Universiẗat, Diss., 2004--Mainz.

Although, the use of vinyl pyridine polymers, especially as matrices for nanoparticle synthesis, is growing considerably, the knowledge of thermal degradation behavior is still missing in the literature. In this study, thermal degradation characteristics of the homopolymers / poly(4-vinylpyridine), P4VP, and poly(2-vinylpyridine), P2VP, the diblock copolymers / polystyrene-blockpoly( 2-vinylpyridine), (PS-b-P2VP) and polystyrene-block-poly(4-vinylpyridine), (PS-b-P4VP), and the metal functional vinyl polymers / cobalt-polystyrene-blockpoly( 2-vinylpyridine) and cobalt-polystyrene-block-poly(4-vinylpyridine) were investigated by direct pyrolysis mass spectrometry. The effects of the position of the nitrogen in the pyridine ring, composition and molecular weight of diblock copolymer and coordination of the metal to the pyridine ring of the copolymer on thermal behavior were also investigated. The results showed that unlike most of the vinyl polymers that decompose via depolymerization, P2VP degrades through opposing reaction pathways / depolymerization, proton transfer to N atom in the pyridine ring yielding unsaturated linkages on the polymer backbone that decompose slightly at higher temperatures and loss of pyridine units. On the other hand the thermally less stable P4VP decomposition follows v depolymerization in accordance to general expectations. Another finding was the independent decomposition of both components of the diblock polymers, (PS-b- P2VP) and (PS-b-P4VP). Thermal degradation occurs in two main steps, the thermally less stable P2VP or P4VP chains degrade in the first step and in the second step decomposition of PS takes place. It was also concluded that upon coordination of metal, thermal stability of both P2VP and P4VP increases significantly. For metal functional diblock copolymers thermal degradation of chains coordinated to Co metal through N in the pyridine ring occurred in three steps / cleavage of pyridine coordinated to Co, coupling and H-transfer reactions yielding unsaturated and/or crosslinked structure and decomposition of these thermally more stable unsaturated and/or crosslinked blocks. TEM imaging of the metal functional block copolymers along with the results of the pyrolysis mass spectrometry pointed out that PS-b-P2VP polymer is a better and more effective matrix for nanoparticle synthesis.

Polyaniline (PAn) is an important conjugated conducting polymer because of its good environmental stability. However, the conductive form of polyanilune is difficult to processed because it is insoluble in common organic solvent. This property limits its processibility and application. In the study, we developed a feasible route for preparing polyaniline/surfactant core-shell latex to solve the insoluble problem. The polyaniline latex was made by emulsion polymerization of aniline monomer, using ionic polymer (poly(4-vinylpyridine)-methanesulfonic acid; P4VP(MSA)) as the surfactant and dopant. And then, the nano-size and core-shell morphologies of polyaniline latex was studied by Transmission electron microscopy (TEM) technique. The best conductivity of polyaniline film is approach to 10-2 S/cm.

Techn. Universiẗat, Diss., 2004--Darmstadt.

No description available.

