Rozprawy doktorskie na temat „Colloïde nanocomposite”

Les colloïdes nanocomposites organiques/inorganiques suscitent une attention considérable en raison de leur large gamme d'applications potentielles. L'auto-assemblage induit par la polymérisation (PISA) de copolymères à blocs en surface de nanoparticules inorganiques est reconnu comme une stratégie particulièrement efficace pour la synthèse de ces matériaux. Cette étude vise à synthétiser des brosses de polymères hydrophiles à la surface de particules de silice en utilisant la polymérisation radicalaire contrôlée par la voie nitroxyde (NMP) et à les utiliser par la suite comme macroamorceurs pour la croissance d'un second bloc hydrophobe. Des colloïdes hybrides avec des morphologies bien définies sont ainsi obtenus grâce à l'auto-assemblage des copolymères à blocs greffés et de leurs analogues non greffés. La première partie de ce travail est dédiée au greffage de brosses de polyélectrolytes faibles, le poly(acide méthacrylique-co-styrène) (P(AMA-co-S)), à partir de la surface de particules de silice. Des alcoxyamines ont été liées de manière covalente à des particules de silice de tailles variées en deux étapes, et avec une large gamme de densités de greffage. Ces particules de silice modifiées ont ensuite été utilisées comme amorceurs « supportés » pour la NMP de l’acide méthacrylique (AMA) en présence d’une faible quantité de styrène. En faisant varier systématiquement les conditions expérimentales, des particules de silice fonctionnalisées par des brosses de P(AMA-co-S) présentant différentes densités de greffage et différentes masses molaires, ont été obtenues. Leur comportement en solution aqueuse en fonction du pH et de la présence de sel ajouté a ensuite été étudié. Les particules de silice fonctionnalisées par les chaînes de P(AMA-co-S) ont été ensuite utilisées pour amorcer la copolymérisation en émulsion du méthacrylate de méthyle (MMA) et du styrène en présence de macroamorceur non greffé. Les expériences de contrôle effectuées en l’absence de silice ont conduit à la formation de particules de latex sphériques auto-stabilisées par le procédé PISA. L’influence de la concentration en macroamorceur, de sa masse molaire, du taux de solide et de la température sur la cinétique de polymérisation et la taille des particules de latex a été étudié en détails. Lorsque les particules de silice greffées ont été utilisées, l'auto-assemblage des copolymères à blocs amphiphiles à leur surface a conduit à la formation de particules hybrides de type framboise, cœur-coquille ou multicœur, en fonction de la taille des particules de silice, de la concentration en sel, ainsi que de la densité de greffage ou de la masse molaire du macroamorceur utilisé. La troisième partie de ce travail est consacrée à la synthèse par NMP de nano-objets à base de copolymères à blocs de type P(AMA-co-S)-b-P(MABz-co-S) stabilisés stériquement, par polymérisation en dispersion du méthacrylate de benzyle (MABz) en milieu alcoolique. La polymérisation réalisée à 85°C dans l'éthanol absolu est bien contrôlée, et conduit à la formation de particules sphériques, ainsi qu’à des morphologies supérieures telles que des batônnets, des fibres ou des vésicules selon la masse molaire du macroamorceur, de sa concentration et de la teneur en monomère. En présence des particules de silice fonctionnalisées, des morphologies hybrides originales composées de fibres courtes ou de vésicules liées à la surface de la silice ont été obtenues à nouveau par co-assemblage entre les chaînes de copolymères à bloc greffées et les chaînes non greffées. Ainsi, en faisant varier les conditions expérimentales et la nature chimique du monomère hydrophobe, une large gamme de morphologies hybrides a été obtenue à partir des mêmes particules de silice modifiées par des brosses de PAMA
Organic/inorganic nanocomposite colloids are attracting considerable attention due to their diverse range of potential applications. Polymerization-induced self-assembly of block copolymers on the surface of inorganic nanoparticles is recognized as a particularly effective strategy for the synthesis of these materials. This study aims to synthesize hydrophilic polymer brushes on silica particles using nitroxide-mediated radical polymerization (NMP) and subsequently employ them as macroinitiators for the growth of a second hydrophobic block. Hybrid colloids with well-defined morphologies are thus obtained through the co-assembly of surface-grafted and “free” ungrafted block copolymers. The first part of this work explores the grafting of weak polyelectrolyte brushes, namely poly(methacrylic acid-co-styrene) (P(MAA-co-S)), from the surface of silica particles. Alkoxyamine initiators were covalently attached to silica particles of varying sizes in two-steps, resulting in a large range of alkoxyamine grafting densities. These modified silica particles were subsequently employed as initiators for the NMP of MAA in the presence of a small amount of styrene as a controlling comonomer. By systematically varying the experimental conditions, silica particles functionalized with P(MAA-co-S) brushes, with tunable grafting densities and molar masses, were synthesized, and their pH- and salt-responsive behaviors were investigated. The resulting P(MAA-co-S)-functionalized silica particles were then employed in the aqueous emulsion copolymerization of methyl methacrylate (MMA) and styrene in the presence of free macroinitiator. Control experiments conducted without silica produced electrosterically stabilized spherical latex particles via polymerization-induced self-assembly. The effects of macroinitiator concentration, molar mass, solids content, and temperature on the polymerization kinetics and latex particles size were systematically studied. When PMAA-grafted silica particles were used, the co-assembly of the amphiphilic block copolymers on the silica surface and in solution, resulted in hybrid particles with raspberry, core-shell, or multicore morphologies depending on silica particle size, salt concentration, and the grafting density and molecular weight of the macroinitiator. The third part of this work reports the synthesis of sterically stabilized P(MAA-co-S)-b-P(BzMA-co-S) block copolymers nano-objects through alcoholic NMP dispersion polymerization of benzyl methacrylate (BzMA). The polymerization was well-controlled at 85°C in pure ethanol, producing copolymers that not only formed spherical particles but also self-assembled into more complex structures, such as worms and vesicles depending on the molar mass or concentration of the macroinitiator, and monomer content. Upon introducing P(MAA-co-S)-functionalized silica particles into the dispersion polymerization system, co-assembly of grafted and free block copolymers resulted in original hybrid morphologies composed of surface-tethered short worms or vesicles. By modifying the reaction conditions and monomer types, a wide range of nanocomposite colloidal morphologies were achieved using the same polymer brush-modified silica particles

Underfill material is a special colloidal dispersion system with silicon dioxide particles in the organic liquid. It is used to improve the reliability of integrated circuits (IC) packaging in the microelectronics. In order to successfully synthesize the nanocomposite underfill meeting the requirements of the chip package, it is necessary to have a fundamental understanding about the particle stability in the non-aqueous liquid and the relationship between materials properties and interphase structure in the composite. The results of this thesis contribute to the knowledge of colloidal dispersion of nanoparticles in organic liquid by systematically investigating the effects of particle size, particle surface chemistry and surface tension, and liquid medium polarity upon the rheological and thermal mechanical properties of underfill materials. The relaxation and dielectric properties studies indicate that the polymer molecular chain motion and polarization in the interphase region can strongly influence the material properties of nanocomposite, and so a good interaction between particle and polymer matrix is key. With this study, a potential nanocomposite underfill can be synthesized with low viscosity, low thermal expansion, and high glass transition temperature. The excellent transmittance of nanoparticles leads to further investigation of their ability as reinforcing filler in the photo-curable polymer.

