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Dipolar and quadrupolar couplings measured from NMR experiments, and order parameters obtained from these couplings, are reported for a number of small solutes dissolved in several nematic liquid crystals. These results are discussed in terms of the solute-solvent interactions. It has been shown that the interaction between the solute molecular quadrupole moment and a mean external electric field gradient due to the liquid crystal accounts for most but not all of the ordering of molecular hydrogen. The remaining contribution to ordering is discussed in terms of possible mechanisms. The anisotropic couplings observed for methane and acetylene are discussed in terms of a model which takes into account the interaction between the vibrations and rotations of the solute. Excellent agreement between the observed and calculated dipolar couplings is obtained. Evidence is given that these two solutes experience the same field gradient as molecular hydrogen. In a mixture of 55wt per cent 1132 (Merck ZLI 1132) and 45wt per cent EBBA (N-(4-ethoxybenzylidene)-4'-n-butylaniline at 301.4K the deuterons in D₂ experience no external electric field gradient. The order parameters of a series of solutes in this mixture are calculated in terms of a simple model for the short range interactions which depend on the size and shape of the solute. These calculated order parameters are in very good agreement with the experimental results. In liquid crystals where the field gradient is not zero it is shown that the combination of the short range interaction model and the electric field gradient - molecular quadrupole moment mechanism predicts the order parameters very well. / Science, Faculty of / Chemistry, Department of / Graduate

Orientador: Celso Aparecido Bertran / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-22T10:56:23Z (GMT). No. of bitstreams: 1 Campos_DaniellaDiasPalombinode_D.pdf: 44951379 bytes, checksum: 1a18d9ffcb14751022a3de58b577f652 (MD5) Previous issue date: 2012 / Resumo: Sistemas auto-organizados, preparados com surfactantes nonilfenil etoxilados com diferentes tamanhos de cadeia etoxilada, foram utilizados para sintetizar nanopartículas de hidroxiapatita (HAP - Ca5(PO4)3OH), que é o fosfato de cálcio majoritariamente presente nos tecidos mineralizados dos vertebrados. O efeito do tamanho do grupo etoxilado do surfactante foi avaliado tanto na formação dos sistemas auto-organizados quanto nas propriedades das partículas de HAP precipitadas in situ nestes sistemas. Cristais líquidos hexagonal reverso, lamelar, hexagonal e cúbicos foram formados, nesta ordem, a medida que surfactantes com maiores grupos etoxilados foram empregados. Os fosfatos de cálcio sintetizados em todos os sistemas auto-organizados apresentaram-se na forma de nanohastes, de modo que as nanohastes formadas nas fases anisotrópicas (cristais líquidos hexagonais e lamelares) apresentaram diâmetros mais uniformes quando comparadas àquelas sintetizadas nos sistemas auto-organizados isotrópicos. O diâmetro das hastes de HAP comparado com as dimensões dos sistemas auto-organizados sugere que estas se formaram pela aglomeração orientada de partículas ainda menores de HAP, o que foi evidenciado por microscopia eletrônica de varredura (SEM-FEG). Estes resultados, em conjunto com medidas de tempo de relaxação transversal (T2) do hidrogênio das moléculas de água presentes nos sistemas auto-organizados, permitem propor que a limitação do tamanho das nanopartículas de HAP seja conseqüência da limitação da difusão iônica in situ e que a morfologia de hastes é resultante da autoorganização das fases. / Abstract: Self-assembled systems from nonylphenol ethoxylate surfactants were prepared using surfactants with different hydrophilic chain lengths. These systems were used to synthesize hydroxyapatite (HAP - Ca5(PO4)3OH) nanoparticles, the main constituent of vertebrates mineralized tissues. The surfactant hydrophilic length influence was evaluated both on the self-assembled systems formation and on the properties of HAP nanoparticles which were obtained by in situ precipitation in these systems. As the surfactant hydrophilic length increased different liquid crystals were formed in this sequence: reverse hexagonal, lamellar, normal hexagonal and cubic mesophases. HAP nanoparticles synthesized in all selfassembled systems had morphology of rods. Particles precipitated in the anisotropic systems (hexagonal and lamellar liquid crystals) had more uniform diameters compared to particles precipitated in the isotropic systems (cubic liquid crystals). The HAP nanorods diameters were bigger than the repetition distances of the self-assembled systems. This occurrence, evidenced by SEM-FEG micrographs of the HAP nanoparticles, suggests that the nanorods were formed by even smaller HAP particles which were previously confined in the hydrophilic domains of the phases, and after the surfactant removal they were neatly clustered as induced by the self-assembled systems. These results along with the transversal relaxation times measurements (T2) for hydrogen in water molecules belonging self-assembled systems, allow us to propose the following: there is a reduced ionic diffusion within the liquid crystals hydrophilic domains and it is the cause for the size particles limitation and the particles morphology is influenced by the self-assembling of the systems. / Doutorado / Físico-Química / Doutora em Ciências

