In situ structural investigations of the Synperonic(A7)-water system under shear

摘要

A sample holder was constructed for small-angle X-ray scattering(SAXS) measurements that can be used as a shear cell. The lamellar structure of a nonionic surfactant (Synperonic A7)-water system was investigated in this cell. The SAXS curves of the sample were detected in the steady state and under shear for a certain time, and finally in the steady state once again. The Bragg profiles of the SAXS curves shift to smaller characteristic periodic distances under the shear stress. After shear the Bragg profiles do not return to the starting position but drastic changes can be detected in their shapes which indicate significant changes in the lamellar arrangements. These structural changes also explain the tixotropic behaviour of the system which was observed in rheological tests.