Rheology of the lamellar liquid-crystalline phase in polyethoxylated alcohol/water/heptane systems.

Authors

  • F. Cordobés Departamento de Ingeniería Química. Facultad de Química. Universidad de Sevilla
  • J. M. Franco Departamento de Ingeniería Química. Facultad de Ciencias Experimentales. Universidad de Huelva
  • C. Gallegos Departamento de Ingeniería Química. Facultad de Ciencias Experimentales. Universidad de Huelva

DOI:

https://doi.org/10.3989/gya.2005.v56.i2.116

Keywords:

Lamellar mesophase, Liquid crystal, Rheology, Viscoelasticity, Viscosity

Abstract


Linear viscoelastic tests as well as transient and steady flow experiments were carried out on lamellar liquid crystalline samples of poly (oxyethylene) alcohol/water/heptane systems. The effect of surfactant and heptane concentrations on the rheological properties of the lamellar mesophase was investigated. The mechanical spectrum inside the linear viscoelastic regime shows, in all cases, a well-developed plateau region in the whole frequency range studied. The values of the dynamic functions were higher for intermediate surfactant or heptane concentrations indicative of a major development of the elastic network in the midrange of existence of the lamellar phase. Transient and steady flow experiments point out a shear-induced evolution of the lamellar microstructure. Different power law regions with different values of the flow index were detected in the viscosity versus shear rate plots. These shear-induced structural modifications were confirmed by using polarizing microscopy in an optical shearing cell. Structural modifications appear to be highly influenced by shear rate. In general, applying relatively high constant shear rates, the alignment of the bilayers followed by the appearance of the “oily streaks” structure was observed. Appearance of shear-induced vesicles occurs at high heptane content, as indicates the texture of close-packed monodisperse spherulites detected by polarizing microscopy.

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Published

2005-06-30

How to Cite

1.
Cordobés F, Franco JM, Gallegos C. Rheology of the lamellar liquid-crystalline phase in polyethoxylated alcohol/water/heptane systems. grasasaceites [Internet]. 2005Jun.30 [cited 2021Dec.9];56(2):96-105. Available from: https://grasasyaceites.revistas.csic.es/index.php/grasasyaceites/article/view/116

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Section

Research

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