Shear-Induced Texture Changes in Cholesteric Liquid-Crystal Mixtures

Rheological studies on a 23/77 wt% cholesteryl chloride-cholesteryl oleyl carbonate liquid-crystal system show isothermal shear-induced texture changes. The shear-induced textures show non-Newtonian behavior at shear rates below {~} 5 sec^-1 and Newtonian behavior above this value. These textures have been optically characterized as the Grandjean and focal conic. At shear rates in excess of {~} 1000 sec^-1, non-Newtonian behavior is observed and identified with the homeotropic texture. The first normal-force measurements on a liquid-crystal system are reported.