Thèses sur le sujet « Non-aqueous synthesis »

Thin film composite (TFC) membranes have long been used by many large-scale applications (i.e., water and wastewater treatment). Recently, conventional polymeric TFC membranes are facing with short longevity due to high fouling tendency and susceptibility at extreme operational conditions. On the other hand, ceramic membranes are also suffering from disadvantages like low selectivity, unreliable control over porosity and pore size which makes it difficult to achieve a reproducible final product. The aim of this project was to develop a high selective TFC membranes incorporated by functionalized TiO2 nanoparticles for aqueous and nonaqueous media applications.In order to obtain high permeable aromatic polyamide thin film nanocomposite (TFN) nanofiltration membrane, the conventional interfacial polymerization (IP) reaction was applied as the embedding media for functionalized nanoparticles. For this purpose, TFN nanofiltration membrane with appropriate structural and separation properties was developed by dispersing the aminosilanized TiO2 nanoparticles inside the diamine monomer and polymerizing the monomer in the presence of these particles. Surface-modified ceramic substrate was used to obtain high mechanical resistant composite membrane. Results from spectrometry analyses represent that the silane coupling agent called AAPTS has been successfully grafted onto the external surface of TiO2 after the chemical modification. Upon incorporation of TiO2 nanoparticles, thermal stability of nanocomposite is significantly improved in comparison with TFC membrane. Morphological investigations prove that the functionalized TiO2 nanoparticles could effectively change the surface properties and roughness of NF membranes. Performance results show that ultra-low concentration (0.005 wt%) of amine functionalized TiO2 nanoparticles improves the salt rejection as well as water flux. Flux can be further improved by the incorporation of higher percentage of the modified TiO2 into polymer membrane.In order to obtain nanofiltration membrane with high permeability and antifouling properties, TFN membrane was synthesised by dip-coating of a hydrophilized porous poly(vinylidene fluoride) (PVDF) support in different poly(vinyl alcohol) (PVA) aqueous solution. In order to improve the interfacial adhesion of nanoparticles in PVA blend, an endothermic carboxylation reaction under acidic condition was carried out on the TiO2 surface using chloroacetic acid (ClCH2COOH). Glutaraldehyde (GA) was used as a cross-linker to bond resultant PVA chains and enhances the stability of the coated PVA layer, accordingly. TiO2 nanoparticles were dispersed in PVA solution in pure and functionalized forms. Scanning electron microscopy (SEM) identified various topographies by the incorporation of TiO2 nanoparticles. Performance results showed a 40% rejection improvement of divalent salt (MgSO4) by the incorporation of 1.0 wt% surface-carboxylated TiO2 nanoparticles into PVA solution. A simultaneous 57% retention improvement was achieved for uncharged solute (PEG 2000). After PVA coating with TiO2 incorporation, the flux recovery ratio of PVDF membrane was significantly improved from 45 to 94%.In order to apply TFN membranes in non-aqueous media, a range of thin film nanocomposite solvent resistant nanofiltration membranes (SRNF) were fabricated by interfacial polymerization technique. TiO2 nanoparticles were used as inorganic fillers into polyamide chain network. TiO2 nanoparticles’ surfaces were functionalized in order to improve their compatibilization inside the polyamide matrix. For this purpose, Monoethanolamine (MEOA) and triethylenetetramine (TETA) agents were applied to aminate TiO2 nanoparticles, while thionyl chloride (TCl) was used to chlorinateation. Morphological investigations identified various topographies formed by the incorporation of TiO2 nanoparticles with different chemistry. Transport properties of membranes were evaluated by two different dyes: positively-charged Crystal Violet (CV) (408 Da) and neutral Bromothymol Blue (BTB) (624 Da). Performance results reveal that high rejection was achieved by the TFN membrane fabricated by TCl-modified TiO2 with BTB and CV rejection of 90 and 93%, respectively. These satisfactory rejection data for both charged and uncharged dyes can be attributed to formation of a dense structure after exposing the chlorinated TiO2 nanoparticles into interfacial polymerization reaction on membrane surfaces.

