sur les phénomènes qui apparaissent à l'échelle nanométrique et leur éventuelle influence sur les propriétés du matériau composite fini.Différents groupes de matériaux composites à base d'époxy remplis de silice nanométrique, argile organique ou de nitrure de bore sont analysés dans ce travail. Afin de caractériser et interpréter leurs propriétés, plusieurs outils ont été utilisés: la microscopie imagerie, la caractérisation thermique ainsi que les méthodes d'investigation à fort ou faible champ électrique. Leur caractéristiques sont ressemblés et différents observations sur des propriétés «générales» ou «spécifiques» des matériaux composites ont été observés et discutés par rapport à l'influence du type de charge utilisée, de son traitement ou de son poids total sont débattues.Enfin, un modèle numérique basé sure une généralisation de la loi des mélanges sera utilisée afin de prédire la réponse diélectrique des matériaux composites ainsi que les paramètres (taille, permittivité) de l'interphase, «l'ingrédient« magique du mélange matrice de remplissage. Le modèle présenté nous a permis de donner un lien entre les différents matériaux et de valider les résultats obtenus expérimentalement. Une approche par éléments finis est utilisée.Ce manuscrit s'achève par des conclusions sur le travail présenté et il laisse entrevoir les perspectives dans l'analyse complexe des polymères nanocomposites . / “There's plenty of room of the bottom!” said Richard Feynman in his talk on top-down nanotechnology in 1959, bringing into the spot light a new world of science and technology ! The idea of using nanoparticles in order to improve the dielectric properties of the polymers that were already in use attracted the interest of researchers for the last two decades. Nanofillers such as silica, alumina, titania etc, but also larger particles such as clays or carbon nanotubes were mixed with the “classic” polymers in order to improve the properties of polyethylene, epoxy resins, polypropylene etc. Since nowadays the energy conversion efficiency of electrical generators is restricted by thermal and electrical issues, these limitations can be related to the electrical insulator tapes themselves. Thus, innovative insulating tapes based on nanostructured material scenarios to address the energy saving concern are intended and the purpose of this work is to investigate these innovative materials and to compare their properties with those of the materials already in use, in order to help choosing the best composite material for the future tapes.This works begins with a state of the art regarding the properties of epoxy polymers. Their chemical, thermal and dielectric properties are presented. Afterwards, the chosen fillers and their specific properties are presented. The influence of the chosen fillers as well as different steps of the nanocomposite materials manufacturing process are presented and the discussion ends with a debate on the phenomena appearing at the nanometric scale and their possible influence on the properties of the finite composite material .Different materials groups of epoxy based composites filled with nanometric silica, organoclay or boron nitride are analyzed afterwards. In order to characterize and interpret their properties, several tools were used: imaging microscopy, thermal characterization as well as high and low electric field investigation methods. A debate trying to distinguish between so called “general” or “specific” behavior of the composite materials with respect to the normal, unfilled polymer is also presented. The influence of the type of filler, its treatment or its weight total percentage will be are chosen as comparison criteria. Finally, a numerical model based on Finite Element Method approximation was used in order to predict the dielectric response of the composite materials as well as the specific parameters (size, permittivity) of the interphase, the magic “ingredient” of the matrix-filler mix. The presented model allowed us to give a connection between the different materials and validate the experimentally obtained results. This manuscript ends with conclusions on the presented work and suggests possible future works in the complex analysis of polymer nanocomposites.