Parmi les applications des colloïdes polymères aqueux, le domaine des revêtements est prédominant. Dans cette spécialité, la compréhension des propriétés mécaniques, en particulier tribologiques, est essentielle. La problématique générale de cette thèse s’inscrit dans l’amélioration de la compréhension du comportement tribologique de films issus de latex soumis au frottement d’une bille d’acier. Deux types de systèmes de latex acryliques bien distincts se dégagent de cette thèse. D’une part des systèmes modèles, où nous avons fait varier certaines grandeurs physico-chimiques pertinentes, susceptibles d’influencer la morpholgie particulière des films (composition, pH, quantité de tensioactif post-ajoutée) et d’autre part, des systèmes nanocomposites où une hétérogénéité de structure a été introduite (argile ou oxyde de cérium). Des essais ont été réalisés sur couches minces à l’aide d’un tribomètre équipé d’une caméra permettant de visualiser in-situ la géométrie du contact du frotteur sphérique sur les films de latex transparents. Il a été montré que la transition vitreuse est clairement visible par un pic de frottement après obtention de courbes maîtresses. La position de ce pic de dissipation a été comparée au pic de facteur de perte, obtenues via des essais volumiques, ce qui amène à de discuter de la pertinence de longueur caractéristique de vitesse de déformation en frottement. D’un point de vue physico-chimique, la formation et la structuration des films peuvent être directement corrélées aux propriétés tribologiques. Des effets de composition, pH, migration de tensioactifs et de microstructuration ont été mis en évidence
Among the applications of colloidal aqueous polymers, coatings are predominant. In this specialty, an understanding of mechanical properties, especially tribological, is essential. The general problematic of this thesis is to improve the understanding of the tribological behavior of films from latex subjected to the friction of a steel bead. Two types of distinct acrylic latex systems emerge from this thesis. Firstly, model systems, where we varied some relevant physical-chemical parameters that may influence particular latex film morphology (composition, pH, amount of surfactant post-added) and on the other hand, nanocomposites systems where a structure heterogeneity was introduced (clay or cerium oxide). Tests were performed on thin film using a tribometer equipped with a camera to visualize the in situ geometry of the contact area on the transparent latex films. It was shown that the glass transition is clearly visible by a friction peak after obtaining master curves. The position of this peak of dissipation was compared to the peak of loss factor, obtained through dynamic mechanical thermal analysis, which leads to discuss the relevance of the characteristic length of strain rate in friction. From a physico-chemical point of view, latex synthesis, post-synthesis parameter and structure of films can be directly correlated to tribological properties

Dans la première partie, nous présentons l'étude de la structure de nanocomposites nanosilice-latex et de colloïdes (micelles adsorbées, complexes de colloïdes), par diffusion de neutrons aux petits angles. Dans la deuxième partie, les propriétés mécaniques des nanocomposites sont discutées. Nous présentons également une simulation numérique d'un réseau de polymères très enchevetré. Dans le dernier chapitre, nous décrivant un prototype de spectromètre de diffusion de neutrons aux très petits angles, installé au Laboratoire Léon Brillouin.

Le développement de procédé évoluant à la pression atmosphérique représente un enjeu majeur dans le dépôt de couches minces nanocomposites. Parmi ces procédés, les Décharges à Barrières Diélectriques présentent l'avantage d'être un procédé vert sans effluent gazeux, pouvant facilement être intégrées dans une chaine de production industrielle. L'approche choisie pour la réalisation de couches minces nanocomposites repose sur l'injection sous forme d'aérosol d'une suspension colloïdale dans la DBD. Les nanoparticules semi-conductrices de TiO2 sont choisies et mise en suspension dans un alcool polymérisable tel que l'isopropanol. L’objectif de ce travail est de contrôler le transport des nanoparticules et la croissance de la matrice dans la DBD en vue de réaliser une couche mince nanocomposite.Différentes méthodes de formation de l'aérosol et de filtration sont évaluées, ainsi que différents gaz vecteur (Ar, N2). Dans tous les cas considérés, la décharge est filamentaire.L'estimation des valeurs des différentes forces s'exerçant sur une nanoparticule dans une DBD confortée par un modèle numérique à permis d'orienter les expérimentations. Il est ainsi possible, à partir des paramètres permettant de générer le plasma, d'influencer le dépôt des nanoparticules et la croissance de la matrice. Les dépôts obtenus sont analysés ex situ par microscopie électronique à balayage, spectroscopie infrarouge, Raman et à rayon X et in situ avec la diffusion laser.Dans le régime filamentaire considéré, nous montrons que le flux de gaz et la fréquence de la tension joue des rôles prépondérants sur le dépôt des couches minces nanocomposites. Cette étude a permis de mettre en évidence qu’une simple fréquence n’est pas suffisante pour déposer la couche mince nanocomposite. Cependant l’utilisation d’une double fréquence semble être la meilleure approche pour séparer le transport des nanoparticules de celui de la croissance de la matrice
Development of an atmospheric pressure process presents a major concern in the deposition of nanocomposites thin films. Among these processes, Dielectrics Barrier Discharges takes advantages to be green processes without gas effluent, which can be easily integrate in an industrial line production. The chosen approach for the nanocomposite thin film deposition is based on the injection of an aerosol of a colloidal suspension in the DBD. Semi-conductive TiO2 nanoparticles are chosen and put in suspension in a polymerizable alcohol as isopropanol. The objective of the present work is to control the transport of the nanoparticles as well as the matrix growth in the DBD in order to realize the nanocomposites thin film Different methods of the aerosol formation and filtration are evaluated, as well as the carrier gas (Ar, N2). In each case considered, the discharge works in filamentary. Estimating values of the different forces acting on the nanoparticles in a DBD comforted by a numerical model allowed to guide the experimentations. Thanks to the parameter which generated the plasma, it is possible to influence the nanoparticles deposition and the matrix growth. Depositions are ex situ analyzed by scanning electron microscopy, Infra-red, Raman, and X-ray spectroscopy and in situ by laser scattering. In the filamentary regime considered, we show that the gas flow rate and the frequency of the voltage play a dominant role on the deposition of nanocomposites thin films. This study allowed to highlight that a simple frequency is not enough to deposit the nanocomposite thin film. However, the use of a double frequencies seems to be the best way to separate the nanoparticles transport to the surface from that of the matrix growth