Orientador: Elisa Maria Aparecida Giro / Resumo: A clorexidina destaca-se por sua eficácia no combate à diversos micro-organismos de interesse cariogênico. No entanto, sua forma de utilização mais conhecida é o enxaguatório bucal, que não possui aplicação universal para pacientes com necessidades especiais. Desse modo, um desafio para a indústria farmacêutica é o desenvolvimento de um sistema para substituir os enxaguatórios bucais. O objetivo desse estudo foi incorporar digluconato de clorexidina, óleo essencial de Cymbopogon citratus ou a associação dessas substâncias a um sistema precursor de cristal líquido mucoadesivo, realizar a caracterização físico-química desse sistema e avaliar in vitro seu potencial antimicrobiano em biofilmes polimicrobianos. As formulações foram caracterizadas por meio de microscopia de luz polarizada, análises reológicas, mucoadesão e perfil de liberação. Posteriormente, foi avaliada a capacidade de redução da acidogenicidade, composição microbiana e dosagem de polissacarídeos extracelulares insolúveis em água dos biofilmes formados a partir da saliva de um doador. Os dados da seleção do doador de saliva, dos testes de CIM e CBM do óleo essencial de C. citratus e do digluconato de clorexidina, as análises reológicas do sistema e o perfil de liberação in vitro foram analisados descritivamente. Enquanto, para os testes de mucoadesão, contagem de micro-organismos do biofilme, pH, peso seco dos biofilmes e dosagem de polissacarídeos extracelulares insolúveis em água, dependendo da normalidade e ho... (Resumo completo, clicar acesso eletrônico abaixo) / Mestre

In this work, we develop an effective field theory program for many-body systems out of finite temperature equilibrium. Building on recent work, we combine powerful mathematical tools such as the Schwinger-Keldysh closed-time-path formalism, the coset construction, and Wilsonian effective field theory to construct novel actions that describe a wide range of many-body systems out of finite-temperature equilibrium. Unlike ordinary actions, these non-equilibrium actions account for dissipation and statistical and quantum fluctuations. The novel actions constructed include those for solids, supersolids, nematic liquid crystals, smectic liquid crystals in phases A, B, and C, chemically reacting fluids, quasicrystals, higher-form dual theories of superfluids and solids, and plasmas that can support large charge density. In order to construct these actions, we propose a new kind of coset construction with a total of four distinct types of inverse Higgs constraints. We extend the coset construction to account for higher-form symmetries and investigate the relationship between two kinds of ’t Hooft anomalies and spontaneous symmetry breaking.

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Squaraine dyes have been a subject of extensive investigations lately due to their wide applications in important technological fields such as bioimaging probes, bioconjucation, second generation photosensitizers for photodynamic therapy, second harmonic generating organic dyes, two-photon absorbing materials with large cross section values, and, finally, photoconducting materials in photovoltaic cells. While a large number of patents and papers has been produced regarding their applications limited work has been done concerning their thermotropic behavior, including their liquid crystalline properties, or correlation of the crystalline structure to both the solid state aggregation and their photophysical properties. In the first chapter of this dissertation, a series of squaraine dyes, based on 2, 4-(4-(N,N-di-n-alkylamino)-2-hydroxyphenyl)squaraine including ethyl, propyl, butyl, pentyl, hexyl, and heptyl derivatives, were synthesized by condensation of the corresponding 4-(N,N-di-n-alkylamino)-2-hydroxyphenol with squaric acid. The thermal behavior of the series was recorded using both thermogravemetic analysis (TGA) and differential scanning calorimetry (DSC) while their crystalline structures were elucidated via single crystal X-ray diffraction. The length of the alkyl chain proved to have a significant effect on both the thermotropic behavior and the crystalline structure of the squaraine series. Two derivatives, butyl and heptyl, revealed the presence of liquid crystalline mesophases, smectic and nematic, respectively, that were confirmed and characterized via polarized light microscopy (PLM) and X-ray diffraction. In the second chapter, J- and H- aggregates were investigated in thin films by UV-vis spectroscopy; several of the derivatives formed H- and/or J-aggregates upon thin film formation via spin coating before and after thermal annealing, as indicated by UV-vis spectroscopy. The molecular structure, crystal structure, aggregation, and thermal behavior provide insight into the supramolecular assembly of this important class of materials. Photophysical measurements revealed large molar absorptivity, reasonably high fluorescence quantum yields, and significant fluorescence anisotropy, making these derivatives suitable candidates for a number of electro-optic and photonics applications. The third chapter was devoted to investigate liquid crystal-directed supramolecular assembly of a squaraine dye. Thus, The squaraine (SQ) dye, 2, 4-bis (4-(N,N-di-n-hexylamino)-2-hydroxyphenyl)squaraine was used to prepare a series of SQ dye/cholesteryl pelargonate mixtures with varying dye concentrations (1%, 3%, 7.5%, 10.8%, 15%, and 20% w/w). Their phase transitions were investigated using differential scanning calorimetry, polarized light microscopy and X-ray diffraction. The squaraine dye itself exhibits no liquid crystalline behavior. The concentration of the dye in the cholesteric compound proved to have a significant effect on the dye aggregation behavior and phase transitions in cholesteryl pelargonate manifested by the appearance of new mesophases and formation of J- and H- aggregates. The texture morphology, X-ray diffraction analyses, and UV-vis absorbance spectra provide compelling evidence of the viability of the self-assembly of squaraines in the liquid crystalline mesophase. In the last chapter we will discuss possible modifications that can improve the aggregation systems.