La morphologie et les propriétés de sorption d’eau et d’éthanol de films extrudés minces de polyamide 6 ont été étudiées pour différentes conditions de mise en oeuvre (température de chill roll (TCR) de 50 et 125°C et taux d’étirage compris entre x et y). L’influence de l’ajout de faibles taux de nanocharges lamellaires (montmorillonite (MMT) ou phosphate de Zirconium (ZrP)) a également été évaluée. L’étirage n’a, dans la gamme étudiée, aucun effet sur la morphologie et les propriétés de sorption des films. Les films de PA6 préparés à une température de chill roll de 50°C présentent en revanche une proportion de phase cristalline g plus faible que les films préparés à une TCR de 125°C. L’épaisseur des lamelles cristallines y est plus fine et la mobilité des chaînes de la phase amorphe y est réduite. L’ajout de faibles taux de montmorillonite à une TCR de 50°C modifie significativement la mobilité des chaînes de la phase amorphe, les proportions des phases cristallines a et g et l’orientation des lamelles cristallines, contrairement à une TCR de 125°C où l’impact de la MMT n’a été observé qu’au niveau de l’orientation de la phase cristalline g. Les mécanismes de sorption de vapeur d’eau et d’éthanol ont été étudiés pour l’ensemble des films. Les isothermes de sorption ont été modélisées afin d’étudier plus particulièrement les phénomènes d’agrégation observés à haute activité. Une modélisation des courbes cinétiques a également été proposée sur la base de l’approche de Berens et Hopfenberg. La confrontation des données thermodynamiques et cinétiques de sorption et des paramètres morphologiques caractéristiques des matériaux a permis de conclure à un rôle prépondérant des interfaces entre zone amorphe et zone cristalline sur le transport / The morphology and water and ethanol sorption properties of thin films made of polyamide 6 were studied in relation to different transformation conditions, namely chill roll temperature (TCR) (50 and 125°C) and stretching ratio (between 6 and 10.8). The influence of nanofillers (montmorillonite (MMT) and zirconium phosphate (ZrP)) was also investigated. It was observed that stretching has no influence on neither the morphology nor the sorption properties in the studied range. In contrast unfilled films prepared at a chill roll temperature of 50°C have a lower amount of g crystalline phase, thinner cristalline lamellae and reduced amorphous phase mobility than films prepared at a chill roll temperature of 125°C. Adding low amounts of MMT at a TCR of 50°C has a remarkable impact on chain mobility, a and g crystalline phase fractions and lamellar orientation whereas the nanoparticules added at a TCR of 125°C only affect the crystalline orientation. Vapor sorption mechanisms were studied for both filled and unfilled films. The sorption isotherm curves were modelled to obtain a deeply understanding of the aggregation phenomena observed at high activity. Modelling of the kinetics was proposed according to Berens and Hopfenberg approach. Coupling the thermodynamics and kinetics of sorption with the morphological data leads to the conclusion that the interfaces between the amorphous and crystalline domains play a critical role on transport properties

Cette thèse développe la synthèse contrôlée et la purification de nanoparticules d’or hybrides, AuNPs stabilisées par des thiols organiques modulant leurs propriétés de surface. Les applications visent la catalyse et le domaine biomédical, impliquant un contrôle poussé des nanoobjets introduits. Les synthèses des AuNPs organiques sont développées à partir de la méthode de Brust, avec le 4-hydroxythiophénol et le 4-méthylthiophénol. Elles conduisent à des nanoparticules hybrides stables d’environ 2 nm. Les fractions de purifications sont analysées par MET, UV-visible, RMN et ATG, caractérisant le cœur d’or, la couche de ligands et leurs interactions. Il apparaît que les AuNPs hybrides présentent un assemblage de thiols en monocouche ou en multicouche. Une nouvelle voie de synthèse directe en phase aqueuse d’AuNPs d’environ 4 nm, stabilisées par le 4-hydroxythiophénol, est ensuite développée. Ces AuNPs sont purifiées par dialyse et caractérisées par MET, UV-visible, RMN et ATG. Les fractions d’AuNPs organiques, présentant différents états de surface, sont imprégnées dans la silice mésoporeuse SBA-15. Les isothermes d’adsorption et la manométrie sous diazote indiquent une bonne dispersion des AuNPs et une insertion dans les canaux. Nous introduisons l’exploration d’applications ciblées. L’utilisation des AuNPs organiques lors de l'oxydation d’alcènes tend à améliorer la sélectivité du sel de manganèse catalytique. Pour le domaine biomédical, les AuNPs aqueuses présentent une bonne dispersibilité en milieux aqueux biocompatibles. Les