A diblock copolymer of Poly (Styrene-b- [ethylene-co-propylene]) has been used as a stabilizer in non-aqueous dispersion polymerizations of methyl methacrylate and vinyl acetate in n-heptane. The particles thus produced were stabilized by well defined surface layers of ethylene-propylene copolymer chains. The dependence of the particle size on the stabilizer, monomer and initiator concentrations was studied. Both seeded and one-shot polymerization techniques were investigated. Polymer particles were characterized by transmission electron microscopy to determine particle shape and size. The long term stability of both types of polymer particles suggests that the anchoring efficiency in both systems was good. Rheological studies confirmed the sphericity of the particles and showed the particles to be non-flocculated under shear. The thickness of the surface layer was determined from viscosity studies of the dispersions at 298, 308 and 318K. Solution viscosities dispersions at of a narrow distribution standard of ethylene-propylene copolymer in n-heptane and in a binary liquid mixture of n-heptane and n-propanol (79:21, v/v) at 298, 308 and 318K were obtained in order to estimate the root-mean-square end-to-end distance of free ethylene-propylene copolymer chains. The thickness of the surface layer was observed to increase on raising the temperature and to decrease on changing the solvency of the dispersion medium from a good solvent to almost a theta solvent for the ethylene-propylene copolymer chains. The dimensions of the surface layer were slightly larger than the dimensions of the free ethylene-propylene copolymer chains in solution suggesting that long ethylene-propylene chains terminally anchored at the interface are only slightly extended over random coil dimensions. Calculations of the mean separation distance between adjacent stabilizing ethylene-propylene copolymer chains indicated close-packing of ethylene-propylene copolymer chains at the particle-liquid interface which may contribute to the slight extension of the ethylene-propylene copolymer chain conformation. The theta-conditions for ethylene-propylene copolymer in a mixture of n-heptane and n-propanol were determined using samples obtained by hydrogenating polyisoprene standards. The solvency of the dispersion medium for the stabilizing ethylene-propylene copolymer chain on the polymer particles was reduced until flocculation occurred, and this was achieved by cooling the dispersion system to find the critical flocculation temperature or by adding a non-solvent (n-propanol) for the ethylene-propylene copolymer chains at constant temperature to find the critical flocculation volume. The polymer dispersions just retained stability at theta conditions and started to lose stability when the dispersion medium was changed to slightly worse than a theta system for the ethylene-propylene chains. The close correspondence of the flocculation conditions to the theta conditions for free ethylene-propylene copolymer chains confirms that the steric stabilization mechanism is operative for these dispersions.

A general review on macrocyclic ligands with particular emphasis to dibenzocryptand 222 and dibenzo 18 crown 6 is given in the first part of the thesis (Chapter 1). This is followed by an exhaustive literature survey on the stability constants (hence free energies of complexing), enthalpies and entropies of metal cations with cryptands (dibenzocryptand 222, benzocryptand 222, cryptand 222) and crown ethers (dibenzo 18 crown 6, benzo 18 crown 6, 18 crown 6) in water and in non-aqueous solvents at 298.15 (Chapter 2). The experimental part (Chapter 3) also includes a detailed description of the principals involved in calorimetry as well as the methods used for the calculation of reaction enthalpies. Stability constant data for alkali-metal and silver cations with dibenzocryptand 222 in five dipolar aprotic solvents (N,N dimethyl-formamide, dimethylsulphoxide, acetonitrile, propylene carbonate and nitromethane) at 298.15 K are reported. These data are used to calculate the standard free energies of the complexation process involving metal(I) cations and dibenzocryptand 222 in the dipolar aprotic solvents. Free energy data are combined with enthalpy data obtained in this work in order to evaluate the entropies of complexation of these cations with dibenzocryptand 222 in these solvents. A linear correlation previously shown for metal(I) cations and cryptand 222 in DMF, Me2SO, AN, PC and NM between entropies of complexing and entropies of solvation of metal(I) cations in dipolar aprotic solvents is also found for dibenzocryptand 222. The results obtained in this thesis provide further evidence that the complexation process with metal (I) cations and cryptands is mainly controlled by the state of solvation of the cation in the solvent. Enthalpies of solution of dibenzocryptand 222 in the dipolar aprotic solvents are reported and the thermodynamic parameters for the extraction process in the water + nitromethane solvent system as described by M+(H2O) + 22B2B(NM) → M+22B2B (NM) are calculated (Chapter 4). Thermodynamic parameters of solution and transfer of dibenzo 18 crown 6 are discussed with respect to corresponding data for dibenzocryptand 222. The transfer free energies of metal ion dibenzocoronates from water to a number of solvents are calculated and it is shown that, unlike cryptates, there is an interaction between the complexed cation and the solvent in metal ion dibenzocoronates in dipolar aprotic media. Thermodynamic parameters of complexation for alkali-metal and dibenzo 18 crown 6 in acetonitrile are reported. The complexation process seems to be enthalpically and entropically controlled (Chapter 5). Synthesis of crown compounds and heats of solution of 18 crown 6 carried out at several temperatures as well as DeltaCp values in water are presented in Chapter 6.

Enantioselective synthesis is one of the most important challenges of today's synthetic chemists. In particular, the hydroxylation of non-activated C-H bonds remains a significant challenge that few chemical catalysts have succeeded to overcome. The P450 enzymes, a family of heme-containing monooxygenases including more than 5000 known isoforms, are gaining considerable attention due to their ability to catalyze the very difficult regio- and stereo-selective oxidation of inactivated C-H bonds. The use of such enzyme is however limited by their functional complexity, low activity, need for cofactors, and poor stability. In this thesis, we elected to study the human P450 CYP3A4, because of its high substrate promiscuity. The first part of the project involved the replacement of the required cofactors (NADPH and cytochrome P450 reductase) by some cheap hydrogen peroxide donors or organic peroxides. Several surrogates, such as sodium percarbonate and cumene hydroperoxide, were found to be efficient at replacing the natural cofactor, without a significant loss of stability and activity. The second part of this thesis deals with optimization of the lyophilization conditions. Among the numerous additives tested, some sugars led to significant lyoprotection during the freeze-drying process. Finally, in the third part, the effect of the presence of organic solvents and ionic liquids on CYP3A4 activity was evaluated.