The search for cellulosic based products as a viable alternative for petroleum-based products was the impetus for covalently crosslinking lignocellulosic fibers and nanocellulose whiskers with poly(methyl vinyl ether) co maleic acid (PMVEMA) - polyethylene glycol (PEG). The lignocellulosics used were ECF bleached softwood (pine) and ECF bleached birch kraft pulp. This thesis also tests the hypothesis that water absorption and retention can be improved by grafting PMVEMA-PEG to the surface of ECF bleached kraft pulp hardwood and softwood fibers via microwave initiated crosslinking. The crosslinking of the PMVEMA to hardwood and softwood kraft ECF bleached pulp fibers resulted in enhanced water absorbing pulp fibers where the PMVEMA is grafted onto the surface of the fibers. The crosslinking was initiated both thermally and via microwave irradiation and the water absorption and water retention was measured as the percent of grafted PMVEMA. This was the first application of microwave crosslinking of pulp fibers with the goal of creating water absorbing pulp fibers. Ultimately, the water absorption values ranged from 28.70 g water per g dry crosslinked pulp fiber (g/g) to 230.10 g/g and the water retention values ranged from 26% to 71% of the water retained that was absorbed by the crosslinked pulp fibers. The microwave initiated crosslinked fibers had comparable results to the thermally crosslinked fibers with a decreased reaction time, from 6.50 min (thermal) to 1 min 45 sec (microwave). Cellulose nanowhiskers, crystalline rods of cellulose, have been investigated due to their unique properties, such as nanoscale dimensions, low density, high surface area, mechanical strength, and surface morphology and available surface chemistry. Prior to this study, the crosslinking of cellulose whiskers with the matrix via solution casting of liquid suspensions of whiskers and matrix had not been explored. The hypothesis to be investigated was that incorporating cellulosic whiskers with the PMVEMA-PEG matrix and crosslinking the whiskers with the matrix would yield films that demonstrate unique properties when compared to prior work of crosslinking of PMVEMA-PEG to macroscopic ECF bleached kraft pulp fibers. Solution cast composites of cellulose nanowhiskers-PMVEMA-PEG were crosslinked at 135 °C for 6.5 min and analyzed for crosslinking, thermal stability, strength and mechanical properties, whisker dispersion, and water absorption and uptake rates. The whisker-composites demonstrated unique properties upon crosslinking the whiskers with PMVEMA-PEG, especially the elongation at break and tensile strength upon conditioning of the final materials at various relative humidities. In addition, the whiskers improved the thermal stability of the PMVEMA-PEG matrix. This is significant as methods of improving processing thermal stability are key to developing new materials that utilize cellulose whiskers, PMVEMA, and PEG. This thesis addresses the hypothesis that cellulose nanowhiskers that are crosslinked with a matrix can create new whisker-matrix composites that behave differently after crosslinking.

Phosphorus-containing high performance polymers have been extensively studied during the last 10 years. These materials are of interest for a variety of optical and fire resistant properties, as well as for their ability to complex with the inorganic salts. This dissertation has focused on the nature of the phosphonyl group interactions with hydroxyl containing polymers, such as the poly(hydroxy ether)s. These may be considered linear models of epoxy resins and are also closely related to dimethacrylate (vinyl ester) matrix resins that are important for composite systems. It has been shown that bisphenol A poly(arylene ether phosphine oxide/sulfone) homo- or statistical copolymers are miscible with a bisphenol A-epichlorohydrin based poly(hydroxy ethers) (PHE), as shown by dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC), infrared spectroscopy and , solid state cross polarization-magic angle spinning nuclear magnetic resonance (CP-MAS). These measurements illustrate the strong hydrogen bonding between the phosphonyl groups of the copolymers and the pendent hydroxyl groups of the PHE as the miscibility inducing mechanism. Complete miscibility at all blend compositions was achieved with as little as 20 mole% of phosphine oxide units in the poly(arylene ether) copolymer. Replacement of the bisphenol A moiety by other diphenols, such as hydroquinone, hexafluorobisphenol A and biphenol did not significantly affect blend miscibilities. Miscible polymer blends with PHE were also made by blending poly(arylene thioether phosphine oxide), and fully cyclized phosphine oxide containing polyimides based on (prepared from 2,2'-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BPADA) and bis(m-aminophenyl) methyl phosphine oxide (DAMPO)) or bis(m-aminophenyl) phenyl phosphine oxide). Additional research has focused on the influence of these materials on the property characteristics of vinyl ester matrix resins and has shown that the concentration of phosphonyl groups controls the homogeneity of both oligomers and the resulting networks. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and fracture toughness measurements further confirmed the qualitative observations. Metal salts, such as CoCl2 and CuCl2 had earlier been demonstrated to form complexes/nanocomposites with phosphorus-containing poly(arylene ethers). It has been possible to prepare transparent films with 100 mol% of metal chlorides, based upon the phosphonyl groups. The films are transparent, unlike the opaque polysulfone control systems. FTIR results suggested the formation of inorganic salt and polymer complexes at low concentrations. TEM showed homogeneous morphology at low concentrations and excellent dispersion even at high mole % of salts. Cobalt materials reinforce the basic poly(arylene ether)s to provide higher modulus values and influence positively the char yield generated after TGA experiments in air. The cobalt salt/BPADA-DAMPO polyimide composites also yield transparent films, implying very small dimensions. Silica-polymer nanocomposites were also produced by mixing commercial silica colloid/N,N-dimethylacetamide (DMAc) fine dispersions (~ 12 nm) with bisphenol A poly(arylene ether phenyl phosphine oxide). The dry films produced by solution casting are transparent and silica colloids are evenly dispersed (~ 12 nm) into the polymer matrix as shown by TEM. These nanocomposites increased char yield compared with the polymer control, suggesting their fire retardant character. In comparison, the silica/polysulfone hybrid films prepared by the same methods were opaque and the char yield was not improved. This different phase behavior has been explained to be due to the hydrogen bonding between phosphonyl groups and silanol hydroxyl groups on the surface of the nanosilica.
Ph. D.

