Zugl.: München, Techn. Univ., Diss., 2009.

Indiana University-Purdue University Indianapolis (IUPUI) / The purpose of this laboratory study was to determine whether etching of flat bovine enamel surfaces with a 50 per cent aqueous solution of phosphoric acid for 60 seconds increases the bonding of a conventional restorative acrylic resin and a new polycarboxylate cement. The test specimens were subjected to 24 hours, 30 days and six months storage in water and then subjected• to temperature stress cycling and intermittent tensile stress cycling. A tensile test was used to measure the bond strength of both materials. The results of the Newman-Keul's test showed that pretreating the enamel surface with 50 per cent phosphoric acid significantly increased the bonding of the restorative resin, and that the cavity sealer supplied by the manufacturer further improved the resin attachment to enamel surfaces previously etched with phosphoric acid. The bonding of the resin to acid-etched enamel surfaces pretreated with or without the cavity sealer was unaffected by prolonged storage in water, temperature stress cycling, and intermittent tensile stress cycling. However, a significant reduction in the adhesion of the acrylic resin to polished-enamel surfaces pretreated with or without the cavity sealer was observed when the test specimens were subjected to the same testing conditions. The data obtained for the polycarboxylate cement test specimens showed that etching of the enamel surface with phosphoric acid also provided slightly higher adhesive values than the control specimens. Results obtained revealed that prolonged storage in water, and temperature and mechanical stress cycling did not affect the adhesion of the polycarboxylate cement to acid-etched enamel surfaces. However, thermal and mechanical stress cycling after prolonged storage in water appeared to decrease the adhesion of the cement to polished enamel surfaces. When Ca45 was used to assess the marginal seal of resin restorations placed into acid-etched Class V cavity preparations in extracted human teeth, the autoradiographs showed that etching of the cavity preparations with 50 per cent phosphoric acid improved the marginal seal of the restorative resin after one-week storage in water. When both the acid-etched and control restorations were thermal stress cycled 2500 times at a 40°C temperature differential, a slight improvement in the marginal seal of the acid-etched restorations was observed.

Les superplastifiants sont des adjuvants développés pour conférer aux matériaux cimentaires une plus grande fluidité pour un même rapport eau/ciment (E/C) en favorisant la dispersion des particules. De nombreuses études ont été réalisées pour approfondir la compréhension de leur mode d'action. La plupart du temps, elles relient directement la quantité adsorbée au comportement rhéologique des matériaux dans lesquels ils sont incorporés. Cependant, à une échelle intermédiaire, l'organisation mésostructurale de la pâte cimentaire contrôle non seulement sa fluidité, mais également son homogénéité et sa stabilité physicochimique.Ces travaux de thèse portent sur une dernière génération de superplastifiant : les polycarboxylates (PCE). Une approche expérimentale multi-échelles a été développée en intégrant les caractéristiques mésostructurales de la pâte de façon à faire le lien entre les interactions organo-minérales, notamment l'adsorption des PCE, et les propriétés macroscopiques (comportements en sédimentation et rhéologique). L'identification et la caractérisation granulaire de la pâte a été abordée à l'échelle de la particule, par une approche morpho-granulométrique. Des indices de dispersion ont été définis de façon à quantifier l'influence des PCE sur l'organisation mésostructurale des particules (particules unitaires ou agglomérées). Dans un second temps, l'évolution de cette organisation a été étudiée par l'analyse des colonnes de sédimentation. Un indice de séparation de phase a été défini, mettant en évidence l'existence de plages de stabilité en fonction du dosage et de la structure moléculaire du PCE incorporé.La mise en relation de ces observations avec l'étude des interactions organo-minérales a permis d'approfondir la compréhension du mode d'action et de l'influence des PCE. Cette démarche analytique représente un outil potentiel au développement de superplastifiants novateurs. / Superplasticizers are admixtures developed to give the cementitious materials greater fluidity for the same water to cement ratio (w/c), promoting the particles dispersion. Many studies were conducted to deepen the understanding of their mode of action. Usually, they connect directly the amount adsorbed with the rheological behavior of the materials in which they are incorporated. However, at an intermediate scale, mesostructurale organization of the cement paste controls not only its fluidity, but also its homogeneity and physicochemical stability.This work focuses on a new generation of superplasticizers: polycarboxylates (PCE). A multi-scale experimental approach has been developed by integrating mesostructural characteristics of cement paste to make the link between the organo-mineral interactions, particularly PCE adsorption, and the macroscopic properties (sedimentation and rheological behavior). Identification and granular characterization of cement paste was discussed, at the level of the particle, by a morpho-granulometric approach. Dispersion indices were defined to quantify the influence of PCE on mesostructural organization of particles (unit particles or agglomerates). In a second step, the evolution of this organization has been studied by analysis of sedimentation columns. A phase separation index has been defined, highlighting the existence of stability ranges as a function of the dosage and molecular structure of the PCE incorporated.Linking these observations with study of organo-mineral interactions has allowed to deepen the understanding of the mode of action and influence of PCE. This analytical approach is a potential tool to the development of innovative superplasticizers.

