Materials Science Forum, Vol.509, 177-186, 2006
Time-dependent rheological behavior of liquid crystalline dispersions
The rheological response of Aerosol OT (AOT)/water liquid crystalline dispersions is reported here using shear flows. The dispersions exhibit an apparent yield stress and strong non-Newtonian behavior. Steady state and pre-shear dynamical experiments reveal shear-induced structural changes. Under increasing-and-decreasing shear stress experiments, the dispersions exhibit anti-thixotropic hysteresis loops. Once a critical stress is surpassed, an additional thixotropic loop is observed at high shear stress levels. This inverse loop at high shear stresses depends on the previous shear history and on both the rate of change and the maximum attained value of shear stress. The number density of the globular structures in the sheared sample is larger than in one non-sheared sample, but their sizes are smaller than those of the non-sheared sample.