Amidases are hydrolytic enzymes that catalyze the hydrolysis of amides to their corresponding carboxylic acids and ammonia. Amidases are ubiquitous in nature, and they have been isolated from a wide range of microorganisms, the most common source being bacteria. Amidases are recognized as potential industrial biocatalysts in processes that involve the synthesis of chiral compounds, mostly used in the pharmaceutical, agrochemical and food industries. The discovery of amidases from extremophiles has increased the potential for application of these enzymes for the development of new processes. In nonaqueous media, amidases have the ability to synthesize enantiopure amides due to the shift in thermodynamic equilibrium towards synthesis. For synthesis to occur, an acyl donor and an acyl acceptor are required, in which the acyl acceptor acts as a nucleophile. The applicability of amidases in non-aqueous media opens new possibilities for processes in which the enzyme can be used for the industrial synthesis of commercially relevant new products. A novel amidase was previously isOlated from a thermophilic Geobacillus species, and the amidase was cloned and expressed in an Escherichia coli BL21 strain. Also in previous studies, it was shown that the enzyme exhibits both amide hydrolysis and acyl transfer activities. The highest activity of the G. pallidus RAPc8 amidase was observed at 50°C in the presence of acetamide and substrate preference was towards aliphatic, short chain amides. Furthermore, the enzyme displayed enantioselectivity towards lactamide, which is a chiral compound. The amidase compound showed selectivity towards the D-isomer of lactamide and no detectable activity on the L-isomer. This study presents the investigation and development of a novel biocatalytic process that involves the synthesis of enantiopure amides in non-aqueous media, using the G. pal/idus RAPc8 amidase. The amidase was produced and expressed in E. coli BL21.

Colloidal polymeric particle dispersions have found many industrial applications, one of which is as the ‘ink’ particles within electrophoretic displays. Traditionally these displays have shown high resolution, increased battery life and excellent readability in sunlight, when compared with more commonly used displays, such as liquid crystal displays (LCDs). However, commercially available examples have only demonstrated black and white displays, or screens with coloured filters over the black and white particles, resulting in ‘washed out’ colours. The development of a full colour electrophoretic display holds great industrial potential to advance the field of electrophoretics, as well as available technology. A stabiliser is required during the synthesis of said particle dispersions, in order to control the parameters of the particles, as well as to ensure they remain stable and do not aggregate or settle out. Numerous different stabilisers have been successfully employed, although each has disadvantages and difficulties associated with it. This work describes the development of a block copolymer stabiliser of poly(methyl methacrylate) and poly(octadecyl acrylate). The stabiliser itself was synthesised using controlled radical polymerisation techniques, namely atom transfer radical polymerisation (ATRP). ATRP allowed for the molecular weight, composition and distribution of chain lengths to be tailored to meet certain requirements. The stabilisers were then employed in non-aqueous dispersion (NAD) polymerisations, to synthesise dispersions of monodisperse, cross-linked and dyed particles, with good size control and spherical packing. Initial dispersions showed desirable characteristics for electrophoretic fluids, but exhibited a thermoresponsive gelation once allowed to stand for a period of time. The nature of this gelation process was investigated, before modifications were made to the structure of the stabiliser. This new stabiliser was then used in NAD polymerisations, which resulted in particles which still possessed all the desirable properties previously observed, without the gelation. These particles were then tested successfully for their application in electrophoretic displays.

Great interest was recently devoted to the use of inorganic particles as a reinforcing filler in tires for the automotive industry. In fact,the reinforcing of elastomers by the addition of these fillers affects the stiffness, strength, elongation at break, fracture toughness, energy dissipation (rolling resistance), friction to ice or wet grip, wear (abrasion resistance)and on the material processability. Therefore, the technology improvement of tires currently has to satisfy the requirements of sustainable development in order to reduce fuel consumption, environmental pollution and acoustic noise. Carbon black has been the only additive used for this purpose for a long time but silica is now becoming the alternative reinforcing filler; as it offers a lot of advantages, such as better rolling resistance and reduction of the heat buildup; moreover, it can be suitably employed in all cases where the black color is not required. Natural rubber-silica (NR-SiO2) composites are usually prepared by mechanical mixing. Unfortunately, silica particles have a strong tendency to interact with each other within the elastomeric matrix, favoring the inhomogeneous dispersion due to particle tendency to agglomerate and in principle to reduce the filler-rubber interaction. Significant contributions to overcome the disadvantages derived from filler-filler interaction of the silica particles; they are obtainable by enhancing the filler-rubber interaction, which causes additional cross-linking in the rubber structure. The enhancement of filler-rubber interaction is obtained by the use of coupling agents which interact with both the polymer (hydrophobic) and the silica(hydrophilic) surface groups,due to the presence of different functionalities at the ends of the molecules. An alternative approach and object of the present Ph.D thesis,is to prepare composites by in situ formation of the silica filler particles by sol-gel hydrolysis and condensation of tetraethoxysilane(TEOS. Therefore,the aim of this work is to prepare silica-natural rubber (NR-SiO2) composites, with the intention of improving the properties which normally the compound, prepared by mechanical blending possesses. Several factors like nature of the solvent, nature of the catalyst, medium pH, molar ratio between alkoxysilane and water or solvent, gelling and drying temperatures are fundamental sol-gel parameters which can modify the process of the nanocomposite preparation in order to optimize the better homogeneity of the filler distribution inside the