Abstract
AbstractUltrasonic relaxation measurements covering the frequency range 5–100 MHz have been carried out in the isotropic as well as the hexagonal and lamellar liquid crystalline phases of aqueous solutions of the surfactants: caesium perfluorooctanoate, mono‐olein, mono‐caprylin, tetraethylene glycol dodecyl ether (CE04), pentaethylene glycol dodecyl ether (CEO) and di‐(2‐ethylhexyl) sodium sulfosuccinate (aerosol OT). The absorption data obtained in concentrated isotropic solution and also the hexagonal and lamellar phases can be fitted into an equation involving a single relaxation time in the frequency range 25–100 MHz. The concentration and temperature dependence of the relaxation times and amplitudes have been determined. A discussion of the likely mechanisms causing the relaxation will be given. These measurements also show that there is a pronounced increase in the quantity as the different phase boundaries are approached. This is very close to the behaviour of absorption data near the critical point in liquid mixtures.
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