Ce travail de thèse porte sur le développement de nouvelles couches minces nanocomposites par plasma froid à la pression atmosphérique. L'objectif principal est d'améliorer la compréhension des mécanismes physico-chimiques régissant ce procédé de synthèse. La stratégie adoptée est basée sur l'injection via un aérosol d'une suspension colloïdale de nanoparticules d'oxyde métallique dans une décharge à barrière diélectrique opérant en atmosphère d'azote (décharge de Townsend). Dans un premier temps, la synthèse est réalisée de manière séquentielle, la fabrication d'une matrice inorganique de silice (SiO2) étant séparée du dépôt des nanoparticules (TiO2). Ensuite, les couches nanocomposites sont obtenues par un procédé en une seule étape à travers l'injection simultanée dans la décharge des nanoparticules et d'un précurseur polymérisable organosiliciée (HMDSO). Les travaux présentés dans ce manuscrit se divisent en quatre grandes parties : tout d'abord le procédé de fabrication des nanoparticules est présenté, et une étude de leur dispersion dans divers solvants chimiques est réalisée. Puis la deuxième partie s'intéresse à l'étape de nébulisation de la suspension colloïdale, à l'analyse des distributions de taille des objets injectés et à l'étude de leur transport sans plasma. En particulier, une étude de l'influence des principales forces agissant sur leur transport est réalisée. Ces résultats permettent ensuite d'évaluer l'impact de la décharge sur le transport, et sur la réalisation des couches minces nanocomposites. Finalement, l'analyse des propriétés obtenues pour ces couches minces sur des substrats de bois est présentée dans une dernière partie
This PhD work is focused on the development of a new generation of nanocomposite thin films using cold plasma at atmospheric pressure. The main objective is to improve the understanding of the mechanisms involved in this process.The strategy is based on the injection of a metal oxide nanoparticles suspension in a dielectric barrier discharge operating in nitrogen (Townsend discharge). At first, the nanocomposite thin film is deposited sequentially: the fabrication of the inorganic matrix of silica (SiO2) is separated from the collection of the nanoparticles (TiO2). Then, the nanocomposite layers are obtained by a one-step process using a direct injection inside the discharge of nanoparticles dispersed in a polymerizable organosilicon precursor (HMDSO). This manuscript is divided into four major parts: first, the synthesis of the nanoparticles and the study of their dispersion in different solvents are presented. Then, in the second part we focus on the atomization of the colloidal suspension, on the analysis of the size distributions of the injected objects and on the study of their transport towards the discharge area. These results are then used to assess the influence of the discharge on the transport and the quality of deposited nanocomposite thin films. Finally, the thin films properties are investigated when depositing on wood substrates

Colloidal particles dispersed in complex fluids such as hydrogels and polymer melts are important because nano-scale inclusions often impart unexpected and commercially attractive changes in the dispersed phase. Future development of these colloidal composites, and diagnostics to characterize their microstructure, demand a sound understanding of micro-scale dynamics. Accordingly, this thesis addresses (i) the steady and dynamic electric-field-induced displacements of spherical colloidal particles embedded in hydrogels, and (ii) the anomalous viscosity reduction of polymer-nanocomposite melts. The first problem is undertaken by solving a multi-phase electrokinetic model that quantifies how the viscoelasticity, compressibility, and hydrodynamic permeability of the hydrogel skeleton, and physicochemical properties of the inclusions, modulate the particle dynamics and electroacoustic responses. For the second problem, a hydrodynamic model is developed, and its analytical solution and numerical extension are adopted to interpret recent experiments in the literature where the bulk viscosity decreases anomalously with increasing particle volume fraction.
Les particules colloïdales dispersées dans les fluides complexes comme les hydrogels et des fontes de polymères sont importantes parce que les inclusions à nano-échelle répandent souvent des changements inattendus et commercialement intéressants dans la phase dispersée. Les développements futurs de ces composites colloïdales et des diagnostiques pour caractériser leur microstructure, demande une bonne compréhension de la dynamique à micro-échelle. En conséquence, cette thèse porte sure (i) la progression régulière et dynamique des déplacements de particules colloïdales sphériques embarqués dans des hydrogels induits par le champ électrique, et (ii) la réduction anormale de la viscosité des fontes en polymères nanocomposites. Le premier problème est entrepris par la résolution d'un modèle électrocinétique à multiple phases qui quantifie de façon où la viscoélasticité, de compression, la perméabilité hydrodynamiques de squelette d'hydrogel et des propriétés physico-chimiques des inclusions, et de moduler la dynamique des particules et réponses électroacoustiques. Pour le deuxième problème, un modèle hydrodynamique est développé, sa solution analytique et son extension numérique sont adoptées pour interpréter les expériences récentes en littérature où la plus grande viscosité diminue anormalement avec l'augmentation du volume fraction des particules.

Les assemblages colloïdaux représentent une nouvelle piste très prometteuse dans le domaine de l'ingénierie tissulaire. Idéalement, ce type d'assemblage permet l'obtention de matériaux injectables et gélifiants sur le site lésionnel, favorisant par la suite le développement de néo-tissus viables. Ce travail porte sur la formation de tels assemblages à base de chitosane et de poly(acide lactique) (PLA). Deux types d'assemblages ont été conçus et étudiés dans ce travail. Dans une première approche, le mélange de particules anioniques de poly (acide lactique) (PLA) avec du chitosane en solution faiblement acide conduit à la formation de « gels composites », résultant des interactions colloïde-polymère. Des analyses rhéologiques et de diffusion des rayons X aux petits angles ont permit de mettre en évidence le mode de formation et l'influence de plusieurs paramètres sur les propriétés finales de ces gels. Notamment, ils présentent des propriétés rhéofluidifiantes et un caractère réversible, c'est-à-dire que le gel peut se reformer après déstructuration mécanique. Le second type d'assemblage résulte du mélange de particules anioniques de PLA et de nanogels cationiques de chitosane, conduisant à la formation de « gels colloïdaux », par interactions colloïde-colloïde. L'influence de plusieurs facteurs sur la formation et les propriétés de ces gels a également été étudiée par mesures rhéologiques. Notre étude s'est notamment orientée sur la caractérisation et la stabilité des hydrogels physiques de chitosane sous forme colloïdale, ainsi que sur l'optimisation de leur cohésion
Colloidal assemblies may be a promising pathway to obtain injectable scaffolds favoring the development of neo-tissue in regenerative medicine. This work investigates the formation of such assemblies composed of chitosan, soluble or in suspension (nano-hydrogel), and poly(lactic acid) (PLA) nanoparticles. Two types of assemblies are studied. As a first approach, mixing negatively charged PLA particles and chitosan solution leads to the formation of “composite gels”, based on colloidpolymer interactions. Rheological and Small Angle X-Ray Scattering measurements highlighted the formation process and the influence of various parameters on final properties of these gels, which features shear-thinning and reversibility behavior, that is, the capacity to gel again after yielding. PLA nanoparticles could also be mixed with cationic chitosan nanoparticles, which are crosslinker free nano-hydrogels, leading to the formation of “colloidal gels”, based on colloid-colloid interactions. Influence of various parameters on gel synthesis and properties are investigated through rheological measurements. The study also focuses on the characterization and control of the morphological and cohesion properties of chitosan nanogel

