Multiscale simulation of flow-induced texture formation in polymer liquid crystals and carbonaceous mesophases

Abstract

This paper presents theory and simulation of flow-induced structures in liquid crystalline materials, useful to the creation of synthetic material structures and to the biomimetics of natural fibers. A multiscale theory and simulation of hydrodynamic texture formation is presented; it provides fundamental principles for control and optimization of structures in liquid crystal polymers and carbonaceous mesophases. In thermotropic flow-aligning nematic polymers it is found that as the shear-rate increases, the pathway between an oriented non-planar state and an oriented planar state is through meso-texture formation and coarsening, with temperature and shear rate being efficient fields to control the grain size of the texture. For capillary flow of carbonaceous mesophases, the simulations predict the emergence of macroscopic ring patterns whose thickness and density can be controlled by the applied pressure drops. The results provide insight on microstructure formation and control in liquid crystalline materials.

Keywords:

• Liquid crystal polymers
• Carbonaceous mesophases
• Shear flow
• Capillary flow
• Texture
• Disclinations

Acknowledgements

This work was supported primarily by the ERC Program of the National Science Foundation under Award Number EEC-9731680. DG and LRPdAL also gratefully acknowledge the support of Natural Sciences and Engineering Research Council of Canada, and the Eugenie Ulmer Lamothe Fund of the Department of Chemical Engineering at McGill University.