O mecanismo de degradação da solução de poliestirenossulfonato de sódio (PSS) fotossensibilizada por cloreto de 2-hidroxi-3-(3,4-dimetil-9-oxo-9H-tioxanton-2-iloxi)-N,N,N-trimetil-1-propano (QTX) foi investigado. Inicialmente, foi estudada a fotodegradação de QTX em solução aquosa. Os fotoprodutos gerados pela fotólise foram caracterizados em sulfonas e sulfóxidos, que foram identificados por CLAE-EM. A fotodegradação de QTX em solução aquosa foi também acompanhada pelos espectros de absorção UV-Vis, sugerindo a formação de sulfóxidos. As reações elementares de QTX em solução aquosa foram investigadas através da fotólise por pulso de laser. O valor das constantes de supressão do estado triplete de QTX na presença de sorbato de potássio e hidroquinona foram próximas ao valor de constante difusional. A combinação dos resultados obtidos pelas diferentes técnicas possibilitou a proposição do mecanismo para degradação da QTX. A fotodegradação de PSS em solução aquosa na presença e na ausência de QTX foi monitorada por cromatografia de exclusão de tamanho e viscosidade. A fotodegradação de PSS foi observada somente na presença de QTX. Nesta condição uma diminuição de <span style=\"text-decoration: overline\">Mw foi observada, que significa quebra de cadeia aleatória. A degradação PSS/QTX também foi investigada na presença do sorbato de potássio, um supressor de triplete. Neste caso, ocorreu um aumento na porcentagem de degradação. Estes resultados sugeriram que o mecanismo de degradação de PSS fotossensibilizada por QTX ocorre principalmente pela QTX excitada no singlete abstrair um hidrogênio do polímero e na presença de oxigênio leva a formação de radicais, que contribuem para o processo de degradação. / The poly(styrenesulfonate) (PSS) photosensitised by 2-hydroxy-3-(3,4-dimethyl-9-oxo-9H-thioxanthen-2-yloxy)-N,N,N-trimethyl-1-propanium chloride (QTX) solution degradation mechanism was investigated. Initially, the photodegradation of QTX in aqueous solution was studied. The photoproducts generated photolysis were characterized as being sulfones and sulfoxides, which were identified by HPLC-MS. The photodegradation of QTX in aqueous solution was also followed by UV-Vis absorption spectra, suggesting the formation of sulfoxides. The elementary reactions of QTX in aqueous solution were investigated by laser flash photolysis. The quenching rate constant values of the triplet state QTX in the presence of potassium sorbate and hydroquinone were close to the value of diffusion constant. It was possible to propose the mechanism of QTX degradation combining the results from the different techniques. The photodegradation PSS in aqueous solution in the presence and absence of QTX was monitored by size exclusion chromatography and viscosity. The photodegradation of PSS was observed only in the presence of QTX. In this condition a decrease of <span style=\"text-decoration: overline\">Mw was observed, which means the random chain scission. The PSS/QTX degradation was also investigated in the presence of potassium sorbate, a triplet quencher. In this case, an increase of degradation percentage occurred. These results suggested that the degradation mechanism of PSS degradation photosensitised by QTX occurs mainly by the singlet excited QTX abstracts a hydrogen from the polymer and in the presence of oxygen leads to radicals formation which contributed to the degradation process.