Orientadores: André Luiz Barboza Formiga, Maria Isabel Felisberti / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-20T16:07:14Z (GMT). No. of bitstreams: 1 Jannuzzi_SergioAugustoVenturinelli_M.pdf: 35610656 bytes, checksum: f2dffeb8cf285399ac0996a04b2601a7 (MD5) Previous issue date: 2011 / Resumo: O presente trabalho ocupa-se da síntese, caracterização e aplicação de um material híbrido orgânico-inorgânico em que o bloco orgânico é o polímero poli(4-vinilpiridina) e o bloco inorgânico é o pentacianoferrato(II) de sódio. A primeira parte trata da influência do polímero nas propriedades do complexo, e vice-versa. A segunda parte ilustra a aplicação do metalopolímero na produção de estruturas análogas ao azul da Prússia (AP) pela reação de Fe com as unidades pentacianoferrato. A banda de transferência de carga metal-ligante do pentacianoferrato do metalopolímero em solução desloca-se para energias menores na medida em que aumenta a fração de meros livres da cadeia polimérica, indicando que a fração do bloco orgânico modula a polaridade do ambiente químico do complexo. Por outro lado, a crescente quantidade de complexo ligado às cadeias poliméricas aumenta viscosidade das soluções de metalopolímeros, evidenciando que o pentacianoferrato expande o novelo macromolecular. Estruturas tipo azul da Prússia sintetizadas a partir do metalopolímero exibem elevada estabilidade coloidal quando comparadas aos compostos isentos de polímero e apresentam banda de intervalência em menores energias do que o frequentemente reportado para esse tipo de estrutura, provavelmente em virtude do envolvimento das partículas de AP pelo polímero / Abstract: This work comprises the synthesis, characterization and application of a hybrid organic-inorganic metallopolymer, in which the organic block is the polymer poly(4-vinylpyridine) and the inorganic block is the complex sodium pentacyanoferrate(II). The first part presents the influence of the polymer on the properties of the complex and vice-versa. The second part illustrates an application of the metallopolymer on the production of Prussian blue (AP) analogs based on the reaction of Fe with the pentacyanoferrate moieties. The metal-to-ligand charge transfer band of the polymer-bound pentacyanoferrate in solution shifts towards lower energies whereas the free monomers fraction arises. It indicates that the organic block fraction tunes the polarity of the pentacyanoferrate chemical environment. On the other side, the increasing fraction of complex bound to the polymer chain increases the metallopolymer solution viscosities. This is an evidence that the pentacyanoferrate expands the macromolecular coil. Prussian blue-type structures synthesized from metallopolymers exhibit enhanced colloidal stability when compared to the polymer-free compounds. They also present intervalence bands at lower energies than those frequentlly reported for this type of inorganic structure. The reason is probably the polymer wrapping of the particles / Mestrado / Quimica Inorganica / Mestre em Química

Les recherches effectuées dans le cadre de cette thèse portent sur l'étude du mécanisme de la polymérisation anionique syndiospécifique des monomères vinyliques polaires, la 2-vinylpyridine étant prise comme modèle, en présence d'acides de Lewis organo-aluminiques. L'intérêt d'une étude sur la 2-vinylpyridine, réside essentiellement dans la bonne stabilité des centres actifs issus de sa polymérisation en milieu non polaire, qui conduisent à des systèmes "vivants" au sens défini par SZWARC. Dans un premier temps, l'analyse des résultats issus du suivi cinétique de la propagation par calorimétrie adiabatique ainsi que de la caractérisation par R.M.N. ( 1 H, 13C) de modèles des espèces actives présentes dans le milieu réactionnel, en absence d'acide de Lewis, ont permis de conclure à une polymérisation s'effectuant de manière prépondérante sur des paires d'ions intimes, non agrégées, selon un mécanisme analogue à celui proposé, précédemment, dans le cas d'un amorçage par les organo-magnésiens. Dans un deuxième temps, une démarche expérimentale identique a permis de montrer que, en présence de AlEt3, les espèces actives se présentent principalement sous forme monomère, complexées au dérivé organo-aluminique par l'intermédiaire de l'atome d'azote du motif ultime de la chaîne en croissance. Par ailleurs, l'étude de la tacticité des polymères préparés en présence de AlEt3 indique que le mécanisme d'addition d'une unité monomère sur le centre actif suit une loi statistique de type "bemouillien". Enfin, les faibles taux de syndiotacticité, mesurés sur ces polymères, montrent que la polymérisation anionique de la 2-vinylpyridine n'est que très peu syndiospécifique par rapport à celle du méthacrylate de méthyle obtenue dans les mêmes oonditions. Le mécanisme syndiorégulateur proposé, fait intervenir uniquement l'approche du monomère sur le motif ultime de la chaîne en fonction de la gêne stérique imposée par le complexe "centre actif AlEt3".

