Approach to hydrodynamic equilibrium and its time dependence in the system EHEC/SDS/Water

The properties of the system EHEC/SDS/water in solution show considerable time dependence during several hours after preparation. The paper discusses various reasons for this time dependence. Similar time dependence in polymer solutions has been observed elsewhere. It is found that although the system properties vary, a true equilibrium is finally attained for all compositions. The most pronounced time dependence is shown in a region close to and above the CMC of a pure surfactant solution and for polymer concentrations at least equal to the critical overlap concentration. It is proposed that part of the explanation resides in the fact that in the solution preparation there appears intermediate states corresponding to high local polymer concentrations. Some quantitative aspects of the time dependence are also discussed.