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Shear-induced textural transitions in flow-aligning liquid crystal polymers.
1Department of Chemical Engineering, McGill University, 3610 University Street, Montreal, Quebec, Canada H3A 2B2.
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
|February 3, 2004
Summary
Sheared nematic polymers transform textures via defect lattices and gases as shear rate increases. These transitions, controlled by Ericksen (Er) and Deborah (De) numbers, mirror experimental observations in lyotropic polymers.
Area of Science:
- Polymer Science
- Rheology
- Soft Matter Physics
Background:
- Nematic polymers exhibit complex textural transformations under shear.
- Understanding these transformations is crucial for predicting material behavior.
Purpose of the Study:
- To model and understand textural changes in sheared thermotropic nematic polymers.
- To identify key parameters governing texture formation and evolution.
Main Methods:
- Formulation and solution of nematodynamics equations.
- Analytical, scaling, and numerical characterization of solutions.
- Modeling texture transitions as a function of shear rate.
Main Results:
- Texture formation is controlled by Ericksen (Er) and Deborah (De) numbers.
- A transition cascade occurs: unoriented monodomain → defect lattice → defect gas → oriented monodomain.
- Texture vanishes at high shear rates (De > 2) as coarsening dominates.
Conclusions:
- The model accurately predicts textural transitions observed in sheared lyotropic nematic polymers.
- Ericksen and Deborah numbers are critical for controlling texture evolution.
- The study provides a framework for understanding shear-induced microstructural changes in nematic polymers.