Nanocompósitos de poliestirenossulfonato de sódio (PSSNa)/Laponita e PSSNa/SYn-1 foram obtidos através da polimerização do estirenossulfonato de sódio (ESS) fotoiniciada pelo corante safranina O. As interações entre fotoiniciador, monômero e partículas de argila foram caracterizadas por técnicas fotoquímicas, UV vis, fluorescência e fotólise por pulso de laser. A argila Laponita RD altera o comportamento espectral do corante em função da concentração de ESS no meio, sendo que na presença da argila SYn-1 o comportamento continua sendo o mesmo que o observado em solução aquosa. Resultados de espalhamento de raios X a baixo ângulo (SAXS) mostram um aumento do raio de giro das partículas sugerindo uma interação entre as moléculas de monômero e partículas de Laponita RD. A conversão de polimerização de PSSNa em água e em suspensão de argila foi acompanhada por gravimetria e foi observado um aumento de conversão em função da concentração de Laponita RD. Neste caso a porcentagem de conversão aumentou de 11 % em meio aquoso para 39 % em suspensão de Laponita. No caso da argila SYn-1 houve uma redução da porcentagem de polimerização com o aumento da concentração da SYn-1. A combinação dos resultados obtidos pelas diferentes técnicas possibilitou propor que a maior porcentagem de polimerização do ESS em suspensão de Laponita se deve a uma maior concentração local de monômero nas proximidades da partícula de argila. O mesmo efeito não foi observado na suspensão de SYn-1, pois esta argila apresenta uma capacidade de adsorção consideravelmente menor que a Laponita, além disso a Laponita apresenta-se completamente dispersa em meio aquoso, resultando em uma área superficial muito maior. Os compósitos obtidos foram caracterizados por difração de raios X (DRX), microscopia de força atômica (AFM), espalhamento dinâmico de luz (DLS) e espalhamento de raios X a baixo ângulo (SAXS). A técnica de DLS indicou que ocorre uma diminuição do raio hidrodinâmico para as soluções de PSSNa/Laponita com o aumento de porcentagem de Laponita no compósito. As análises dos difratogramas aliadas às imagens de AFM indicaram que existem agregados de Laponita no compósito e que a quantidade desses agregados aumenta com o aumento da porcentagem de argila. / In this work nanocomposites of sodium poly(styrenesulfonate) (PSSNa)/Laponite and PSSNa/SYn-1 were obtained by polymerization of sodium styrenesulfonate (EES) photoinitiated by safranine O. The interactions between, monomer and clay particles were characterized by UV-vis spectroscopy, fluorescence and flash photolysis. Adding laponite to the solution promotes changes in the spectral behavior of the dye as a function of monomer concentration. However, in presence of SYn-1 the spectral behavior of the dye was the same when compared with aqueous media. Small angle X ray scattering indicated an increase of radius of gyration of the laponite particles, suggesting an interaction between monomer and clay. The percentage of conversion of ESS polymerization in aqueous media and clay suspension was studied by gravimetric technique. The yield of the reaction increases with the laponite loading from 11 % to 39% in aqueous media and laponite suspension, respectively. In the case of SYn-1 there was a reduction of polymerization yield as a function of SYn-1 loading. The polymerization of ESS in laponite suspension shows a higher conversion percentage due to the higher local concentration of monomer around clay particles. This effect was not observed in SYn-1 suspension, because this clay has a lower adsorption capacity than Laponite. In addition, Laponite has a complete dispersion in aqueous media resulting in a higher specific surface area than SYn-1. The composites obtained were characterized by X ray diffraction (DRX), atomic force microscopy (AFM) and SAXS. DLS indicated a decrease of the hydrodynamic radio of PSSNa/Laponite particles when increasing Laponite loading. The analysis of diffractograms and AFM images indicated the presence of Laponite aggregates in the composite and its increase with clay loading.