rubber matrix. Therefore, considering the filler particle growth in situ in the polymeric matrix, it is possible to distinguish two possible preparation techniques which differ in some of the factors affecting the sol-gel process: aqueous and non-aqueous in situ sol-gel methods. In addition to these factors that influence the preparation of the composite, the amount of the filler present in the silica-rubber composite affects the final performance. In fact, the enhancement in mechanical properties can be achieved when the composite contains the optimal amount of the filler required to form a continuous filler network within the rubber matrix; filler amounts less of this percolation threshold show mostly constant and poor mechanical properties. The presence of a continuous filler network and its homogeneity depends on the filler characteristics, such as size and shape of the particles and on the in situ composite preparation method used. The formation of a convenient filler network is in turn relatable to the physical and chemical interactions among the particles and among their aggregates (filler-filler interaction) and to the chemical and physical interactions between the particles and the matrix (filler-rubber interaction). The presence of functional groups on the particle surface can significantly influence the interface between the filler particles and the rubber matrix; consequently, modifying the filler-filler and filler-rubber interaction leads to the variation of the reinforcement level of the composites. With the intention to investigate and to rationalize the effects induced by surface functionalization of the filler on the properties of rubber composites, during the aqueous sol-gel synthesis of the silica the surface was functionalized by using trialkoxysilane having different functional groups. These functionalities were selected among those which are suitable for promoting the formation of differently shaped silica particles or for modulating the filler-filler and the filler-rubber interactions. Silica particles were modified by molecules containing alkylthiol, thiocarboxylate, alkyldisulfide, alkyltetrasulfide (silica functionalized with containing S groups); vinyl, propyl, octyl chains, alkylamine, alkylcyanate and alkylisocyanate groups (silica functionalized with containing N groups). For this purpose a mixture of TEOS and TMSPM ((3-mercaptopropy)trimethoxysilane) or TESPD (bis(3-triethoxysilylpropyl)disulfide) or TESPT (bis(3-triethoxysilylpropyl) tetrasulfide) or NXT (3-octanoylthio-1propyltriethoxy) or VTEOS (vinyltriethoxysilane) or PTEOS (triethoxy(propyl)silane) or OCTEOS (triethoxy(octyl)silane) or APTEOS ((3-aminopropyl)triethoxysilane) or CPTEOS (3-cyanopropyltriethoxysilane) or ICPTEOS (3-(triethoxysilyl)propylisocyanate) were introduced in NR latex (containing 60 % dry rubber, 39.3 % of water and 0.7% of NH3) during the aqueous sol-gel process. The functionalized molecules were selected with the aim of promoting the formation of different shapes on silica particles (anisotropic or spherical), moreover of modifying the filler-filler and filler-rubber interaction through the chemical functionalities of substituents. In the aqueous in situ sol-gel method, the presence of large amounts of water helps the silica precursors to react quickly in the early stage of the synthesis in rubber matrix, allowing thus to increase the hydroxyl group numbers on particle surfaces, making them less compatible with the rubber and in this way favoring particle aggregation. Through the non aqueous in situ sol gel method, the oxygen present in silica nanoparticles is provided by a suitable reaction and not, as in the aqueous in situ sol gel method, by the water solvent. During this method, the addition of two simple solvents on the metal oxide precursor can generate water in situ that can start sol-gel hydrolysis and condensation reactions. In order to work in an environment without the presence of the water as initial reactant, the silica-rubber composite by the non-aqueous in situ sol-gel method was prepared starting from a solution of dry NR with toluene (inert solvent) and TEOS, which was added to formic acid and alcohol (ethanol of benzylalcohol). Therefore, well defined amounts of water were formed through the esterification reaction produced by formic acid and alcohol, which control the formation of metal oxide growth within the rubber matrix. Moreover, in order to understand better the morphology of the silica particle growth in NR through the in situ sol-gel method, bare silica and functionalized silica powders were prepared by using the same method without the rubber. These powders were morphologically characterized with the intention of more easily evaluating the shape, the size, the surface area, the effect of the metal oxide precursor and the modification of the silica surface. Regarding the composites, the amount of silica was determined by thermogravimetric analysis(TGA) in air. The stability and the reactivity of the functional groups and the hydrolysis rate of the alkoxy groups of the trialkoxysilanes in the early stage of the sol-gel reaction were evaluated by ATR-FTIR. The homogeneity of the particle dispersion, the dimension and shape of silica aggregates were investigated by SEM and TEM, to draw appropriate relations between the filler morphology and the reinforcement of the elastomeric network. The efficacy of the filler network in reinforcing the rubber matrix was assessed by swelling measurements. The Electron Spin Resonance(ESR) behavior of nitroxide radical, introduced as spin probe in order to check the rigidity of the rubber chains, was also investigated. The static and dynamic-mechanical properties of the nanocomposites, both uncured and vulcanized, were investigated and discussed referring to the network morphology, allowing to suggest a connection between the silica precursors used and the functional properties and the amount of the filler. The vulcanization kinetics was also studied, as well as the homogeneity of the dispersion of the filler and the rubber networks. Hardness, abrasion resistance, tensile analysis and compression set results of vulcanized composites were discussed taking into account the structural, morphological and mechanical characteristics determined before. Silica-natural rubber composites for tire applications with a controlled composition and morphology was obtained by in situ sol-gel method and compared with conventional mechanical blending prepared by using silica Rhodia and dried NR. Regarding the in situ sol-gel method of nanocomposite preparation, two different synthetic approaches were carried out by starting from the same silica precursor: aqueous