博士
國防大學中正理工學院
國防科學研究所
96
Dispersion degree strongly influences the rheological properties of nanoparticles containing suspension and, as a consequence, the quality of the deposited film. Furthermore, their applications will be rigorously restricted if the bad dispersion can not be solved effectively. Therefore, knowing the dispersion degree of pastes before its application is inevitable. In this study, the dispersion of nanoparticles utilizing the physical and/or the chemical method within several suspension systems were investigated. The great emphasis is put on the effect of dispersion on the rheological properties of suspension. Both particle size measurement and morphology were usually carried out to analyze the effect of dispersion. However, these kinds of analysis are time-consuming, and their results might only display parts of the whole picture. The dispersed quality is very difficult to judge with only one single instrument. The studies on the rheological characteristics which offer the real on-time and intact processing data provide us a reliable way to analyze the dispersion degree of particles. The results show After SiO2 powders are treated with a silane coupling agent, leading to an improvement of the compatibility between particles and medium on one hand; That mixing with a three roll mill is an effective tool to break the agglomerates of silver nanoparticles in solvent, resulting in a better dispersion. In addition, the film deposited from suspension with Ag nanoparticles mixed by three roller mill has the lowest resistivity of approximately 3.64×102 μΩcm; The dispersion of Catalyst show that the catalyst can be dispersed more effectively by mixing with planet mixer than that by homogenizer based on our dispersal conditions. As an anionic surfactant SA is used as a dispersant, the adsorbed SA layer on the catalyst surfaces provides an electrostatic stabilization effect, resulting in a better dispersion degree. In addition, the effect of Disper Anion H14N(SA) on the activity of catalyst is insignificant. It is worth to be mentioned that some works are dedicated to investigate the rheological behaviors of the shear thickening fluid (STF). The shear thickening fluid has been reported that it can be applied in the defensive and the protective equipments. Utilization of this shear thickening characteristic, the ballistic protection capability afforded by fabricated, flexible body liquid armor can be enhanced tremendously. Not merely have military value, it can be further used to make the anti-impact materials to protect the human body, and, thus, increase the social welfare.

For more than a decade nanomaterials have attained huge attraction owing to the exceptionally different and excellent characteristics as compared to their bulk form. In the present research, we focus on understanding the properties and performance of nanocomposites in solid and liquid states. There are three major areas involved in this thesis research. Firstly, we will identify effective methods or techniques to evaluate nanomaterials. Conventional and non-conventional techniques will be implied. The second part is to study the interfacial reactions between nanoparticles (NPs) and fluid molecules. This is to obtain basic understanding of nanoparticles and their interactions with matrix materials. Thirdly, we will investigate the mechanical properties of nanocomposites. Experimental results showed that the mechanical properties of nanocomposites measured at macroscale exhibited differences when the shape and size of gold NPs were changed. The morphological characteristics of the material were shown effectively at the nanoscale based on the NPs' shape and size. The properties of NPs influenced the properties of gold colloid. Such changes were the result of the interfacial interaction of gold NPs and the host material.

碩士
國立高雄師範大學
化學系
96
A novel organic/inorganic nanocomposite with highly transparent, heat resistance and mechanical properties was prepared by sol-gel process. In this experiment, the organic matrix was synthesized by the condensation reaction of waterborne polyurethane (WPU), acrylate monomer (SR-444) and coupling agent (SAPSH). Then this complex was hydrolysis in acid solution at 70~75 ℃ to form a silanol derivative which could successfully bond with inorganic anti-static reagent (colloid Al2O3). Finally, the WPU/SR-444/SAPSH/Al2O3 organic/inorganic nanocomposite was crosslinked and synthesized by chain polymerization. TAIC , which contains three active vinyl groups, was used as a crosslinking agent to improve the thermal and mechanical characters of these nanocomposites. The new composites would be excellent optical materials used in photoelectric industry. The result showed that the surface resistance of WPU/SR-444 /SAPSH/colloid Al2O3 organic/inorganic nanocomposites had decreased. Besides, when 0~15wt% of colloid Al2O3 was used , the surface resistance of hybrid films reduced from 2.65×1011 to 2.05×109Ω/cm2 and it also achieved the anti-static character. Moreover, according to the best synthesis component of this nanocomposite, the Td value was 427.55 ℃ which was higher 14.66 ℃and34.24 ℃ than that of pure acrylate (polymerized from SR-444) and pure WPU resins respectively. When we added TAIC crosslinking reagent to strengthen the network bonding of WPU/SR-444/SAPSH/Al2O3 nanocomposite, the Td value was even up to 446.67 ℃,which was higher 19.12 ℃ than that of nanocomposite with non-crosslinking reagent. The hardness of transparent hybrid films could be attained to 8H~9H. In addition, the glass transition temperature was not detected below 200 ℃ by DSC. The excellent optical transparency was achieved in the visible region and its optical transparent degree could reach over 85 %. Finally, the morphology of the optic thin films, which were estimated by TEM, was evenly distributed with inorganic colloidal particles and the average particle size of these composites was 20~30 nm.

Ce travail de thèse porte sur le développement de nouvelles couches minces nanocomposites par plasma froid à la pression atmosphérique. L’objectif principal est d’améliorer la compréhension des mécanismes physico-chimiques régissant ce procédé de synthèse. La stratégie adoptée est basée sur l’injection via un aérosol d’une suspension colloïdale de nanoparticules d’oxyde métallique dans une décharge à barrière diélectrique opérant en atmosphère d’azote (décharge de Townsend). Dans un premier temps, la synthèse est réalisée de manière séquentielle, la fabrication d’une matrice inorganique de silice (SiO2) étant séparée du dépôt des nanoparticules (TiO2). Ensuite, les couches nanocomposites sont obtenues par un procédé en une seule étape à travers l’injection simultanée dans la décharge des nanoparticules et d’un précurseur polymérisable organosiliciée (HMDSO). Les travaux présentés dans ce manuscrit se divisent en quatre grandes parties : tout d’abord le procédé de fabrication des nanoparticules est présenté, et une étude de leur dispersion dans divers solvants chimiques est réalisée. Puis la deuxième partie s’intéresse à l’étape de nébulisation de la suspension colloïdale, à l’analyse des distributions de taille des objets injectés et à l’étude de leur transport sans plasma. En particulier, une étude de l'influence des principales forces agissant sur leur transport est réalisée. Ces résultats permettent ensuite d’évaluer l’impact de la décharge sur le transport, et sur la réalisation des couches minces nanocomposites. Finalement, l’analyse des propriétés obtenues pour ces couches minces sur des substrats de bois est présentée dans une dernière partie.
This PhD work is focused on the development of a new generation of nanocomposite thin films using cold plasma at atmospheric pressure. The main objective is to improve the understanding of the mechanisms involved in this process. The strategy is based on the injection of a metal oxide nanoparticles suspension in a dielectric barrier discharge operating in nitrogen (Townsend discharge). At first, the nanocomposite thin film is deposited sequentially: the fabrication of the inorganic matrix of silica (SiO2) is separated from the collection of the nanoparticles (TiO2). Then, the nanocomposite layers are obtained by a one-step process using a direct injection inside the discharge of nanoparticles dispersed in a polymerizable organosilicon precursor (HMDSO). This manuscript is divided into four major parts: first, the synthesis of the nanoparticles and the study of their dispersion in different solvents are presented. Then, in the second part we focus on the atomization of the colloidal suspension, on the analysis of the size distributions of the injected objects and on the study of their transport towards the discharge area. These results are then used to assess the influence of the discharge on the transport and the quality of deposited nanocomposite thin films. Finally, the thin films properties are investigated when depositing on wood substrates.