Neste trabalho, materiais nanocompósitos de poli(imida) (PI) derivada de BTDA-pFDA-Mel e argila do tipo montmorilonita, organicamente modificada (O-MMT), foram sintetizados usando a metodologia de two-steps. O componente inorgânico do nanocompósito foi adicionado nas concentrações de 3,3, 5,3 e 8,3% em massa. As membranas sintetizadas foram caracterizadas por Espectroscopia de Absorção na Região do Infravermelho com Transformada de Fourrier (FTIR), Difração de Raio X (DRX), Termogravimetria (TG), Espectroscopia de Fotoelétrons Excitados por Raio X (XPS) e Microscopias Ótica (MO), Eletrônica de Varredura (MEV) e de Transmissão (MET). Os resultados comprovam a formação de PI e uma estrutura de nanocompósito do tipo intercalado, onde a cadeia polimérica expulsa o surfactante do espaço interlamelar; além de apresentar estruturas de argila parcialmente esfoliadas. Os materiais sintetizados foram avaliados como polieletrólito em célula a combustível alcalina (Alkaline Fuel Cell - AFC), obtendo condutividades iônicas em torno de 0,032 S cm-1 e de 0,017 S cm-1 para as membranas de PI pura e de nanocompósito com 3,3% de argila em massa, respectivamente, ambas a 60 &deg;C, as quais são na ordem ou até mesmo superior que os polieletrólitos comercias (Tokuyama&reg;, 0,014 S cm-1) para eletrólito alcalino. Apesar de condutividades razoáveis, a performance obtida para as AFCs em operação não foram satisfatórias, desta forma, membranas de nanocompósitos com PI de cadeia principal de maior mobilidade foram sintetizadas, caracterizadas e avaliadas nas AFCs. Ademais, neste segundo nanocompósito, a adição de grupamentos amino na cadeia principal foram realizados para aumentar a condutividade iônica. Assim, este segundo material apresentou uma maior performance nas AFCs quando comparado com o nanocompósito de PI de cadeia mais rígida e com a membrana comercial Tokuyama&reg; nas mesmas condições. Além disso, a carbonização superficial das amostras foi realizada por meio de tratamento térmico. A formação de estruturas grafitizadas nos materiais de PI pura e dos nanocompósitos foram investigadas por FTIR, DRX, TG, XPS e EPR. Foi encontrado que a formação de estruturas do tipo grafite nas amostras ocorrem principalmente nas primeiras camadas (grafitização superficial), preservando a estrutura interna da poli(imida). Com isso, estruturas poliméricas ou nanocompósitos com superfícies grafitizadas podem atuar tanto como polieletrólitos e ser um caminho promissor para o desenvolvimento de arranjos eletrodo-membrana (Membrane Electrode Assembly - MEA) mais eficientes para células a combustíveis alcalinas, como em processos de catálise heterogênea e processos de separação com membranas. / In this work, Poli(imide)/clay (PI/clay) nanocomposite membranes were synthesized by employing a two-steps method using organically modified montmorillonite clay (O-MMT) with different amounts of O-MMT loading (3.3, 5.3 and 8.3 wt.%). Fourier transform infrared spectroscopy (FTIR), X-ray power diffraction (XRD), thermogravimetric analysis (TG), X-ray photoelectron spectroscopy (XPS), optical microscopy (OM), scanning electron microscope (SEM) and transmission electron microscopy (TEM) measurements, confirmed the formation of pure PI and intercalated-nanocomposite structures. The results revealed parallel clay layers with interlamellar PI and some organoclay partially exfoliated. In addition, the polyelectrolyte membranes of PI and PI/O-MMT (3.3 wt.%) showed that the ionic conductivity were 2- and 1-fold, respectively, higher than that of commercial membrane (Tokuyama&reg;, 0.014 S cm-1), in alkaline fuel cells (AFC) at 60 &deg;C. Despite the fact that the membranes of pure PI and PI/O-MMT demonstrated a good degree of ionic conductivity, rapid fuel cell performance deactivation occurred for the temperature higher than 75 &deg;C. Furthermore, the lack of prepared polyelectrolyte ionic groups, led us to consider alternative synthesis of PI/clay nanocomposite membranes. Thus, the performance for second polyelectrolyte was superior when compared to pure PI, PI/O-MMT and commercial Tokuyama&reg; membranes at same conditions. Moreover, the samples were also surface carbonized by thermal treatment. Combining FTIR, XRD, TG, XPS and electron paramagnetic resonance (ESR) analysis, the results suggested that graphitized nanostructures formation occurred mainly on the surface, maintaining the PI bulk structure. Therefore, graphitized PI/clay membranes may act as one promising way for enhancing both membrane electrode assembly in alkaline fuel cells and gas separation or catalysis.

The slightly water-soluble β-CD and its crystalline inclusion complexes with different molecular weights of poly( ethylene glycol), abbreviated as PEG, were prepared and characterized. The results show that the β -CD forms a crystalline inclusion complex with PEG (MW 600) and PEG (MW 1500) in the solid state. In the solution state, 2D NMR spectroscopy, shows that the PEG is present in the cavity of the P-CD. Coherent cross peaks were observed in both 2D NMR NOESY and ROESY showing correlation between the inner and outer protons of β -CD with the repeating unit of PEG. Scanning electron microscopy (SEM) shows the formation water soluble crystalline complexes between the β -CD with the amorphous PEG (MW 600) and PEG (MW 1500). Crystal formation was supported by wide angle X-Ray studies, W AXD. W AXD patterns for the β-CD/PEG crystalline complexes show new peaks indicative of formation of structures different from the crystalline β-CD.

