Light Scattering Experiments on Shear Induced Structures of Micellar Solutions

The formation of shear induced structures (SIS) of a mixed micellar solution of tetradecyldimethylaminoxide and sodium dodecylsulfate is studied by light scattering experiments under shear (rheo-optical method). In the shear rate- as well as in the time-dependent measurements we found an aggregation process taking part in the SIS formation. Below the critical shear rate for the occurrence of SIS, the shear rate dependent experiments show an increased scattering intensity, indicating micellar associates. Above the critical shear rate, we found structures oriented in the direction of flow. The time dependent measurements show that the SIS formation can be regarded as a process which can be divided into three stages: induction-aggregation-orientation. After the aggregation, we found a temporal process in which the orientation increases to reach complete orientation in the direction of flow.