Structural changes of electroactive species during electrochemical reactions cannot be determined from the electroanalytical technique alone. By incorporating spectroscopic techniques with electrochemistry, additional information about analyte structure and composition of the double layer can be obtained during electrochemical processes. Several spectroscopic methodologies have been tailored for this purpose including electronic and vibrational spectroscopies. Mid-infrared ATR spectroscopy is especially interesting as it provides in-situ information about adsorbates at the electrode surface. Mass transport limitations present in mid-infrared (mid-IR) external reflection and transmission spectroelectrochemistry are circumvented with attenuated total reflectance (ATR) spectroelectrochemistry. However, limitations of appropriate electrode materials for internal reflection configurations have hindered widespread adoption of the technique. The work described in this thesis focuses on the development and coupling of electrically conducting DLC films with mid-IR transparent multi-reflection waveguides for ATR spectroelectrochemistry. Conducting diamondlike carbon (DLC) thin films were developed utilizing pulsed laser deposition systems in collaboration with Joanneum Research (Leoben, Austria) and at the University of North Carolina (Chapel Hill). Nitrogen doping and incorporation of noble metal nanoclusters were investigated as approaches aimed at improving the electrical conductivity of DLC. Detailed compositional studies of nitrogen-doped DLC layers showed that sp2-hybridized carbon is responsible for the observed electrochemical activity. Optical transparency of thin (~ 40 nm) DLC layers in the mid-IR regime was confirmed by transmission-absorption measurements upon deposition on zinc selenide ATR waveguides. Additionally, the first spectroelectrochemical application of conducting DLC films was demonstrated via the electropolymerization of polyaniline onto coated ATR elements. Metal-DLC nanocomposite layers were investigated with various analytical techniques obtaining detailed compositional information. Improved electrochemical activity of metal-DLC demonstrated their suitability as electrode materials. Sufficient mid-IR transmissivity of metal-DLC coated germanium waveguides was displayed to enable spectroelectrochemical application. Finally, electropolymerization of poly(4-vinylpyridine) in acetonitrile was pursued to produce highly cross-linked ion-exchange membranes for spectroelectrochemical sensing. The composition of the pre-polymerization mixture and deposition conditions were tailored to obtain uniform semipermeable membranes. Diffusion of cations to electrodes is restricted by performing the electropolymerization as established herein. By employing the described electropolymerization procedure at DLC-coated waveguides, spectroelectrochemical sensing strategies can now be extended into the mid-IR regime.

Asymmetric polymeric materials can be formed by either top-down or bottom-up methods. Bottom-up methods involve assembling the atoms and molecules to form small nanostructures by carefully controlled synthesis, which results in a reduction of some of the top-down limitations. In this dissertation, thermal, tribological and antireflective properties of polymeric materials have been enhanced by introducing structural asymmetry. The overall performance of commercial polymeric coatings, e.g. epoxy and polyvinyl chloride, has been improved by conducting the blending methods, specifically, chemical modification (α,ω-dihydroxydimethyl(methyl-vinyl)oligoorganosiloxane), cross-linking (triallyl isocyanurate), and antioxidant (tris(nonylphenyl) phosphite) incorporation. The nonequilibrium polymeric structures (moth-eye and square array) have been developed for the ultrahigh molecular weight block copolymers via the short-term solvent vapor annealing self-assembly. The large domain size of the moth eye structure allows for improvement of the light transmittance particularly in the visible and near infrared ranges, while the square arrangement of the block copolymer opens the possibility of magnetic data storage application by the large magnetic nanoparticles' embedment or masking of the superconductors.

Nanoscale particles based on the nature of building blocks often self-assemble into superstructures with distinctive spatial arrangements which can be used as functional materials for different application. Micro-phase separated hairy nanoparticle with helical hair can self-assemble to form supramolecular material which may mimic the properties and functions of the natural polymers such as protein and cellulose. Beside this hairy/core-shell nanoparticles also may find many applications such as in asymmetric catalysis, nano-fillers in tire and rubbers, model systems for biology, lithography and as sensors. In this work, we have successfully synthesized two hairy nanoparticles both of which has cross-linked polystyrene core with helical poly (3- methyl 4- vinyl pyridine) and poly (2- methoxystyrene) brushes respectively by living anionic polymerization via one-pot synthesis. NMR spectroscopy was used to determine that polymerization was successful and compositions of HNPs have the agreement with the targeted HNPs structure. By tailoring the architecture (functionalization of polymer chains, the degree of polymerization, grafting density) of HNPs, it is possible to control the final properties of the system. Differential Scanning Calorimetry was used to demonstrate the thermal properties of the synthesized HNPs which corresponds to polymer composition. Dynamic light scattering, SEM and AFM images were recorded to measure the particle size and morphology of the particles. Circular dichroism spectroscopy was used to determine the induced chirality of helical polymer brushes by complexing it with the small chiral molecule. SEM and AFM imaging were recorded to find out the morphology and hierarchically self-assembly of the hairy nanoparticle system. The synthesized particles may have great potential to successfully generate self-assembled suprastructures which can further solve the chiral resolution problem and can also find different applications.