THEORY AND SIMULATION OF OPTICAL BANDED TEXTURES OF NEMATIC POLYMERS DURING SHEAR-FLOW

Simulations of banded texture optical phenomena during shearing of liq uid crystalline polymers are presented. A computational analysis of th e polarized light transmission pattern for the nonhomogeneous orientat ion structure of a representative nematic polymer during shear start-u p flow is presented. Simulations show that the shear-induced structure that gives rise to the banded texture is an array of tubular orientat ion inversion walls whose axes are normal to the flow direction. The c orresponding optical computations are in good agreement with the exper imentally observed banded textures of light transmission under crossed polars of sheared poly(gamma-benzyl-L-glutamate) (PBLG) (Yan, N. X.; Labes, M. M. Macromolecules 1994, 27, 7843). The computer simulations show the intimate relation between the light transmission pattern and the tubular orientation inversion wall array and, hence, shed a new li ght on the origin of this ubiquitous phenomenon.