Dielectric Properties of Nonionic Microemulsions

T. M. Usacheva, N. V. Lifanova, and V. I. Zhuravlev

Department of Chemistry, Vorob’evy gory, Moscow State University, Moscow, 119899 Russia

Received February 7, 1996

Abstract—The static permittivity, conductivity, and density of single-phase isotropic microemulsions contain-
ing Brij-97, n-butanol, dodecane, and water were measured at 20°C. The data on the static permittivity were
analyzed using two models considering the microemulsions as disperse systems containing (I) spherical parti-
cles or (II) anisotropic ellipsoids of revolution. Models I and II demonstrate that the reversal of the w/o micro-
emulsion takes place at a water content between 20 and 30 wt %. According to model II, the dispersed particles
in the w/o microemulsions are disc-shaped. When the water concentration in the o/w microemulsions rises, the
axis length ratio for the oblate ellipsoids of revolution increases. At a water content of 70 wt %, the oblate ellip-
soids transform into prolate ones with an almost spherical shape. Flocculation of several spherical particles at
a low water content may be one of possible causes of the formation of ellipsoidal particles.

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