Drug-resistant pathogens are emerging rapidly and thwart the treatment of common bacterial infectious diseases that can lead to death. Many contagious diseases remain difficult to treat because of acquired drug resistance. Compared to small antibiotics, which interrupt the intracellular biochemical processes, antimicrobial polymers with relatively high molecular weights offer a promising strategy to overcome drug resistance by disrupting the physical integrity of the membrane. Because of the unique mechanism, bacteria need a much longer time to develop resistance. A new class of antimicrobial polymer in which the positive charge and hydrophobic/hydrophilic units are linearly connected in the amidinourea backbone was designed, synthesized, and tested for various bacteria including methicillin-resistant Staphylococcus aureus (MRSA). We evaluated the effects of hydrophobicity and polymer molecular weights on antimicrobial activity by measuring minimum inhibitory concentrations (MIC) and hemolytic activities (HC50). Amidinourea antimicrobial polymers exhibit a promising MIC90 value (13 μg/mL) with low HC50, resulting in high selectivity (HC50/MIC90) against MRSA. Many bacteria have developed resistance against Ciprofloxacin. To overcome the antibiotic resistance associated with Ciprofloxacin, we hypothesized that a steady release of Ciprofloxacin at the bacteria membrane can overcome the drug resistance because the local drug concentration can be overwhelmingly high to suppress the drug efflux pump expressed on the membrane. A series of homo and di-block copolymers containing Ciprofloxacin, as the form of prodrugs, was synthesized using ring-opening metathesis polymerization (ROMP), and we evaluated their antimicrobial efficacy.While homo polymers only containing Ciprofloxacin were inactive against almost all bacteria tested, di-block copolymers containing Cipro and triphenylphosphine exhibited some antimicrobial activity against wild type M. smegmatis. Modulation of chemical environments at the positively charged polymeric materials can significantly influence the biophysical properties required for efficient cellular interaction and subsequent entry. Using intrinsic fluorescent conjugated polymers (CPs), we have demonstrated that the modulated guanidine group with various hydrophilic or hydrophobic moieties dramatically changed their cellular behaviors. We prepared a series of modified guanidine-containing CPs and examined their cellular behaviors by using confocal microscopic imaging. Details of the modification chemistry and modification-dependent cellular behaviors and a knockdown of a target protein in primary cells were discussed.

Research Doctorate - Doctor of Philosophy (PhD) / The photochemistry of poly{p-phenylene[1-(tetrahydrothiophen-1-io)ethylene chloride]} (PPTEC), a water soluble precursor of the semiconducting polymer, poly{p-phenylenevinylene} (PPV), has been studied both under atmospheric conditions and in environments devoid of oxygen. UV-visible spectroscopy and photoluminescence data has been used to provide a picture of the mechanistic pathways involved in UV irradiation of the PPTEC material. A new quantitative model for the effect of UV irradiation upon film morphology is presented. The technique of near-field scanning optical lithography (NSOL) has been used to produce arbitrary structures of the semi-conducting polymer poly{p-phenylenevinylene} at sizes comparable with optical wavelengths. Structures on this scale are of interest for integrated optical devices and organic solar cells. The structures are characterised using AFM and SEM and examined in the context of the electric field distribution at the NSOM tip. The Bethe-Bouwkamp model for electric field distribution at an aperture has been used, in combination with the developed model for precursor solubility dependence on UV energy dose, to predict the characteristics of lithographic features produced by NSOL. Fine structure in the lithographic features that are characteristic of the technique are investigated and their origins explained. Suggestions for the improvement of the technique are made. Presented here for the first time is a device manufactured by the technique of NSOL functioning as an optical device. The technique of NSOL is used to manufacture an optical transmission phase grating (or phase mask) of PPV, this was done as a proof of concept for device manufacture by this method and to demonstrate the potential usefulness of the unique characteristics of the technique. The phase mask was characterised using AFM and SEM and examined in the context of how well a diffraction pattern matches with theoretical calculations.

