Flow birefringence experiments showing a shear-banding structure in a CTAB solution

Experiments of flow birefringence have been performed on a concentrated solution of CTAB submitted to shear in a Couette cell. Qualitative observations of the flow in the annular gap of the Couette device let us clearly see that the flow is divided into two layers when the shear rate exceeds a critical value. This shear banding structure is shown on a set of photographs. The extinction angle and the retardation were measured as a function of the shear rate for different temperatures. The results are in agreement with the predictions of the shear banding theory.