La résistance mécanique des bétons exigée actuellement impose une diminution du rapport eau/ciment et l’utilisation de superplastifiant pour faciliter la mise en œuvre du matériau frais. Les produits de type polycarboxylate sont très efficaces à court terme, mais peuvent mener à une perte rapide de l’ouvrabilité en cas d’incompatibilité liant/superplastifiant. L’objet de ce travail est l’identification des phases cimentaires impliquées dans ces variations rhéologiques. Dans un premier temps, l’écoulement de pâtes superplastifiées est évalué par un rhéomètre muni d’un système de mesure à boule. Les combinaisons compatibles s’écoulent selon le modèle de Bingham. Une incompatibilité entraîne soit une augmentation du seuil d'écoulement et de la viscosité plastique, soit une évolution des propriétés rhéologiques en un fluide d’Herschel-Bulkley. Dans un deuxième temps, des combinaisons ciment/superplastifiant sont caractérisées par des essais rhéologiques. L’évaluation du raidissement de pâtes et la caractérisation chimique des ciments hydratés montrent que la consistance est liée à la quantité et à la microstructure de l’ettringite formée. Ces paramètres dépendent de la phase aluminate et des sulfates de calcium initialement présents. Enfin, l’étude de systèmes cimentaires de synthèse établit que la solubilité des sulfates de calcium en présence de superplastifiant est augmentée du fait, vraisemblablement, de la complexation des ions Ca2+ par les polycarboxylates. La variété orthorhombique de la phase aluminate plus réactive que la variété cubique, mène, quant à elle, à la formation d’une quantité importante d’ettringite en forme d’aiguilles / Currently required concrete strength imposes a lower water/cement ratio and use of superplasticizer to make easier the fresh material implementation. Polycarboxylate type products are very effective in the short term but can lead to a fast loss of workability in case of binder/superplasticizer incompatibility. The object of this work is the identification of cementitous phases involved in these rheological variations. Initially, flow of various superplasticized pastes is evaluated by a rheometer fitted with a ball measuring system. Compatible combinations flow like a Bingham’s fluid. An incompatibility results in an increase of yield stress and plastic viscosity or rheological properties evolution into Herschel-Bulkley’s fluid. Then, cement/superplasticizer combinations are characterized by rheological tests. Stiffening assessment of pastes and chemical characterisation of hydrated cements show that consistency is associated with amount and microstructure of formed ettringite. These parameters depend on initially present aluminate phase and calcium sulphates. Finally, study of synthetic cementitous systems states that calcium sulphates solubility, in presence of superplasticizer, is increased probably because Ca2+ ions complexation by polycarboxylates. As for the orthorhombic variety of aluminate phase, more reactive than cubic variety, it leads to a large amount of needle-shaped ettringite

Les superplastifiants sont des adjuvants développés pour conférer aux matériaux cimentaires une plus grande fluidité pour un même rapport eau/ciment (E/C) en favorisant la dispersion des particules. De nombreuses études ont été réalisées pour approfondir la compréhension de leur mode d'action. La plupart du temps, elles relient directement la quantité adsorbée au comportement rhéologique des matériaux dans lesquels ils sont incorporés. Cependant, à une échelle intermédiaire, l'organisation mésostructurale de la pâte cimentaire contrôle non seulement sa fluidité, mais également son homogénéité et sa stabilité physicochimique.Ces travaux de thèse portent sur une dernière génération de superplastifiant : les polycarboxylates (PCE). Une approche expérimentale multi-échelles a été développée en intégrant les caractéristiques mésostructurales de la pâte de façon à faire le lien entre les interactions organo-minérales, notamment l'adsorption des PCE, et les propriétés macroscopiques (comportements en sédimentation et rhéologique). L'identification et la caractérisation granulaire de la pâte a été abordée à l'échelle de la particule, par une approche morpho-granulométrique. Des indices de dispersion ont été définis de façon à quantifier l'influence des PCE sur l'organisation mésostructurale des particules (particules unitaires ou agglomérées). Dans un second temps, l'évolution de cette organisation a été étudiée par l'analyse des colonnes de sédimentation. Un indice de séparation de phase a été défini, mettant en évidence l'existence de plages de stabilité en fonction du dosage et de la structure moléculaire du PCE incorporé.La mise en relation de ces observations avec l'étude des interactions organo-minérales a permis d'approfondir la compréhension du mode d'action et de l'influence des PCE. Cette démarche analytique représente un outil potentiel au développement de superplastifiants novateurs.