Thèse (M.Sc.)--Université Laval, 2005. / Bibliogr.: f. 75-90. Publié aussi en version électronique.

Nanoscale patterning of organic molecules has received considerable attention in current nanoscience for a broad range of technological applications. In order to provide a viable approach, this thesis describes catalytic stamp lithography, a novel soft-lithographic process that can easily produce sub-100 nm patterns of organic monolayers on surfaces. Catalytic stamps were fabricated through a two-step procedure in which the nanoscale patterns of transition metal catalysts are first produced on SiOx/Si surfaces via the use of self-assembled block-copolymers, followed by the production of the poly(dimethylsiloxane) (PDMS) stamps on top of the as-patterned metals. Simply peeling off the as-formed PDMS stamps removes the metallic nanostructures, leading to the functional stamps. A number of different patterns with various metals were produced from a commercially available family of block copolymers, polystyrene-block-poly-2-vinylpyridine, by controlling the morphology of thin-film templates through the modulation of molecular weights of polymer blocks or solvent vapor annealing. Using these catalytic stamps, hydrosilylation-based catalytic stamp lithography was first demonstrated. When terminal alkenes, alkynes, or aldehydes were utilized as molecular inks, the metallic (Pt or Pd) nanopatterns on catalytic stamps were translated into corresponding molecular arrays on H-terminated Si(111) or Si(100) surfaces. Since localized catalytic hydrosilylations took place exclusively underneath the patterned metallic nanostructures, the pattern formations were not affected by ink diffusion and stamp deformation even at the sub-20 nm scale, while maintaining the advantages of the stamp-based patterning (i.e., large-area, high-throughput capabilities, and low-cost). The concept of catalytic stamp lithography was further extended with other catalytic reactions, and successful nanoscale patterning was performed using hydrogenation (on azide-terminated SiOx surfaces) and the Heck reaction (on alkene- or bromphenyl-terminated SiOx surfaces). A range of nanopatterned surfaces with different chemical functionalities, including thiol, amine, and acid, were created, and they were further modified through appropriate chemical reactions. The potential utility of this simple approach for the construction of a higher degree of nanoarchitectures was suggested.

Notre recherche se base sur la structuration des polymères conjugués qui présentent des propriétés optiques et électroniques intéressantes en raison de leur structure moléculaire intrinsèque. En effet, la structure des polymères conjugués se compose d’une alternance de simples et de doubles liaisons donnant lieu à une délocalisation des électrons le long des chaînes. Cette conjugaison est à l’origine de leurs propriétés de luminescence et de leur caractère semi-conducteur. Ces polymères sont couramment utilisés dans des dispositifs électroniques où ils jouent le rôle de composant actif. Le fonctionnement de ces dispositifs repose sur la capacité des charges à se déplacer le long des chaînes (processus intramoléculaire) et d'une chaîne à l'autre (processus intermoléculaire) et par conséquent, ces propriétés de transport dépendent de l’arrangement des chaînes polymères dans le solide, qui lui-même découle des interactions supramoléculaires. Il est donc impératif de maîtriser ces interactions et d’étudier l’influence qu’elles ont sur les performances de tels dispositifs électroniques. C’est précisément sur ce point que porte notre travail : étudier et contrôler la formation de nanostructures en termes de dimensions, de forme et de localisation, en appliquant une contrainte physique extérieure à un film de polymère conjugué. Le polymère conjugué sur lequel notre étude se base principalement est le poly(3-hexylthiophène), P3HT. Ce polymère est semi-cristallin et possède une mobilité de charge élevée (0.18 cm2/V.s), ce qui en fait un très bon candidat en tant que composant actif dans les transistors à effet de champ. Nous avons, dans le cadre de notre recherche, étudié la structuration de films minces de P3HT, réalisée par l’application