Dynamic light scattering of an ionic SDS micellar solution under an AC electric field

The phase separation behavior of near-critical ionic sodium-dodecyl-sulfate (SDS) micellar solution under a sinusoidal electric field was investigated by phase-contrast optical microscopy and by the small-angle dynamic light scattering method. The sinusoidal electric field significantly deformed the concentration domains and shifted the phase separation temperature. The au tocorrelation function under a sinusoidal electric field was measured in th e vicinity of a phase separation temperature range of 0.10 K < T-p - T < 0. 97 K, where T-p - T is the temperature distance from the phase separation t emperature in quiescent state T-p. The correlation function with an oscilla tory part in the longer correlation time region was observed. The occurrenc e of the oscillatory mode, which depended on both the applied field frequen cy and the ambient temperature, indicates deformation of concentration fluc tuation domains by dynamical coupling between the phase separation and the applied sinusoidal electric field.