This dissertation work addresses two important aspects of nanotechnology - stable dispersion and self-assembly of colloidal nanostructures. Three distinctly different types of nano-scaled materials have been studied: 0-dimensional ZnO quantum dots (QDs), 1-dimensional carbon nanotubes (CNTs), and 2-dimensional alpha-zirconium phosphate (ZrP) nanoplatelets. Specifically, highly crystalline ZrP layered compounds with differences in diameters have been synthesized and fully exfoliated into monolayer platelets with uniform thickness, followed by their self-assembly into liquid crystalline structures, i.e., nematic and smectic. A novel colloidal approach to debundle and disperse CNTs has been developed by utilizing nanoplatelets to gather and concentrate sonication energy onto nanotube bundles. In such a fashion, CNTs are fully exfoliated into individual tubes through physical means to preserve their exceptional physical properties. Moreover, monodisperse ZnO QDs with high purity have been synthesized through a simple colloidal approach. Exfoliated ZrP nanoplatelets are used to tune the dispersion of ligand-free ZnO QDs from micron-sized aggregates to an individual QD level depending on the ratio between nanoplatelets and QDs. Dynamic analysis suggests that the dispersion mechanism mainly involves the change of QD dispersion free energy due to the presence of nanoplatelets, so that QDs can interact favorably with the surrounding media. In addition, the nanoplatelet-assisted dispersion approach has been utilized to disperse QDs and CNTs into polymeric matrices. Dispersion - property relationship in polymer nanocomposites has been systematically investigated with emphasis on optical properties for QDs and mechanical properties for CNTs.

The thesis describes the study of slow dynamics of confined polymers and soft colloids. We study the finite size effect on the dynamics of glassy polymers using newly developed interfacial microrheology technique. Systematic measurement have been performed to address the issue of reduction of glass transition under confinements. Slow and heterogeneous dynamics are the underlined observed behavior for dynamics in confined glassy polymers. The slow relaxation dynamics and dynamical heterogeneity in polymer grafted nanoparticles (PGNPs) systems were studied using advanced X - ray photon correlation spectroscopy (XPCS) techniques. Our studies presented in this thesis on dynamics of polymer grafted nanoparticle systems in melts and solution are the first attempt to study them experimentally. Thus our work shed the light about new technique to study confined system more accurately and explore new soft colloidal system to study fascinating dynamics and interesting phase behavior. In Chapter 1, we provide the theoretical background along with brief review of the literature for understanding the results presented in this thesis. The details of the experimental set up and their operating principle along with the details of the experimental conditions are provided in Chapter 2. In Chapter 3 we present our newly developed technique (interfacial microrhelogy) and its consequences to study the complex fluids at interface. Chapter 4 discusses the concentration and temperature dependent glassy dynamics in confined glassy polymers. In Chapter 5 we provide the structural and dynamical study of polymer grafted nanoparticles in melts and solutions. We provide the summary of our result and the future prospective of the work in Chapter 6. Chapter-1 provides the ground work and theoretical aspects for understanding the results presented in this thesis. It starts with the discussion about the slow dynamics of complex fluids and transit to dynamic behavior of polymer in confinement, glassy dynamics in confinements . This also discusses the basic aspects of studying viscoelastic properties using rheology, interface rheology, microrheology, interface microrheology techinques. In continuation it discusses structure and dynamics of different soft colloids investigated for last decade and then theoretical aspects of XPCS is discussed. Towards the end of this Chapter, we discuss the procedure to explain and understand systems dynamical heterogeneity near glass like phase transition. Chapter-2 contains the details of the experimental techniques which has been used for the study of confined polymers and soft colloids. Brief introduction to basic principles of the measurements followed by details of the material and methods have been provided. Chapter-3 we discuss the interafacial microrheology of different complex fluids and advantages of the techniques is discussed in Chapter 3. This includes discussion about the technique sensitivity at the surface using quantum dots (QDs) as a probe and about the configuration of the QDs at/on monolayer. Later on establishment of the technique has been demonstrated through easurements on arachidic acid, poly(methylmethacrylate) (PMMA), poly(vinylacetate) (PVAc), poly(methylacrylate) (PMA) monolayers. The extracted subdiffusive nature of QDs in on monolayers through mean square displacement has been explained using fractional Brownian motion model. Towards the end of the chapter we discuss about the extraction of real and imaginary elastic modulus from mean square displacement data using generalized Stokes-Einstein relation for the quasi two dimensional systems and explains about the possible viscoelastic transition in the different monolayers. The concentration and temperature dependent glassy dynamics of confined polymers (PMMA) are discussed in Chapter-4. We demonstrate the microscopic nature of spatio-temporal variation of dynamics of glassy polymers confined to a monolayer of 2 􀀀 3 nm thickness as a function of surface density and temperature. It illustrates the systems dynamical heterogeneity and explain the observed large reduction of glass transition temperature in confined system through finite size effect. In Chapter 5 we discuss the result based on systematic studies of dynamics of PGNPs in melts and solutions. In addition it also illustrates the structural anisotropy and anomalous dynamical transitions in binary mixture of PGNPs and homopolymers in good solvent condition. It provides temperature and wave vector dependent XPCS measurements on polymer grafted nanoparticles with the variation of functionality. The functionality ( f ) dependent nonmonotonic relaxation in melts of PGNPs and solvent quality dependent non monotonic relaxation of PGNPs system have been elaborated in the continuation. We present possible phase behavior of PGNPs system in good solvent with addition of homopolymer of two different molecular weight. Chapter 6 contains the summary and the future perspective of the work presented.

