DIRECT OBSERVATION OF SHEAR-INDUCED STRUCTURES IN WORMLIKE MICELLAR SOLUTIONS BY FREEZE-FRACTURE ELECTRON-MICROSCOPY

We report the first direct observation of shear-induced structures in low concentration wormlike micellar solutions. The structures consist of micron-sized patches which are much larger than individual equilibr ium micelles and occupy 5%-10% of the fracture area. Such morphologies are consistent with recent reports of increased light scattering unde r shear how. The structures have a stippled or spongelike texture and contain more surfactant than the background micellar solution. These p atches form aggregates spanning hundreds of microns and are consistent with the shear thickening observed in these systems.