premiers tests in-vitro sur des cellules de sarcomes humains montrent une faible cytotoxicité et une bonne pénétration intracellulaire. / This Ph.D. work developed the controlled synthesis and purification of hybrid gold nanoparticles AuNPs, stabilized by organic thiols that are tuning their surface properties. The targeted applications are the catalysis and in the biomedical field, requiring a thorough control of the introduced nanoobjects. Syntheses of the organic AuNPs were developed from the Brust method, using 4-hydroxymercaptophenol or 4-methylmercaptophenol, leading to stable hybrid gold nanoparticles of size 2 nm. Purified fractions were characterized using TEM, UV-visible, NMR and TG analysis, issuing key data about the gold core, the organic layer and their interactions. Among the different fractions of AuNPs, the organic thiol ligands appeared to be assembled either as a monolayer or a multilayer pattern. A new direct route for synthesis of aqueous AuNPs of size 4 nm, stabilized by 4-hydroxymercaptophenol, has been developed. The AuNPs were purified using dialysis and characterized by TEM, UV-visible, NMR and TG analysis. Organic AuNPs, exhibiting different surface properties, were impregnated into SBA-15 mesoporous silica. Adsorption isotherms and nitrogen adsorption/desorption studies were in good agreement with the homogeneous distribution of AuNPs and the significant incorporation into the porosity. Finally, exploration of the targeted applications was started. The use of organic AuNPs for alkene oxidation tends to improve the selectivity of manganese salt catalyst. In the biomedical field, the aqueous AuNPs exhibited good dispersibility into biocompatible aqueous solvents. First in-vitro assays involving human sarcoma cells line showed limited cytotoxicity and good cellular uptake.

Today, nanotechnology has added a new dimension to materials technology by creating opportunities to significantly enhance the properties of existing conventional materials. Polymer nanocomposites belong to one such class of materials and even though they show tremendous promise for dielectric/electrical insulation applications (“nanodielectrics” being the buzzword), the understanding related to these systems is very premature. Considering the desired research needs with respect to some of the dielectric properties of polymer nanocomposites, this study attempts to generate an understanding on some of the existing issues through a systematic and detailed experimental investigation coupled with a critical analysis of the data. An epoxy based nanocomposite system is chosen for this study along with four different choices of nano-fillers, viz. TiO2, Al2O3, ZnO and SiO2. The focus of this study is on the properties of nanocomposites at low filler loadings in the range of 0.1 - 5% by weight and the properties under investigation are the permittivity/tan delta behaviors, DC volume resistivity, AC dielectric strength and electrical discharge resistant characteristics. Significant efforts have also been directed towards addressing the interface interaction phenomena in epoxy nanocomposites and their subsequent influence on the dielectric properties of the material. The accurate characterization of the dielectric properties for polymer nanocomposites depends on the dispersion of nanoparticles in the polymer matrix and to achieve a good dispersion of nanoparticles in the epoxy matrix for the present study, a systematic design of experiments (DOE) is carried out involving two different processing methods. Consequently, a laboratory based epoxy nanocomposite processing methodology is proposed in this thesis and this process is found to be successful in dispersing nanoparticles effectively in the epoxy matrix, especially at filler concentrations lower than 5% by weight. Nanocomposite samples for the study are prepared using this method and a rigorous conditioning is performed before the dielectric measurements. The dielectric properties of epoxy nanocomposites obtained in the present study show interesting and intriguing characteristics when compared to those of unfilled epoxy and microcomposite systems and few of the results are unique and advantageous. In an unexpected observation, the addition of nanoparticles to epoxy is found to reduce the value of nanocomposite real permittivity below that of unfilled epoxy over a wide range of frequencies. Similarly, it has been observed that irrespective of the filler type, tan delta values in the case of nanocomposites are either same or lower than the value of unfilled epoxy up to a filler loading of 5% by weight, depending on the frequency and filler concentration. In fact, the nanocomposite real permittivities and tan delta values are also observed to be lower as compared to