The thesis describes the study of slow dynamics of confined polymers and soft colloids. We study the finite size effect on the dynamics of glassy polymers using newly developed interfacial microrheology technique. Systematic measurement have been performed to address the issue of reduction of glass transition under confinements. Slow and heterogeneous dynamics are the underlined observed behavior for dynamics in confined glassy polymers. The slow relaxation dynamics and dynamical heterogeneity in polymer grafted nanoparticles (PGNPs) systems were studied using advanced X - ray photon correlation spectroscopy (XPCS) techniques. Our studies presented in this thesis on dynamics of polymer grafted nanoparticle systems in melts and solution are the first attempt to study them experimentally. Thus our work shed the light about new technique to study confined system more accurately and explore new soft colloidal system to study fascinating dynamics and interesting phase behavior. In Chapter 1, we provide the theoretical background along with brief review of the literature for understanding the results presented in this thesis. The details of the experimental set up and their operating principle along with the details of the experimental conditions are provided in Chapter 2. In Chapter 3 we present our newly developed technique (interfacial microrhelogy) and its consequences to study the complex fluids at interface. Chapter 4 discusses the concentration and temperature dependent glassy dynamics in confined glassy polymers. In Chapter 5 we provide the structural and dynamical study of polymer grafted nanoparticles in melts and solutions. We provide the summary of our result and the future prospective of the work in Chapter 6. Chapter-1 provides the ground work and theoretical aspects for understanding the results presented in this thesis. It starts with the discussion about the slow dynamics of complex fluids and transit to dynamic behavior of polymer in confinement, glassy dynamics in confinements . This also discusses the basic aspects of studying viscoelastic properties using rheology, interface rheology, microrheology, interface microrheology techinques. In continuation it discusses structure and dynamics of different soft colloids investigated for last decade and then theoretical aspects of XPCS is discussed. Towards the end of this Chapter, we discuss the procedure to explain and understand systems dynamical heterogeneity near glass like phase transition. Chapter-2 contains the details of the experimental techniques which has been used for the study of confined polymers and soft colloids. Brief introduction to basic principles of the measurements followed by details of the material and methods have been provided. Chapter-3 we discuss the interafacial microrheology of different complex fluids and advantages of the techniques is discussed in Chapter 3. This includes discussion about the technique sensitivity at the surface using quantum dots (QDs) as a probe and about the configuration of the QDs at/on monolayer. Later on establishment of the technique has been demonstrated through easurements on arachidic acid, poly(methylmethacrylate) (PMMA), poly(vinylacetate) (PVAc), poly(methylacrylate) (PMA) monolayers. The extracted subdiffusive nature of QDs in on monolayers through mean square displacement has been explained using fractional Brownian motion model. Towards the end of the chapter we discuss about the extraction of real and imaginary elastic modulus from mean square displacement data using generalized Stokes-Einstein relation for the quasi two dimensional systems and explains about the possible viscoelastic transition in the different monolayers. The concentration and temperature dependent glassy dynamics of confined polymers (PMMA) are discussed in Chapter-4. We demonstrate the microscopic nature of spatio-temporal variation of dynamics of glassy polymers confined to a monolayer of 2 3 nm thickness as a function of surface density and temperature. It illustrates the systems dynamical heterogeneity and explain the observed large reduction of glass transition temperature in confined system through finite size effect. In Chapter 5 we discuss the result based on systematic studies of dynamics of PGNPs in melts and solutions. In addition it also illustrates the structural anisotropy and anomalous dynamical transitions in binary mixture of PGNPs and homopolymers in good solvent condition. It provides temperature and wave vector dependent XPCS measurements on polymer grafted nanoparticles with the variation of functionality. The functionality ( f ) dependent nonmonotonic relaxation in melts of PGNPs and solvent quality dependent non monotonic relaxation of PGNPs system have been elaborated in the continuation. We present possible phase behavior of PGNPs system in good solvent with addition of homopolymer of two different molecular weight. Chapter 6 contains the summary and the future perspective of the work presented.

Recent advancements in nanotechnology and emerging applications of nanomaterials in various fields have stimulated interest in fundamental scientific research dealing with the size and structure controlled synthesis of nanoparticles. The unique properties of nanoparticles are largely size dependent which could be tuned further by varying shape, structure, and surface properties, etc. The preparation of monodisperse nanoparticles is desirable for many applications due to better control over properties and higher performance compared to polydispersity nanoparticles. There are several methods for the synthesis of nanoparticles based on top-down and bottom-up approaches. The main disadvantage of top-down approach is the difficulty in achieving size control. Whereas, uniform nanoparticles with controllable size could be obtained by chemical methods but most of them are difficult to scale up. Moreover, a separate step of size separation is necessary in order to achieve monodispersed which may lead to material loss. In this context, a post-synthetic size modification process known as digestive ripening is highly significant. In this process, addition of a capping agent to poly disperse colloid renders it highly monodisperse either under ambient or thermal conditions. In addition to size control, digestive ripening is also effective in controlling the structure of nanoparticles in colloidal solution comprising two different elements. Use of co-digestive ripening strategy in conjunction with solvated metal atom dispersion (SMAD) method of synthesis resulted in hetero structures such as core–shell, alloy, and composite nanoparticles. Despite the versatility of digestive ripening process, the underlying mechanism in controlling size and structure of nanoparticles are not understood to date. The aim of this thesis is to gain mechanistic insight into size control of digestive ripening as well as to investigate structure control in various binary systems. Objectives  Study digestive ripening of Au nanoparticles using various alkyl amines to probe the mechanism  Study co-digestive ripening of binary colloids consisting of two metals, Pd and Cu prepared separately by SMAD method  Study co-digestive ripening of binary colloids consisting of a metal (Au) and a semiconductor (CdS) prepared separately by SMAD method  Study vaporization of bulk brass in SMAD reactor and analyse phase, structure, and morphology of various Cu/Zn bimetallic nanoparticles obtained from bulk brass under various experimental conditions Significant results In chapter 1, fundamental processes of nanoparticle formation and common synthetic techniques for the preparation of monodisperse nanoparticles are briefly discussed. Chapter 2 presents a mechanistic study of digestive ripening process with regard to size control using Au nanoparticles as a model system. Three long chain alkyl amine molecules having different chain length were used as digestive ripening agents. The course of digestive ripening process was analysed by UV-visible spectroscopy and transmission electron microscopy. The experimental conditions such as concentration of digestive ripening agent, time, and temperature were found to influence the size distribution of nanoparticles. The average particle size was found to be characteristic of metal-digestive ripening agent combination which is considered as the optimum size preferred during digestive ripening under a given set of experimental conditions. This study discusses stabilization of optimum sized particles, surface etching, and reversibility in digestive ripening. Chapter 3 describes the synthesis and characterization of PdCu alloy nanoparticles by co-digestive ripening method. Syntheses of individual Pd and Cu colloids were carried out by SMAD method. Pd nanoparticles obtained using THF as solvent and in the absence of any capping agent resulted in an extended small Pd nanowire network assembly. Morphological evolution of spherical Pd nanoparticles from Pd nanowire network structure was observed with the use of capping agent, hexadecyl amine (HDA) in SMAD method. Co-digestive ripening of Pd and Cu colloids was studied at various temperatures. This study revealed temperature dependent diffusion of Cu atoms into Pd lattice forming PdCu alloy nanoparticles. Next, co-digestive ripening of a colloidal system comprising a metal and a semiconductor was explored. Au-CdS combination was chosen for this study owing to its interesting photocatalytic properties. Chapter 4 deals with the synthesis of Au and CdS nanoparticles by SMAD method and Au/CdS nanocomposite by co-digestive ripening. CdS nanoparticles of size 4.0 + 1.2 nm and Au nanoparticles of size 5.6 + 1.1 nm were obtained as a result of digestive ripening process. Au/CdS nanocomposite obtained by co-digestive ripening was characterized by a matrix-like structure made up of CdS nanoparticles in which Au nanoparticles were embedded. CdS nanoparticles were found to establish an intimate surface contact with Au nanoparticles and the matrix of CdS surrounding Au was developed via aggregation during digestive ripening. Chapter 5 describes a comprehensive study on various Cu/Zn bimetallic nanoparticles obtained from bulk brass. Vaporization of bulk brass in SMAD reactor led to a deploying process and further growth of nanoparticles from phase separated Cu and Zn atoms formed a composite structure. The characterization of Cu/Zn nanocomposite revealed covering of composite surface with Cu resulting in a core-shell structure, Cu/Zn@Cu. Post-synthetic digestive ripening of these core-shell composite particles showed diffusion of Zn atoms to the composite surface in addition to size and shape modification. Annealing of Cu/Zn nanocomposites prepared in THF resulted in α-CuZn alloy nanoparticles via sequential transformation through η-CuZn5, γ-Cu5Zn8, and β-CuZn (observed as marten site) phases.

