DIELECTRIC-PROPERTIES OF NONIONIC MICROEMULSIONS

The static permittivity, conductivity, and density of single-phase iso tropic microemulsions containing Brij-97, n-butanol, dodecane, and wat er were measured at 20 degrees C. The data on the static permittivity were analyzed using two models considering the microemulsions as dispe rse systems containing (I) spherical particles or (II) anisotropic ell ipsoids of revolution. Models I and II demonstrate that the reversal o f the w/o microemulsion takes place at a water content between 20 and 30 wt %. According to model II, the dispersed particles in the w/o mic roemulsions are disc-shaped. When the water concentration in the o/w m icroemulsions rises, the axis length ratio for the oblate ellipsoids o f revolution increases. At a water content of 70 wt %, the oblate elli psoids transform into prolate ones with an almost spherical shape. Flo cculation of several spherical particles at a low water content may be one of possible causes of the formation of ellipsoidal particles.