[pt] O magnetismo molecular tem despertado muito interesse devido a possível aplicação em componentes de materiais eletrônicos. Esses tipos de materiais podem ser criados através de compostos de coordenação, como os polímeros de coordenação, que têm a capacidade de serem materiais multifuncionais. Neste trabalho foram sintetizados 11 compostos inéditos, divididos em dois sistemas que diferem conforme a composição dos materiais. O primeiro sistema utilizou a mistura do ligante policarboxilato BTB e do ligante N-doador como phen e dmdpy para avaliar a influência desses ligantes auxiliares na estrutura e propriedades dos complexos. A família que utiliza fen como ligante auxiliar gerou dois polímeros de coordenação isomorfos 1D com Cu(2+) e Co(2+) como íons metálicos. Medições de EPR para o polímero Cu(2+) não mostraram quase nenhuma interação magnética entre íons metálicos. Devido ao fato de ambos os CPs serem isomorfos, as mesmas pequenas interações magnéticas eram esperadas para o Co(2+) CP, o que é um indicativo do possível comportamento da molécula magnética devido ao forte ZFS de cobalto. A medição da suscetibilidade magnética fora de fase mostrou o comportamento do nanoímã. Um tempo de relaxação de tensão no ponto de escoamento = 5,52(4) × 10(-7)s e barreira de energia de 12,1(3) K foram determinados para este complexo. A mudança do ligante doador de N de phen para dmdpy resultou em um dímero de Cu(2+)pentacoordenado, porém, como o ligante divergente para ambas as famílias era o mesmo, a pequena interação entre os íons cobre(II) foi obtida, como evidenciado por EPR e magnetização medições. O segundo sistema apresenta íons Ln(3+) com ácido cumarínico-3-carboxílico como ligante orgânico, onde duas famílias diferentes foram obtidas alterando a proporção de íons Ln e ligante. A primeira família 1D CP foi obtida com ambos os componentes na mesma proporção. Estudos magnetocalóricos foram realizados para o Gd(3+) e o valor de entropia magnética máxima obtido foi menor que o valor esperado. Para os CPs Tb(3+) e Dy(3+) apresentaram potencial como nanoímãs devido ao sinal obtido nas medidas magnéticas dinâmicas. Foram realizados estudos fotoluminescentes para CPs Eu(3+) e Tb(3+), onde foram estimados tempos de vida de emissão de 0,30 ± 0,05 ms e 0,13 ± 0,05 ms. A segunda família obtida apresentou proporção de Ln(3+) e 3-HCCA de 1:3, e resultou em um polímero de coordenação 1D, onde a extensão da cadeia polimérica teve o mesmo mecanismo. Foram realizados estudos fotoluminescentes para CPs Eu(3+) e Tb(3+), onde foi observado um aumento no tempo de vida da emissão de 0,30 ± 0,05 ms para 0,45 ± 0,05 ms para o derivado Eu(3+) devido à remoção de uma molécula de H2O coordenada ao íon európio. Este trabalho resultou, até o momento desta dissertação, na publicação de dois artigos científicos, além de outro adicional que está em processo de review. / [en] Molecular magnetism has created a lot of interest due to its possible application in components of electronic materials. These types of materials can be created through coordination compounds such as coordination polymers, which have the capacity to be multifunctional materials. In this work, we synthesized a total of 11 new complexes organized in two systems that differ according to the composition of materials. The first system utilized the mixture of polycarboxylate ligand BTB and N-donor ligand such as phen and dmdpy to evaluate the influence of these auxiliary ligands in the complexes structure and properties. The family utilizing phen as auxiliary ligand generated two isomorph 1D coordination polymers with Cu(2+) and Co(2+) as metal ions. EPR measurements for Cu(2+) polymer showed almost no magnetic interactions between metal ions. Due to both CPs being isomorph, the same small magnetic interactions were expected for Co(2+) CP, which is an indicative of possible magnetic molecule behavior due to cobalt strong ZFS. Out-of-Phase magnetic susceptibility measurement showed the nanomagnet behavior. A relaxation time of yield point stress = 5.52(4) × 10(-7) s and energy barrier of 12.1(3) K were determined for this complex. The change of N-donor ligand from phen to dmdpy resulted in a pentacoordinated Cu(2+) dimer, however, since the divergent ligand for both families was the same, the small interaction between the copper(II) ions was obtained, as evidenced by EPR and magnetization measurements. The second system presents Ln(3+) ions with Coumarin-3-carboxylic acid as the organic ligand, where two different families were obtained by changing the proportion of Ln ions and ligand. First family 1D CP were obtained with both components with the same proportion. Magnetocaloric studies were conducted for the Gd(3+) and the obtained maximum magnetic entropy value was smaller than the expected value. For the Tb(3+) and Dy(3+) CPs displayed potential as nanomagnets due to the signal obtained in dynamic magnetic measurements. Photoluminescent studies for Eu(3+) and Tb(3+) CPs were conducted, where 0.30 ± 0.05 ms and 0.13 0.05 ms emission lifetime was estimated. The second family obtained had a Ln(3+) and 3-HCCA proportion of 1:3, and resulted in a 1D coordination polymer, where the extension of the polymeric chain had the same mechanism. Photoluminescent studies for Eu(3+) and Tb(3+) CPs were conducted, where an increase in the emission lifetime from 0.30 mais ou menos 0.05 ms to 0.45 0.05 ms for Eu(3+) derivate was observed due to the removal of one H2O molecule coordinated to the europium ion. This work resulted, at the time of this dissertation, in the publication of two scientific papers, as well as a submitted paper that is currently under review.