the corresponding microcomposites of the same constituent materials at the same filler loading. In another significant result, enhancements in the electrical discharge resistant characteristics of epoxy nanocomposites (with SiO2/Al2O3 nanoparticles) are observed when compared to unfilled epoxy, especially at longer durations of discharge exposures. Contrary to these encouragements observed for few of the dielectric properties, the trends of DC volume resistivity and AC dielectric breakdown strength characteristics in epoxy nanocomposites are found to be different. Irrespective of the type of filler in the epoxy matrix, it has been observed that the values of both AC dielectric strengths and DC volume resistivities are lower than that of unfilled epoxy for the filler loadings investigated. The results mentioned above seem to suggest that there has to be an interaction between the nanoparticles and the epoxy chains in the nanocomposite and therefore, glass transition temperature (Tg) measurements are performed to characterize the interaction phenomena, if any. The results of Tg for all the investigated nanocomposites also show interesting trends and they are observed to be lower than that of unfilled epoxy up to certain nanoparticle loadings. This lowering of the Tg in epoxy nanocomposites was not observed in the case of unfilled and microcomposite systems thereby strongly confirming the fact that there exists an interaction between the epoxy chains and nanoparticles in the nanocomposite. Considering the variations obtained for the nanocomposite real permittivity and Tg with respect to filler loading, a dual nanolayer interface model is utilized to explain the interaction dynamics and according to the model, interactions between epoxy chains and nanoparticles lead to the formation of two epoxy nanolayers around the nanoparticle. Analysis shows that the characteristics of the interface region have a strong influence on the dielectric behaviors of the nanocomposites and the suggested interface model seems to fit the characteristics obtained for the different dielectric/electrical insulation properties rather well. Further investigations are performed to understand the nature of interaction between nanoparticles and epoxy chains through FTIR studies and results show that there is probably an occurrence of hydrogen bonding between the epoxide groups of the epoxy resin and the free hydroxyl (OH) groups present on the nanoparticle surfaces. The results obtained for the dielectric properties of epoxy nanocomposites in this study have widened the scope of applications of these functional materials in the electrical sector. The occurrence of lower values of real permittivity for nanocomposites is definitely unique and unexpected and this result has huge potential in electronic component packaging applications. Further, the advantages related to tan delta and electrical discharge resistance for these materials carry lot of significance since, electrical insulating materials with enhanced electrical aging properties can be designed using nanocomposite technology. Although the characteristics of AC dielectric strengths and DC volume resistivities are not found to be strictly advantageous for epoxy nanocomposites at the investigated filler loadings, these properties can be optimized when designing insulation systems for practical applications. In spite of all these advantages, serious and systematic research efforts are still desired before these materials can be successfully utilized in electrical equipment.

Polyethylene Terephthalate (PET) is one of the most important polymers in use today for packaging due to its outstanding properties. The usage of PET has grown at the highest rate compared with other plastic packaging over the last 20 years, and it is anticipated that the increase in global demand will be around 6% in the 2010-2015 period. The rheological behaviour, thermal properties, tensile modulus, permeability properties and degradation phenomena of PET/clay nanocomposites have been investigated in this project. An overall, important finding is that incorporation of nanoclays in PET gives rise to improvements in several key process and product parameters together - processability/ reduced process energy, thermal properties, barrier properties and stiffness. The PET pellets have been compounded with carefully selected nanoclays (Somasif MAE, Somasif MTE and Cloisite 25A) via twin screw extrusion to produce PET/clay nanocomposites at various weight fractions of nanoclay (1, 3, 5, 20 wt.