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Master's Dissertation
DOI
https://doi.org/10.11606/D.43.1998.tde-16072021-140515
Document
Author
Full name
Leila Thomazelli Thieghi
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 1998
Supervisor
Committee
Figueiredo Neto, Antonio Martins (President)
Castro, Tania Tome Martins de
Oliveira Junior, Osvaldo Novais de
Title in Portuguese
Comportamento crítico não-universal na transição de fases nemática uniaxial-biaxial em uma mistura liotrópica
Keywords in Portuguese
CRISTAIS LÍQUIDOS
MATÉRIA CONDENSADA
Abstract in Portuguese
Realizamos medidas do expoente crítico do parâmetro de ordem, ´BETA´, ao longo da transição de fase nemática uniaxial-biaxial em um cristal líquido liotrópico composto por laurato de potássio/1-decanol/água, em fuåção da concentração relativa dos componentes da mistura. Para a determinação do expoente crítico ´BETA´ medimos a birrefringência do cristal líquido em função da temperatura, durante a transição de fases. As medidas foram realizadas através da técnica de microscopia óptica de luz polarizada com compensador de Berek. Os resultados obtidos mostram que o expoente crítico do parâmetro de ordem, ´BETA´, não segue nem o Modelo XY nem o Modelo de Campo Médio, podendo ter valores entre 1/3 e 1, tendo uma forte dependência com a composição da amostra
Title in English
Non-universal critical behavior in uniaxial-biaxial nematic phase transition in a lyotropic mixture
Keywords in English
CONDENSED MATTER
LIQUID CRYSTALS
Abstract in English
Measurements were made of the critical exponent of the order parameter 'BETA' along the phase transition nematic uniaxial-biaxial in a lyotropic liquid crystal composed by potassium laurate/1-decanol/water, as a function of the relative concentration of the mixture components. For the determination of the critical exponent 'BETA' we measured the birefringence of the liquid crystal as a function of the temperature, along the phase transition. The measurements were done using optical microscopy with a Berek compensator. The results show that the critical exponent of the order parameter 'BETA' follows neither the XY Model nor the Mean Field Model, presenting values between 1/3 and 1, strongly dependent on the sample composition.
 
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1998Thieghi.pdf (66.61 Mbytes)
Publishing Date
2021-08-31
 
WARNING: The material described below relates to works resulting from this thesis or dissertation. The contents of these works are the author's responsibility.
  • THIEGHI, L. T., et al. Nonuniversal critical behaviour at the uniaxial-biaxial nematic phase transition in a lyotropic mixture [doi:10.1103/PhysRevLett.80.3093]. Physical Review Letters [online], 1998, vol. 80, nº 14, p. 3093-3096.
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