and non aqueous methods. Deep investigation on the relationship between composition, size and morphology of the silica particles, dispersion network degree and dynamic mechanical behavior of uncured composites allowed to rationalize the final performance of the cured composites. In fact, the efficacy of silica filler to improve the mechanical properties of the tires for the automotive industry is related both to the interaction among the silica particles and aggregates (filler-filler interaction) and to their capability to interact with the rubber matrix (filler-rubber interaction). Therefore, the characteristics of the silica such as shape, size, surface area, nature of the surface (OH group, functional molecules and amount), degree of aggregation lead to modify the nature of the interface with the rubber and also the homogenous distribution of the filler network. The obtained results for aqueous in situ sol-gel silica-natural rubber preparation led to the following conclusions: - The aqueous sol-gel method is a promising procedure to prepare nanocomposites from silica precursor TEOS mixed to trialkoxisilanes having different functional groups when the filler precursor doesn’t react quickly through hydrolysis and condensation reactions in water environment and allow to control the filler-filler and filler-rubber interactions. - The functional groups from different substituted silicon alkoxide precursors promote during the sol-gel process the formation of different silica particle shapes and modify the filler-filler and filler-rubber interaction.In particular,the precursor functionalities induced the formation of anisotropic shaped silica particles, unlike the spherical ones derived from TEOS. - Different precursors give rise to particle networks with different degrees of continuity, depending on physical and chemical properties of particles they originate. Spherical or slightly anisotropic particles with homogeneous size show the best self assembling behavior and form continuous networks. When particles contain surface groups able to interact with each other (e.g. hydroxyl, amino and thiol groups), the formation of chemical bonds makes the filler-filler interaction stronger along the network. - The network continuity within the composite is the main prerequisite to obtain strong rubber reinforcement. Not homogeneous distribution of the filler and irregular segregation of particles induce large voids in the network, lowering the dynamic-mechanical properties. However, it appears that a strong chemical interaction among particles can balance the absence of a fully continuous network, preserving high storage modulus. This is the case of the network in NR-TMSPM, where the thiol functionality assists the bonding interaction. On the contrary, the large voids observed in the network of NR-OCTEOS are not compensated by bonding interactions among particles, which are absent or very weak due to the presence of the surface alkyl groups. - The different filler-rubber interaction due to substituents able to chemically interact with the polymer, promotes the homogeneous distribution of the filler particles even if its contribution to the reinforcement properties is less effective than that to the filler-filler interaction. Thus filler-filler interaction governs the dynamic-mechanical properties of silica rubber composites either through the shape induced physical interactions responsible for the network formation, or by the chemical interaction among particle surface groups. - To sum up when a choice among different functionalized silica is required, the suggestion is to look for well assembled and continuous filler networks, eventually assisted by chemical interaction among particles. The second condition seems very important, in fact in the case of NXT network, the homogeneous particle distribution is not sufficient to guarantee strength; instead the dynamic-mechanic behavior of NR-NXT is enhanced after thermal treatment which allows the sulphur-rubber interaction. - Regarding the properties of the vulcanized composites, it is evident that the preparation of the silica in situ improve the rigidity, the hardness, the tensile strength and reduce the dissipation of the energy, which means an improvement in rolling resistance. The obtained results for non-aqueous in situ sol-gel silica-natural rubber preparation led the following conclusions: -The non-aqueous in situ sol-gel synthesis is a procedure to prepare nanocomposites allowing the in situ growth of small particles in rubber matrix in the absence of large amount of water. In addition, due to the slow hydrolysis and condensation reaction rate of the precursors it possible to control at molecular level the growth of the metal oxide particles and therefore the filler-filler interaction and the dispersion in rubber matrix. - Non-aqueous in situ sol-gel silica-natural rubber nanocomposites were prepared by in situ esterification reaction between formic acid and ethylalcohol or benzylalcohol which produce controlled amount of water for the hydrolysis and condensation reaction. Therefore inside the dried NR it is possible to growth high amount of silica particles well distributed in a network were the particles are less aggregated and show lower filler-filler interaction in comparison with the composite prepared by conventional blending route. - Silica-natural rubber composites were obtained containing large amount of well dispersed silica (75 phr or 43% wt) without using coupling agents. -The nature of the alcohol involved in the esterification reaction influences the shape and the size of the silica prepared in swollen natural rubber. Silica particles produced in ethanol environment are bigger than those produced in presence of benzylalcohol, and create an effective reinforcement of the rubber when their amount is higher than 60 phr (37% wt). In spite of the different particle dimensions, silica produced from the two different routes are equally highly dispersed in the rubber matrix, due to the lower hydrophilicity of the surface, and a large amount of filler is required to form an efficient silica network able to reinforce the composite. -This behavior, peculiar of silica particles prepared by non aqueous in situ method, confirm that even if a homogeneous distribution of the particles in the matrix is required to obtain an efficient and strong reinforcement of the rubber, highly separated particles with low filler-filler interaction hinder an efficient filler network. On the other side the non aqueous synthesis allows to load a large amount of silica in the rubber, which could not be loaded with the traditional blending method without using a compatibilizer or disperdent agent.

