By means of ultrasonic and Brillouin light-scattering techniques, we have performed extensive measurements of the attenuation coefficient and sound velocity in 2-butoxyethanol aqueous solutions over a large temperature range. In the more concentrated solutions, the frequency dependence of these properties is well accounted for by a double relaxation time equation thus excluding contributions from concentration fluctuations. This finding, as well as the overall behavior as a function of concentration and temperature, suggests the presence of alcohol aggregates beyond a characteristic concentration-temperature line resembling a critical micelle concentration curve in micellar systems. The similarity between the ultrasonic behavior and the type observed in nonionic surfactant aqueous solutions, as well as indications from other experimental sources, strongly supports the possibility that butoxyethanol aggregates are micellelike structures.

• Received 11 March 1991

DOI:https://doi.org/10.1103/PhysRevA.44.2578