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Doctoral Thesis
DOI
https://doi.org/10.11606/T.46.1999.tde-02122009-142937
Document
Author
Full name
Zósia Angélica de Sant'Ana
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 1999
Supervisor
Committee
Vanin, José Atílio (President)
Arêas, Elizabeth Pinheiro Gomes
El Seoud, Omar A.
Figueiredo Neto, Antonio Martins
Itri, Rosangela
Title in Portuguese
Propriedades reológicas e magnéticas de liomesofases colestéricas uni e biaxiais
Keywords in Portuguese
Colestérico
Cristal líquido
Propriedades magnéticas
Reologia
Transição de fase
Abstract in Portuguese
Neste trabalho, várias técnicas foram utilizadas para estudar mesofases constituídas por laurato de potássio, cloreto de decilamônio, água e sulfato de brucina. Este sistema foi eleito por apresentar a fase colestérica biaxial, cuja caracterização continua se constituindo um problema digno de investigação. Foram efetuadas medidas reológicas sobre sistemas nemáticos e colestéricos, em diferentes composições e condições. Os valores das viscosidades aparentes foram calculados e o comportamento caracterizado. Para os estudos de RMN, introduziu-se nas amostras uma molécula probe, o racêmico dl alanina, procurando-se verificar se havia diferença na interação dos enantiômeros d e I com a matriz colestérica. Os espectros foram obtidos com variação de temperatura. Compararam-se os dados de variação do parâmetro de ordem, obtidos dos acoplamentos diretos, com a semi largura da linha larga dos espectros de próton, para obter informações sobre o comportamento da alanina e das micelas colestéricas. Todas as fases foram acompanhadas por estudos de microscopia sob luz polarizada, técnica simples e eficiente utilizada para caracterizar tipos de fases de cristais líquidos.
Title in English
Rheological and magnetic properties of uni and biaxial cholesteric liomesophases
Keywords in English
Cholesteric
Liquid crystal
Magnetic properties
Phase transition
Rheology
Abstract in English
In this work, several techniques were used to study mesophases constituted by potassium laurate, decylammonium chloride, water and brucine sulfate. This system was chosen for presenting a cholesteric biaxial phase, whose characterization continues to be worthy of investigation. Rheological measurements were made on nematic and cholesteric systems, in different compositions and situations. The values of apparent viscosity were calculated and the behaviour was characterized. For the RMN studies, a probe moIecule, the racemic form of dl alanine, was introduced in the sampIes trying to verify difference between in interaction of the enantiomers d and I with the main cholesteric matrix. The spectra were obtained with temperature variation. It was compared the data of variation of the order parameter, obtained from the direct couplings, with the half width of the wide line of the proton spectra, to obtain information about the behaviour of the alanine and of the cholesteric micelles. All the phases were accompanied by microscopy studies under polarized light, simple and efficient technique to characterize types of liquid crystal phases.
 
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Publishing Date
2009-12-03
 
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