Ce travail concerne la synthèse et la caractérisation structurale de nanocristaux de faible taille (~1-3 nm) d’oxydes métalliques simples, à savoir le dioxyde de titane (TiO2), le dioxyde d’étain (SnO2) et le monoxyde de zinc (ZnO). Les synthèses ont été réalisées au moyen de méthodes sol-gel non-aqueuses voire strictement non-hydrolytiques sous contrôle cinétique. La caractérisation structurale s’est principalement appuyée sur la diffraction des rayons X, la microscopie électronique en transmission et la méthode des fonctions de distribution de paires atomiques, obtenues grâce à la diffusion totale des rayons X, couplées à des méthodes de modélisation à l’échelle atomique. Dans le cas de TiO2, des nanoparticules d’anatase bien cristallisées de 4 nm à 8 nm ont été synthétisées. Le ratio molaire de donneur d’oxygène par rapport au titane s’est avéré être un paramètre influençant fortement la taille des particules. Nous avons également mis en évidence la formation d’une phase intermédiaire caractérisée par des nanoparticules faiblement cristallisées de très faible taille dont la structure pourrait s’apparenter à une structure brookite désordonnée. Pour SnO2, des nanocristaux présentant une structure rutile ont été obtenus avec des tailles comprises entre 2 nm et 4 nm. Dans le cas de l’utilisation d’un éther, nous avons mis en évidence la formation concomitante d’une phase organique polymérisée et de nanoparticules primaires dont la structure intermédiaire présente de fortes similitudes avec la structure rutile. L’utilisation de solvants possédant une fonction benzyle en présence de tétrachlorure d’étain a conduit à la formation d’eau dans le système. Dans le cas de ZnO, nous avons montré que l’utilisation d’une base organique pour initier la formation du réseau oxyde dans une solution méthanolique d’acétate de zinc en présence d’un agent complexant du zinc permettait d’obtenir des nanoparticules de l’ordre de 1 nm. Même pour les faibles valeurs de taille, les nanoparticules présentent une structure très proche de la wurtzite avec un désordre croissant au niveau du réseau cationique
The aim of this work was to synthesize small size (~1-3 nm) metal oxide nanocrystals namely titanium dioxide (TiO2), tin dioxide (SnO2) and zinc oxide (ZnO), and to study their structure. Syntheses were conducted via non-aqueous or even strictly non-hydrolytic sol-gel methods under kinetic control. The structural characterization was mainly carried out by X-Ray diffraction methods, transmission electronic microscopy and the study of pair distribution functions, obtained by X Ray total scattering, coupled with atomic scale modelling methods. In the case of TiO2, anatase nanocrystals were obtained with sizes ranging between 4 nm and 8 nm. The molar ratio of the oxygen donor with respect to titanium was shown to be an important parameter to control the nanoparticle size. In peculiar conditions we have been able to isolate an intermediate phase characterized by very small sized and poorly crystallized nanoparticles which the structure can be assimilated to a disordered brookite structure. Concerning SnO2, rutile-type nanocrystals were synthesized with sizes ranging between 2 nm and 4 nm. The use of an ether as oxygen donor led to the simultaneous formation of an organic polymeric phase and of primary nanoparticles characterized by an intermediate structure close but still different from the rutile-type structure. Moreover, the use of benzyl-type solvents in the presence of tin tetrachloride led to the formation of water in the system. Lastly, for ZnO, we have shown that using an organic base to induce the formation of the metal oxide network in a methanolic solution of zinc acetate in the presence of a strong complexing agent of the zinc allowed us to obtain wurtzite nanocrystals of ultrasmall sizes around 1 nm. Even for the smallest sizes, the nanoparticles exhibit a structure very close to that of wurtzite with an increasing disorder of the cationic network

Amino-functionalized organic–inorganic hybrid materials with a narrow distributed nanostructure of 2–4 nm in size were obtained by means of a template-free and non-aqueous procedure. Simultaneous twin polymerization of novel amino group containing twin monomers with 2,2′-spirobi[4H-1,3,2-benzodioxasiline] has been applied for this purpose. The amino groups of the organic–inorganic hybrid material are useful for post derivatization
Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich

Les ferrofluides etudies sont constitues de particules de maghemite solubilisees en milieu aqueux (ferrofluides ioniques) ou non aqueux (ferrofluides surfactes). Le mode de synthese permet de controler les caracteristiques des grains (taille et densite superficielle de charge)

碩士
國立臺灣大學
環境工程學研究所
99
