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Doctoral Thesis
DOI
https://doi.org/10.11606/T.43.1991.tde-02072013-155715
Document
Author
Full name
Elisabeth Andreoli de Oliveira
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 1991
Supervisor
Committee
Figueiredo Neto, Antonio Martins (President)
Bisch, Paulo Mascarello
Mammana, Alaide Pellegrini
Salinas, Silvio Roberto de Azevedo
Santos, Marcus Bastos Lacerda
Title in Portuguese
Estudo de estabilidade química e propriedades de ancoramento em cristais líquidos liotrópicos
Keywords in Portuguese
Ancoramento
Ferrofluido
Liotrópicos
Nemáticos
Abstract in Portuguese
Apresentamos um novo cristal liquido liotrópico, onde o álcool (utilizado nas misturas liotrópicas com fases nemáticas biaxial e uniaxiais), é substituído por um detergente. Essa nova mistura é composta por laurato de potássio, cloreto de decilamônia e água e apresenta fases nemáticas uniaxiais, calamitica e discótica, e biaxial. É apresentada uma superfície do diagrama de fases dessa mistura e são determinados alguns parâmetros microscópicos. Nesse estudo são utilizadas as técnicas de microscopia óptica de luz polarizada, conoscopia e difração de raios x. É feito um estudo comparativo da estabilidade química desse sistema, em relação à mistura com álcool. É feito um estudo sistemático das propriedades de ancoramento de cristais líquidos liotrópicos em superfícies de vidro (lisas e com ranhuras), utilizando a técnica de microscopia óptica de luz polarizada. Um novo fenômeno é observado, o deslizamento do diretor na superfície de contorno. Um modelo qualitativo, é proposto, baseado na existência de urna bicamada anfifílica, com defeitos, na interface. São determinados os tempo de orientação e tempo de relaxação para as amostras e os resultados são comparados às previsões do modelo proposto. Também é apresentado um método de tratamento de superfícies de vidro para orientação de cristais líquidos liotrópicos.
Title in English
Study of chemical stability and properties of anchoring in lyotropic liquid crystals
Keywords in English
Anchoring
ferrofluid
Lyotropic
nematic
Abstract in English
We present a new lyotropic liquid crystal, where the alcohol (used in lyotropic mixtures that present biaxial and uniaxial nematic phases) is substituted by a detergent. This new mixture is composed by potassium laurate, ammonium decylchloride and water and presents uniaxial and biaxial nematic phases. A surface of the phase diagram os this mixture is presented and some microscopical parameters are determined. In this investigation the techniques of polarised optical microscopy, conoscopy and X ray- diffraction are used. The chemical stability of this mixture is compared to the mixture with alcohol. The anchoring properties of lyotropic liquid crystals on glass surfaces (smooth and with grooves) are also investigated, using optical polarising microscopy. A new phenomen is observed, the gliding of the director at the boundary surfaces. A qualitative model is proposed, based on the existence of an anphiphilic bilayer with defects, at the interface. The orientation and relaxation times are determined and compared to the ones predicted by the model. It is also presented, a method for treating glass surfaces with ferrofluid that is applied to orient lyotropic liquid crystal samples.
 
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45887Oliveira.pdf (1.18 Mbytes)
Publishing Date
2013-08-06
 
WARNING: The material described below relates to works resulting from this thesis or dissertation. The contents of these works are the author's responsibility.
  • METTOUT, B., et al. Theory Of The Lamellar-Hexagonal Transformation: Tilted Mesophases In Lyotropic Systems [doi:10.1103/PhysRevE.56.6829]. Physical Review E [online], 1997, vol. 56, p. 6829-6833.
  • OLIVEIRA, E. A., and Neto, A.M.F. Surface Treatment Of Glass With Ferrofluid To Orient Liquid Crystals [doi:10.1016/S0375-9601(99)00440-5]. MAGNITNAJA GIDRODINAMIKA [online], 1990, vol. 4, p. 25-28.
  • LONGA, L., et al. Micellar shape dependence of cholesteric pitch in lyotropic liquid crystals [doi:10.1080/026782900750037248]. Liquid Crystals [online], 2000, vol. 27, p. 1669-1673.
  • OLIVEIRA, E. A., et al. Dry-friction And Critical State In Lyotropic Nematic Liquid Crystals In A Magnetic Field [doi:10.1016/0375-9601(96)00587-7]. Modern Physics Letters A [online], 1996, vol. 222, p. 113-118.
  • OLIVEIRA, E. A., and Neto, A.M.F. Anchoring Properties Of Lyotropic Liquid Crystals Near The Nematic- Isotropic Transition [doi:10.1103/PhysRevE.49.629]. PHYSICAL REVIEW E (STATISTICAL PHYSICS, PLASMAS, FLUIDS AND RELATED INTERDISCIPLINARY TOPICS) [online], 1994, vol. 49, p. 629-635.
  • OLIVEIRA, E. A., BARBERO, G., and Neto, A.M.F. Metastable periodic fréedericksz transition in nematic liquid crystals [doi:10.1103/PhysRevE.54.5830]. Physical Review E. (Cessou em 2000. Cont. 1539-3755 Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics) [online], 1996, vol. 54, p. 5830-5831.
  • OLIVEIRA, E. A., LIEBERT, L., and Neto, A.M.F. A New Soap/Detergent/Water Lyotropic Liquid Crystal With A Biaxial Nematic Phase [doi:10.1080/02678298908045677]. LIQUID CRYSTALS [online], 1989, vol. 5, nº 6, p. 1669-1675.
  • OLIVEIRA, E. A., Neto, A.M.F., and DURAND, G. Gliding anchoring of lyotropic nematic liquid crystals on amorphous glass surfaces [doi:10.1103/PhysRevA.44.R825]. PHYSICAL REVIEW A [online], 1991, vol. 44, p. 825-827.
  • OLIVEIRA, E. A., PHOFINOS, P. J., and Neto, A.M.F. Anchoring properties of a lyotropic, nematic discotic CsPFO/water mixture [doi:10.1080/02678299308027760]. LIQUID CRYSTALS [online], 1993, vol. 14, p. 837-842.
  • OLIVEIRA, M. J., and Neto, A.M.F. Reentrant Isotropic - Nematic Transiton In Lyotropic Liquid Crystals [doi:10.1103/PhysRevA.34.3481]. PHYS. REV. A [online], 1986, vol. 34, nº 4, p. 3481-3482.
  • SANTOS, M. B. L., OLIVEIRA, E. A. DE, and Neto, A.M.F. Rayleigh scattering of a new lyotropic nematic liquid crystal system: crossover of propagative and diffusive behaviour [doi:10.1080/026782900750018654]. Liquid Crystals [online], 2000, vol. 27, p. 1485-1495.
  • Sena, C., et al. Liquid crystalline cellulosic elastomers: free standing anisotropic films under stretching [doi:10.1007/s10570-011-9575-2]. Cellulose (London) [online], 2011, vol. 18, p. 1151-1163.
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