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CHAPTER 2
Rheological Theory and Simulation of
Surfactant Nematic Liquid Crystals
ALEJANDRO D. REY and E. E. HERRERA-VALENCIA
Department of Chemical Engineering, McGill University, Montréal, Quebec, Canada
Abstract
This chapter presents a comprehensive review of rheological theory, modeling, and
simulation of surfactant nematic liquid crystalline phases, including calamitic and dis-
cotic micellar solutions and wormlike micelles. A review of verifi able rheological liquid
crystal models for lyotropic nematics highlighting the mechanisms that control orienta-
tion behavior under shear, anisotropic viscoelasticity, and non-Newtonian behavior.
Since defects and textures are essential characteristics of these materials that affect the
fl ow properties, an in-depth review of physical and rheophysical defects is presented,
including defect nucleation and coarsening processes. The theory for micellar nematics
is applied to textures, fl ow birefringence, phase transition under shear, orientation
fl uctuations, and fl ow alignment, and the predictions are compared with experimental
data. The theory is fi nally applied to transient shear fl ows of wormlike micellar nematic
solutions, and the predicted banded textures and transient stress responses are com-
pared to rheological experiments. The predictions provide a new way to extract addi-
tional information from experimental rheological data and allow to distinguish the role
of liquid crystalline properties such as viscoelastic anisotropy, fl ow alignment, coupling
between orientation kinematics, and fl ow kinematics. The rheological predictions show
a strong similarity with other nematic materials, including low-molar-mass thermo-
tropes and lyotropic nematic polymers.
2.1
Introduction
22
2.1.1
Lyotropic Liquid Crystals
22
2.1.2
Micellar Nematic Liquid Crystals
23
2.1.3
Wormlike Nematic Solutions
25
2.1.4
Diamagnetic Anisotropy
27
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