RHEOOPTICAL STUDY OF WORM-LIKE MICELLES UNDERGOING A SHEAR BANDING FLOW

We report in this letter a rheo-optical study of the non-linear behavi our of a solution of worm-like micelles made of aqueous surfactant sol utions of cetyltrimethylammonium chloride (CTAC) with sodium salicylat e (NaSal) and sodium chloride (NaCl) salts. The theological data show an asymptotic behaviour of the stress with the shear rate. This result is confirmed by the flow birefringence measurements where the birefri ngence intensity and the extinction angle are found to follow the same behaviour. These results, supported by an optical visualization of tw o phases in the plane of flow, corroborate the shear banding flow pred icted by the non-linear theology model.