In recent years, suspended colloidal zero valent iron nanoparticles have been applied to the dechlorination of aqueous chlorinated solvents in polluted groundwater. However, due that nonaqueous chlorinated solvents and water are immiscible, nonaqueous chlorinated solvents could not react with aqueous colloidal zero valent iron nanoparticles. To overcome the drawback, eco-friendly dense nonaqueous suspensions of nano-scale zero-valent iron (DNAPNZVI) were developed. In this study, dimethyl carbonate (DMC) was chosen as the surface-modified nano zero valent iron’s carrying liquid. DMC has low toxicity, high biodegradability, immiscibility with water, denser density than water and low viscosity, which meets the criteria of the carrying liquid. Octadecyl phosphate, cetyltrimethylammonium bromide or poly methyl methacrylate was used to modify the surfaces of commercial nano zero valent iron (NZVI). The results of demonstrated that three kinds of DNAPNZVI were easily miscible with chlorinated solvent. In addition, NZVI modified with CTAB or PMMA, were stably suspended in DMC. The mean particle size ranged from 50 to 100 nm, surface area was 16.54 m2/g and the content of iron was 83-85 wt%. The results of dechlorination experiment for 262 mg/L TCE in DMC-saturated water showed that there was not TCE degradation found during ten hours with PMMA/Fe0. DNAPNZVI, at the concentration of 10 Fe g/L and with a specific gravity of 1.073 was injected into with grain size from 200 to 250 μm saturated quartz sand column. The result of experiment revealed that the capillary force of the oil-water system in saturated quartz sand column to be overcome was 1050 N/m2 by PMMA/Fe0 was 1050 N/m2 and 1788 N/m2 for CTAB/Fe0.

博士
國立清華大學
化學工程學系
94
The design of inorganic nano silica into polymer matrix to form a polymer-nanosilica hybrid has been proven to be an effective way to improve the thermal and mechanical properties of polymers. A non-aqueous synthetic method to prepare nanometer scale silica in both epoxy and polyamideimide resin has been established through direct thermal heating under catalyst in this study. In the first part of this study, a series of epoxy-bridged ethoxysilane precursors have been synthesized by reacting multifunctional aminoalkoxysilanes with diglycidyl ether of bisphenol-A (DGEBA) epoxy resin. The reactions between aminoethoxysilanes with DGEBA epoxy have been monitored and characterized by FTIR, 1H NMR, and 29Si NMR spectra in this study. Organometallic dibutyltindilaurate, and alkaline tetrabutylamonium hydroxide have been used as curing catalysts to investigate the thermal curing behaviors and cured properties of epoxy-bridged ethoxysilane precursors. The maximum exothermal curing temperatures of epoxy-bridged polyorganosiloxanes precursors are found to appear around the same region of 120℃ in DSC analysis. The addition of catalysts to the Epoxy/APTES precursor shows significant influence on the cured structure; however, the catalysts exhibit less influence on the cured structure of Epoxy-APMDS precursor and Epoxy/APDES precursor. Curing catalysts also show significant enhancement in increasing the thermal decomposition temperature (Td50s ) of cured network of trifunctional epoxy-bridged polyorganosiloxane (Epoxy/APTES). High Td50s of 518.8 and 613.6 in the cured hybrids of Epoxy/APTES and Epoxy/APMDS precursors are also observed, respectively. When trialkoxysilane terminated epoxy-bridged polyorganosiloxanes precursor are cured with catalyst, there is no obvious Tg transition found in the TMA analysis of cured network. The cured network of trialkoxysilane terminated epoxy-bridged polyorganosiloxanes also exhibits the lowest coefficient of thermal expansion (CTE) among the three kinds of alkoxysilane terminated epoxy-bridged polyorganosiloxanes. The organic-inorganic hybrid from epoxy-bridged polyorganosiloxanes after thermal curing process shows better thermal stability than the cured resin network of pure epoxy-diaminopropane. The effects of molecular structures and mobility on the thermal properties of epoxy-bridged polyorganosiloxanes have been investigated by solid-state 29Si and 13C solid state NMR in this study. The structures of epoxy-bridged polyorganosiloxanes with respect to the catalysts are quantitatively investigated. Acidic BF3.MEA shows the best catalytic effects on the formation of T3 and D2 structures in the epoxy-bridged polyorganosiloxanes from tri-functional Epoxy-APTES and di-functional Epoxy-APMDS precursors, but basic NBu4.OH has better enhancement on the formation of M1 structure in the epoxy-bridged polyorganosiloxanes from mono-functional Epoxy-APDES precursor. TEM spectra show that the epoxy-bridged polysilsesquioxanes of Epoxy-APTES precursors exhibit polysilsesquioxanes nano domain around 45-55 nm under the catalysis of dibutyltindilaurate (DBTDL), but show bigger polysilsesquioxanes nano domain around 50-150 nm under the catalysis of basic tetrabutylammonium hydroxide (NBu4.OH) in