Recent advancements in nanotechnology and emerging applications of nanomaterials in various fields have stimulated interest in fundamental scientific research dealing with the size and structure controlled synthesis of nanoparticles. The unique properties of nanoparticles are largely size dependent which could be tuned further by varying shape, structure, and surface properties, etc. The preparation of monodisperse nanoparticles is desirable for many applications due to better control over properties and higher performance compared to polydispersity nanoparticles. There are several methods for the synthesis of nanoparticles based on top-down and bottom-up approaches. The main disadvantage of top-down approach is the difficulty in achieving size control. Whereas, uniform nanoparticles with controllable size could be obtained by chemical methods but most of them are difficult to scale up. Moreover, a separate step of size separation is necessary in order to achieve monodispersed which may lead to material loss. In this context, a post-synthetic size modification process known as digestive ripening is highly significant. In this process, addition of a capping agent to poly disperse colloid renders it highly monodisperse either under ambient or thermal conditions. In addition to size control, digestive ripening is also effective in controlling the structure of nanoparticles in colloidal solution comprising two different elements. Use of co-digestive ripening strategy in conjunction with solvated metal atom dispersion (SMAD) method of synthesis resulted in hetero structures such as core–shell, alloy, and composite nanoparticles. Despite the versatility of digestive ripening process, the underlying mechanism in controlling size and structure of nanoparticles are not understood to date. The aim of this thesis is to gain mechanistic insight into size control of digestive ripening as well as to investigate structure control in various binary systems. Objectives  Study digestive ripening of Au nanoparticles using various alkyl amines to probe the mechanism  Study co-digestive ripening of binary colloids consisting of two metals, Pd and Cu prepared separately by SMAD method  Study co-digestive ripening of binary colloids consisting of a metal (Au) and a semiconductor (CdS) prepared separately by SMAD method  Study vaporization of bulk brass in SMAD reactor and analyse phase, structure, and morphology of various Cu/Zn bimetallic nanoparticles obtained from bulk brass under various experimental conditions Significant results In chapter 1, fundamental processes of nanoparticle formation and common synthetic techniques for the preparation of monodisperse nanoparticles are briefly discussed. Chapter 2 presents a mechanistic study of digestive ripening process with regard to size control using Au nanoparticles as a model system. Three long chain alkyl amine molecules having different chain length were used as digestive ripening agents. The course of digestive ripening process was analysed by UV-visible spectroscopy and transmission electron microscopy. The experimental conditions such as concentration of digestive ripening agent, time, and temperature were found to influence the size distribution of nanoparticles. The average particle size was found to be characteristic of metal-digestive ripening agent combination which is considered as the optimum size preferred during digestive ripening under a given set of experimental conditions. This study discusses stabilization of optimum sized particles, surface etching, and reversibility in digestive ripening. Chapter 3 describes the synthesis and characterization of PdCu alloy nanoparticles by co-digestive ripening method. Syntheses of individual Pd and Cu colloids were carried out by SMAD method. Pd nanoparticles obtained using THF as solvent and in the absence of any capping agent resulted in an extended small Pd nanowire network assembly. Morphological evolution of spherical Pd nanoparticles from Pd nanowire network structure was observed with the use of capping agent, hexadecyl amine (HDA) in SMAD method. Co-digestive ripening of Pd and Cu colloids was studied at various temperatures. This study revealed temperature dependent diffusion of Cu atoms into Pd lattice forming PdCu alloy nanoparticles. Next, co-digestive ripening of a colloidal system comprising a metal and a semiconductor was explored. Au-CdS combination was chosen for this study owing to its interesting photocatalytic properties. Chapter 4 deals with the synthesis of Au and CdS nanoparticles by SMAD method and Au/CdS nanocomposite by co-digestive ripening. CdS nanoparticles of size 4.0 + 1.2 nm and Au nanoparticles of size 5.6 + 1.1 nm were obtained as a result of digestive ripening process. Au/CdS nanocomposite obtained by co-digestive ripening was characterized by a matrix-like structure made up of CdS nanoparticles in which Au nanoparticles were embedded. CdS nanoparticles were found to establish an intimate surface contact with Au nanoparticles and the matrix of CdS surrounding Au was developed via aggregation during digestive ripening. Chapter 5 describes a comprehensive study on various Cu/Zn bimetallic nanoparticles obtained from bulk brass. Vaporization of bulk brass in SMAD reactor led to a deploying process and further growth of nanoparticles from phase separated Cu and Zn atoms formed a composite structure. The characterization of Cu/Zn nanocomposite revealed covering of composite surface with Cu resulting in a core-shell structure, Cu/Zn@Cu. Post-synthetic digestive ripening of these core-shell composite particles showed diffusion of Zn atoms to the composite surface in addition to size and shape modification. Annealing of Cu/Zn nanocomposites prepared in THF resulted in α-CuZn alloy nanoparticles via sequential transformation through η-CuZn5, γ-Cu5Zn8, and β-CuZn (observed as marten site) phases.