RHEOLOGY OF LYOTROPIC LIQUID-CRYSTALS OF AEROSOL OT .1. LOW CONCENTRATION REGIME

The rheological behavior of AOT/water dispersions over the whole two-phase concentration range (1.4 to 18.5 ± 1 wt% AOT at 25°C) is reported here. At a concentration around 8 wt% AOT, the dispersions undergo a phase inversion from being water-continuous to being liquid crystalline-continuous. Below the phase inversion point the water-continuous dispersions are viscoelastic. At the phase inversion point there is a substantial reduction in viscosity and in relaxation times. Above the phase inversion point, the dispersions become more elastic and show increasing values of viscosity and relaxation time. Shear viscosities of water-continuous dispersions exhibit hysteresis in increasing-decreasing shear rate experiments. A shear thickening region was detected in the increasing shear mode, which may be associated with the formation of shear-induced structures similar to those found above the phase inversion point. © 1993 Academic Press, Inc.