de contraintes physiques extérieures. L’utilisation d’une pointe de microscope à force atomique travaillant en mode contact permet de déformer plastiquement la surface polymère en créant des structures périodiques en surface des films mais elle permet, en outre, d’orienter les chaînes polymères dans la direction de passage de la pointe. Différents paramètres expérimentaux ont été étudiées comme par exemple, la résolution choisie pendant l’expérience, le nombre de passage effectués par la pointe ou encore l’angle avec lequel la pointe structure le film polymère. Nous avons également démontré que cette technique, appliquée au canal polymère d’un transistor à effet de champ, permet d’améliorer les propriétés électriques du P3HT et par conséquent, d’augmenter les performances du dispositif électronique. Nous avons utilisé une autre méthode, dite de « lithographie douce », afin de structurer le P3HT. Cette technique présente l’avantage de « façonner » le polymère lorsqu’il se trouve en solution et ne nécessite donc pas la formation préalable d’un film. Elle consiste à déposer une goutte de solution polymère sur un substrat, à l’entrée de canaux micrométriques de PDMS; l’écoulement de la solution polymère, qui se fait par capillarité dans les canaux, est donc confiné. Le solvant va ensuite s’évaporer et il reste alors, sur le substrat, un dépôt polymère qui est la réplique négative des canaux de PDMS. L’analyse du dépôt polymère formé grâce à cette méthode révèle, comme c’était le cas pour la technique précédente, une orientation des chaînes polymères au sein des canaux. Dans la dernière partie de ce travail, nous avons étudié le dopage de films fibrillaires de P3HT. L'étude de la morphologie des films dopés montre que la structure fibrillaire est conservée, avec une légère augmentation de la largeur des fibrilles. Cette augmentation résulte d'un déplacement des chaînes polymères les unes par rapport aux autres dans l'axe du squelette conjugué afin de laisser des espaces vacants pour accueillir les contre-ions dans le réseau polymère. Les mesures électriques des films dopés montrent un accroissement très important de la conductivité du polymère. On observe une augmentation de six ordres de grandeur entre les conductivités d'un film neutre et dopé.

Ce travail porte sur l'étude de revêtements polysilazane (PSZ) élaborés dans le but d'inhiber l'adhésion des bactéries marines. Deux stratégies ont été étudiées : le greffage de chaînes poly(oxyde d'éthylène) (POE) (350, 750 ou 2000 g/mol) sur les chaînes PSZ par réactions d'hydrosilylation d'une part, et l'incorporation de composés du cuivre dans un film céramique issu de la pyrolyse d'un précurseur PSZ, d'autre part. Les conditions optimales de synthèse des PSZ greffés POE ont été définies afin de limiter notamment la réaction d'isomérisation de l'allyl-POE. La réticulation des PSZ greffés POE est alors effectuée par voie humide à température ambiante et procède par hydrolyse-condensation des fonctions alcoxysilane, SiH et SiN du précurseur PSZ. La prédominance des Si de type T3 (RSi(OSi)3) a été mise évidence par spectrométrie RMN du 29Si à l'état solide. La cristallisation des chaînes courtes de POE (350 g/mol) est totalement inhibée alors que l'aptitude des chaînes longues POE (750 et 2000 g/mol) à cristalliser est préservée. Le caractère hydrophile-hydrophobe et la capacité des films à inhiber l'adhésion bactérienne a été étudiée sur des revêtements à densités de greffons et à longueur de chaînes POE différentes. Les PSZs greffés POE 350g/mol avec un taux de greffage maximal conduisent à l'activité bactérienne la plus élevée de l'ensemble des revêtements étudiés.Les films céramiques incorporant du cuivre ont été préparés par pyrolyse d'un oligovinylsilazane en présence d'acétylacétonate de cuivre II sous atmosphère oxydante ou non oxydante. L'identification des phases des composés du cuivre a été effectuée par analyse DRX. L'environnement réducteur généré lors de la pyrolyse du PSZ favorise la formation d'espèces de cuivre (0) et cuivre (I) au détriment de cuivre (II). Les études bactériennes suggèrent que les cristaux CuO et Cu2O sont plus efficaces que le cuivre métal pour lutter contre l'adhésion bactérienne.