epoxy matrix after direct thermal curing process. In the second part of this study, epoxy-bridged polysilsesquixanes-silica hybrid has been prepared by thermally curing of epoxy-bridged ethoxysilane precursor with various amounts of tetraethoxysilane (TEOS) under the catalysis of boron trifluoridemonoethylamine (BF3MEA) in this study. The epoxy-bridged ethoxysilane precursor was synthesized by reacting one mole of DGEBA epoxy with two moles of 3-Aminopropyltriethoxysilane. BF3MEA shows the best accelerating effect on the formation of -O-Si-O-structure during thermal curing process at 150℃ based 0.1% to 0.2% of TEOS. The effects of boron trifluoride monoethylamine (BF3MEA) on the molecular structures and thermal dynamic properties of cured epoxy-bridged polysilsesquixanes silica hybrid have been investigated. Solid-state 29Si NMR have been used to compare the distribution of both silsesquixanes , T, structures and the silicate , Q, structures of the epoxy-bridged polysilsesquixanes silica hybrid structures cured with or without the catalyst of BF3MEA. Spherical nano silica has been found in the TEM spectra of the epoxy-bridged polysilsesquixanes silica hybrid cured under the catalyst of BF3MEA. Spherical nanosilica with 20 nm of diameter was obtained under 0.1% of BF3MEA catalyst in the cured epoxy-bridged polysilsesquixanes matrix. The lowest coefficient of thermal expansion of the cured epoxy-bridged polysilsesquixanes silica hybrid has been found when 0.1% weight percent of BF3MEA was used as thermal curing catalyst. The glass transition temperatures of the cured epoxy-bridged polysilsesquixanes silica hybrid are no obvious Tgs in TMA and DMA analysis. In the third part of this study, non-aqueous synthesis of nano silica in diglycidyl ether of bisphenol-A epoxy (DGEBA) resin has been successfully achieved in this study by reacting tetraethoxysilane (TEOS) directly in DGEBA epoxy matrix at 80℃four hours under the catalysis of boron trifluoride monoethylamine (BF3MEA). BF3MEA was proved to be an effective catalyst for the formation of nano silica in DGEBA epoxy under thermal heating process. FTIR and 29Si NMR spectra have been used to characterize the structures of nano silica from this direct thermal synthetic process. The morphology of the nano silica synthesized in epoxy matrix has been also analyzed by TEM and SEM spectra. The effects of both the concentration of BF3MEA catalyst and amount of TEOS on the diameters of nano silica in the DGEBA epoxy resin have been discussed in this study. The nano silica containing epoxy exhibited the same curing profile as pure epoxy resin during the curing reaction with 4,4�S-diaminodiphenysulfone(DDS) from DSC analysis. The thermal cured epoxy-nanosilica composites from 40% of TEOS exhibited high glass transition temperature of 221℃, which was almost 50℃higher than pure DEGBA-DDS-BF3MEA cured resin network. Almost 60℃ upgrading of thermal degradation temperature has been observed in the TGA analysis of the DDS cured epoxy-nanosilica composites containing 40% of TEOS. In the fourth part of this study, non-aqueous synthesis of nano silica in polyamideimide(PAI) resin has been successfully achieved in this study by reacting tetraethoxysilane (TEOS) directly in PAI resin solution under the catalysis of boron trifluoride monoethylamine (BF3MEA) at 80℃. FTIR and 29Si NMR spectra have been used to observe and to characterize the structures of nano silica in the polyamideimide resin matrix. Nano silicas with diameters from 30nm to 90nm have been obtained based on different concentrations of BF3MEA catalyst. The thermal drying condition of polyamideimide-silica hybrid solution exhibits obvious correspondence to the thermal stabilities of the polyamideimide-silica hybrid film. The polyamideimide-silica hybrid films dried in air atmosphere exhibit higher thermal degradation temperatures and char yields than those dried in nitrogen atmosphere condition. The Tg of the polyamideimide-silica hybrid film containing 6% of nanosilica appears around 304℃and disappears when the concentration of the silica in the polyamideimide-silica hybrid film reaches 12 wt% from thermal mechanical analysis (TMA). The CTE of the polyamideimide-silica hybrid film also decrease to 43ppm/℃ in polyamideimide-silica hybrid film with 12 wt% of nanosilica. Strong hydrogen bonding interaction between the silanol group of nano silica and the amide groups of PAI resin has been observed in the FTIR analysis. The polyamideimide-silica hybrid film containing 12wt% of nanosilica exhibits tensile strength greater than 250Mpa, which is almost 3 times greater than pure polyamideimide film. The tensile modulus of the polyamideimide-silica hybrid film with 12 wt% naosilica is also found to reach 8.5Gpa. The mechanical strength of the polyamideimide-silica hybrid film increases with the content of naonsilica in the hybrid matrix.