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Abstract:
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O principal objetivo das pesquisas realizadas e apresentadas neste trabalho esta concentrada nos efeitos da adicao de sais eletroliticos monovalentes fortes, como o cloreto de amonio (NH4Cl) e o cloreto de potassio (KCl), na formação de novas estruturas com propriedades liquido-cristalinas ou mudanças drasticas nas estruturas micelares pré-existentes, nas fases micelares isotropica, nematica e lamelar presentes no sistema binario contendo o surfactante amonio entadeca°uorooctanoato e agua (APFO / H2O). Inves-tigamos tambem, a in°u^encia que os sais NH4Cl e KCl produziram na forma e no tamanho dos agregados micelares, bem como sua dependencia com a temperatura. Diversas tecnicas experimentais, como microscopia optica, refratometria de ABBE, tramitancia de luz, difraçao por raios X e etc, foram usadas e dos resultados destas medidas, suas temperaturas de transicoes de fases foram determinadas e uma nova estrutura, formada espontaneamente na solucao e denominada "vesiculas", foi identicada, isto e, estas vesiculas aparecem simplesmente pelo efeito do sal adicionado. Estudos teoricos usando campo medio (Maier-Saupe) em combinaçao, com resultados experimentais foram realizados e o comportamento do paramentro de ordem orientacional micelar com a temperatura, foram obtidas para varias amostras. The main aim of the research performed and presented in this work is concentrated in the e®ects of the addition of strongs monovalents electrolytic salts, as the ammonium chloride (NH4Cl) and the potassium chloride (KCl), in the formation of new structures with liquid-crystallines properties or drastic changes in pre-existing micellar structures in the isotropic, nematic and lamellar phases present in the binary system containing the surfactant pentadeca°uorooctanoate and water (APFO / H2O). We also investigated the in°uence that the salts (NH4Cl and KCl) had on the size and shape of the micellar aggregates as well as their dependency on temperature. Several experimental techniques such as polarizing optical microscopy, direct bulk solution observation, Abbe refractometry, laser light transmission and small angle X ray di®raction were used and from results of these measurements, phase transitions temperatures were determined and, a new structure, formed spontaneously in the solution and named "vesicles", was identi¯ed, i.e., these vesicles appear in the solution simply by the e®ect of the added salt. Theoretical studies using mean ¯eld approximation (Maier-Saupe) in combination with experimentals data were performed and the behavior of the micellar orientational order parameter on temperature, for several samples, obtained. |
