The orientation process of cholesteric lyotropic liquid crystals submittedto shear

The rheological behavior of cholesteric lyotropic liquid crystals can give information about the chiral forces involved on the formation of the choles teric arrangement. In the present work, it was studied the effect of these forces on the orientation process of a liquid crystal system submitted to a period of shear. It was prepared different mesophases based on decylammoni um chloride with different amounts of cholesterol added as inductor. The ob tained results showed that the cholesteric system acquires an initial arran gement pseudoplastic that turns to a newtonian as function of the rest time or the shear time. The orientation process should involve an initial step of destruction of a pre-existent cholesteric structure caused by shear that leading to the formation of microdomains with different orientations. In a second stage these microdomains will be orientated either by a shear proce ss or by the performance of the elastic constants forming the final structu re that is quite similar to the nematic one. (C) 2001 Elsevier Science B.V. All rights reserved.