%). The nanoclays vary in the aspect ratio of the platelets, surfactant and/or gallery spacing so different effect are to be expected. The materials were carefully prepared prior to processing in terms of sufficient drying and re-crystallisation of the amorphous pellets as well as the use of dual motor feeders for feeding the materials to the extruder. The rheological properties of PET melts have been found to be enhanced by decreasing the viscosity of the PET i.e. increasing the 'flowability' of the PET melt during the injection or/and extrusion processes. The apparent shear viscosity of PETNCs is show to be significantly lower than un-filled PET at high shear rates. The viscosity exhibits shear thinning behaviour which can be explained by two mechanisms which can occur simultaneously. The first mechanism proposed is that some polymer has entangled and few oriented molecular chain at rest and when applying high shear rates, the level of entanglements is reduced and the molecular chains tend to orient with the flow direction. The other mechanism is that the nanoparticles align with the flow direction at high shear rates. At low shear rate, the magnitudes of the shear viscosity are dependent on the nanoclay concentrations and processing shear rate. Increasing nanoclay concentration leads to increases in shear viscosity. The viscosity was observed to deviate from Newtonian behaviour and exhibited shear thinning at a 3 wt.% concentration. It is possible that the formation of aggregates of clay is responsible for an increase in shear viscosity. Reducing the shear viscosity has positive benefits for downstream manufacturers by reducing power consumption. It was observed that all ii three nanoclays used in this project act as nucleation agents for crystallisation by increasing the crystallisation temperature from the melt and decreasing the crystallisation temperature from the solid and increasing the crystallisation rate, while retaining the melt temperature and glass transition temperatures without significant change. This enhancement in the thermal properties leads to a decrease in the required cycle time for manufacturing processes thus potentially reducing operational costs and increasing production output. It was observed that the nanoclay significantly enhanced the barrier properties of the PET film by up to 50% this potentially allows new PET packaging applications for longer shelf lives or high gas pressures. PET final products require high stiffness whether for carbonated soft drinks or rough handling during distribution. The PET/Somasif nanocomposites exhibit an increase in the tensile modulus of PET nanocomposite films by up to 125% which can be attributed to many reasons including the good dispersion of these clays within the PET matrix as shown by TEM images as well as the good compatibility between the PET chains and the Somasif clays. The tensile test results for the PET/clay nanocomposites micro-moulded samples shows that the injection speed is crucial factor affecting the mechanical properties of polymer injection moulded products.

L’objectif de ce travail est de générer in situ des particules de dioxyde de titane dans une matrice polypropylène fondu au cours du procédé d’extrusion. La synthèse est basée sur des réactions d’hydrolyse-condensations d’un alkoxyde de titane (le n-tétrabutoxyde de titane). Une approche en milieu modèle a tout d’abord été développée offrant l’avantage de pouvoir travailler en milieu liquide sans prendre en compte de la viscosité du PP ni des effets de cisaillement. En se basant sur les données cinétiques déterminées en milieu modèle, la génération de ces particules de dioxyde titane a été ensuite transposée et modélisée dans le milieu polymère de masse molaire plus élevée. Les analyses chimique, structurale et morphologique ont permis de mettre au point l’élaboration in situ de nanocomposites PP/TiO2 présentant unestructure fractale avec des propriétés viscoélastiques particulières. Enfin l’étude des propriétés bactérienne de ce nanocomposite a mis en avant son pouvoir bactéricide (6Log) pour un taux de charge de 9 % massique. / Polypropylene/Titanium dioxide (PP/TiO2) nanocomposites were prepared from an original method based on the hydrolysis-condensation reactions of titanium alkoxide inorganic precursor premixed with PP under molten conditions. The synthesis is based on sol-gel method without solvent through extrusion process. A second treatment in hot water was applied in order to improve final conversion degree. First, hydrolysis-condensation reactions of titanium n-butoxide precursor were studied in model medium. Based on a kinetic equation carried out in the model medium, then the synthesis of titanium dioxide particles was transposed and modelled in polypropylene medium with high molar mass. Chemical, structural and morphological analyses highlight the in situ synthesis of bactericides PP/TiO2 nanocomposites andpresenting a particular morphological and rheological behaviour.

Les matériaux nanocomposites poreux organisés présentent de nombreuses propriétés dans le domaine de l’adsorption. Cette étude est portée sur la synthèse de matériaux poreux de grande aire spécifique fonctionnalisés par des nanoparticules métalliques en visant des applications dans le domaine de l’adsorption: en phase liquide et en phase gazeuse.La première application concerne la détection en phase liquide de molécules à de faibles concentrations. Des nanocomposites composés d’une matrice poreuse de silice dans laquelle sont insérées des nanoparticules de métaux nobles (i.e. Ag@SiO2 et Au@SiO2) sont étudiés comme substrats SERS en couplant thermodynamique et spectroscopie Raman. Ce couplage de l’étude de la réponse Raman et de l’étude thermodynamique de l’adsorption a conduit à une meilleure compréhension de l’influence des particules sur le seuil de détection de la molécule. L’influence de plusieurs paramètres sur la réponse Raman de la molécule sonde et sur ses propriétés d’adsorption a aussi été étudiée (la taille des particules, la nature chimique du métal, etc.).La seconde application concerne le stockage d’hydrogène. Des nanocomposites composés de matrices poreuses de silice ou de carbone dans lesquelles sont incorporées des nanoparticules d’un métal de transition (i.e. Ni@SiO2 et Ni@Carbone) sont étudiés comme matériaux de stockage en couplant manométrie et microcalorimétrie d’adsorption. La mise en place d’une méthode de réduction adaptée a constitué une étape importante de ce travail. Ce couplage d’études thermodynamiques de l’adsorption a permis de déterminer les propriétés d’adsorption de l’hydrogène à basse température et basses pressions de ces matériaux. / Nanocomposite organized porous materials present many properties in particular in the field of adsorption. This study was based on the synthesis of porous materials of high specific surface area functionalized with metal nanoparticles focusing in particular on two applications in the field of adsorption: one in the liquid phase and the other one in the gas phase.The first application is the detection of molecules in the liquid phase at low concentrations. Nanocomposites composed of a porous silica matrix in which are inserted noble metal nanoparticles (i.e. Ag@SiO2 and Au@SiO2) are studied as SERS (Surface Enhanced Raman Scattering) substrates by coupling thermodynamics and Raman spectroscopy. The coupling of the Raman response study and the thermodynamics of adsorption study leads to a better understanding of the influence of the particles on the molecule detection threshold. The influence of various parameters on the Raman response of the probe molecule and its adsorption properties were also studied (the particle size, the chemical nature of the metal, etc.)The second application relates to the storage of hydrogen since Nanocomposites composed of porous silica or carbon matrices in which are incorporated transition metal nanoparticles (i.e. Ni@SiO2 and Ni@Carbon) were studied as storage materials by coupling the adsorption manometry and microcalorimetry. The establishment of a suitable reduction method was an important step in this work. This coupling of thermodynamic studies of the adsorption was used to determine the adsorption properties of hydrogen at low temperature and low pressures of these materials.

Ces travaux décrivent l'élaboration de latex hybrides de polymère / nanotubes d'Imogolite et polymère / nanofeuillets d'hydroxydes doubles lamellaires (HDL) en milieu aqueux dispersé. Les deux charges inorganiques ont été choisies pour leurs propriétés thermiques, mécaniques et pour leur anisotropie de forme, ce qui pourrait permettre l'élaboration de films nanostructurés. Les latex ont été synthétisés par une stratégie originale basée sur le procédé de polymérisation RAFT en émulsion. Cette stratégie consiste à utiliser des copolymères hydrophiles (macroRAFT), comportant à la fois des unités d'acide acrylique et un groupe trithiocarbonate terminal, comme agents de couplage et stabilisants. Dans un premier temps, ces macroRAFTs ont été adsorbés à la surface des nanoparticules inorganiques, puis l'extension de ces chaînes a été réalisée par la polymérisation d'un monomère hydrophobe selon un procédé semi-batch. Des nanotubes d'Imogolite décorés de particules de latex ou des nanotubes d'Imogolite encapsulés ont été obtenus, selon les conditions de synthèse adoptées. L'effet de différents paramètres sur la morphologie finale des particules hybrides a été étudié. La nature de l'agent macroRAFT s'est avérée être un paramètre clé pour le succès de l'encapsulation. La même stratégie a été utilisée en vue de l'encapsulation des HDL. Quelles que soient les conditions investiguées, des latex stables contenant des particules d'HDL encapsulées par du polymère ont été formés. Dans tous les cas, la morphologie des latex nanocomposites a été caractérisée par MET et cryo-MET et reliée à la méthode de modification de la surface et aux conditions de polymérisation. Enfin, les propriétés mécaniques ainsi que la microstructure des films hybrides de polymère / nanotubes d'Imogolite ont été étudiées par DMA et MET, respectivement, et reliées à la morphologie des particules de latex / This work describes the elaboration of hybrid latexes of polymer / Imogolite nanotubes and polymer / layered double hydroxyde (LDH) nanosheets in aqueous dispersed media. The two inorganic materials were chosen as fillers for their thermal and mechanical properties and especially for their shape anisotropy, which could lead to the formation of nanostructured films. The latexes were synthesized through an original polymerization strategy based on the RAFT process in emulsion. The strategy consists in the use of hydrophilic random copolymers, containing acrylic acid units and a thiocarbonylthio end group, as both coupling agents and stabilizers. These copolymers, herein named macroRAFT agents, were tethered to the surface of the inorganic nanoparticles and chain extended by the polymerization of a hydrophobic monomer in a semi-batch process. Polymer-decorated Imogolite nanotubes or encapsulated nanotube bundles were obtained according to the process conditions. The effect of different parameters on the final morphology and latex stability was studied, and the macroRAFT nature was proven to be the key factor to achieve encapsulation. The same strategy was then applied to LDH materials. The different conditions tested all led to the encapsulation of the nanosheets. In both cases, the morphology of the nanocomposite latexes was characterized by TEM and cryo-TEM and correlated with the surface modification and the experimental conditions. The mechanical properties and the microstructure of hybrid films of polymer / Imogolite were studied by DMA and TEM, respectively, and correlated with the latex particles morphology

The ability to convert photons into mechanical motion is of significant importance for many energy conversion and reconfigurable technologies. Establishing an optical-mechanical interface has been attempted since 1881; nevertheless, only few materials exist that can convert photons of different wavelengths into mechanical motion that is large enough for practical import. Recently, various nanomaterials including nanoparticles, nanowires, carbon nanotubes, and graphene have been used as photo-thermal agents in different polymer systems and triggered using near infrared (NIR) light for photo-thermal actuation. In general, most photomechanical actuators based on sp bonded carbon namely nanotube and graphene are triggered mainly using near infra-red light and they do not exhibit wavelength selectivity. Layered transition metal dichalcogenides (TMDs) provide intriguing opportunities to develop low cost, light and wavelength tunable stimuli responsive systems that are not possible with their conventional macroscopic counterparts. Compared to graphene, which is just a layer of carbon atoms and has no bandgap, TMDs are stacks of triple layers with transition metal layer between two chalcogen layers and they also possess an intrinsic bandgap. While the atoms within the layers are chemically bonded using covalent bonds, the triple layers can be mechanically/chemically exfoliated due to weak van der Waals bonding between the layers. Due to the large optical absorption in these materials, they are already being exploited for photocatalytic, photoluminescence, photo-transistors, and solar cell applications. The large breaking strength together with large band gap and strong light- matter interaction in these materials have resulted in plethora of investigation on electronic, optical and magnetic properties of such layered ultra-thin semiconductors. This dissertation will go in depth in the synthesis, characterization, development, and application of two- dimensional (2D) nanomaterials, with an emphasis on TMDs and molybdenum disulfide (MoS2), when used as photo-thermal agents in photoactuation technologies. It will present a new class of photo-thermal actuators based on TMDs and hyperelastic elastomers with large opto-mechanical energy conversion, and investigate the layer-dependent optoelectronics and light-matter interaction in these nanomaterials and nanocomposites. Different attributes of semiconductive nanoparticles will be studied through different applications, and the possibility of globally/locally engineering the bandgap of such nanomaterials, along with its consequent effect on optomechanical properties of photo thermal actuators will be investigated. Using liquid phase exfoliation in deionized water, inks based on 2D- materials will be developed, and inkjet printing of 2D materials will be utilized as an efficient method for fast fabrication of functional devices based on nanomaterials, such as paper-graphene-based photo actuators. The scalability, simplicity, biocompatibility, and fast fabrication characteristics of the inkjet printing of 2D materials along with its applicability to a variety of substrates such as plastics and papers can potentially be implemented to fabricate high-performance devices with countless applications in soft robotics, wearable technologies, flexible electronics and optoelectronics, bio- sensing, photovoltaics, artificial skins/muscles, transparent displays and photo-detectors.