Dielectric and Structural Properties of a Water-Oil Emulsion at the Gel-Microemulsion Transition

Abstract

The dielectric response (1 MHz + 10 GHz) and the structure of a water-oil emulsion were studied as a function of temperature. It was observed that the water component causes the dielectric loss of the emulsion in the crystalline gel phase at low temperatures. However, the dielectric loss decreases discontinuously at the gel-microemulsion transition near 60 "C. At higher temperatures, i.e. in the microemulsion phase of the systems, the dipole relaxation becomes very slow, similar to that of ice. This behaviour is explained by an enhanced connectivity of the hydrogen bonds of water in the micelles of the microemulsion. We conclude that the water in the micelles behaves like frozen water, even at temperatures above 60 "C.

Structural and dielectric properties of synthetic glycolipids in mixtures with water

“…From those chemically pure materials a well-defined phase behavior, i.e., sharp phase transitions can be expected. The methods we used were the classical technique of x-ray diffraction to explore the structural properties and the measurement of the dielectric function at microwave frequencies that we had applied on phospholipid systems (4) and microemulsions (5). 645 [1987/1983]; Bayer AG, Wuppertal, FRG).…”

Critical Dielectric Behavior of Micellar Water below the Cloud point of a Water-Oil Microemulsion

“…This result is in agreement with the model of water being in an icelike state when it is confined by amphophilic molecules in a small volume. 7 In close vicinity of a boundary (within a few molecular distances) the viscosity of water is known to be enhanced like that of butter or toffee and makes the water behave like "soft ice." 9 When two opposite boundaries come close together as they do in lipid-water layer structures, the dynamic properties of this so-called bound water are dominated by the boundary influence.…”

“…The interfacial interaction is even more effective for micelles since there the water is confined in all three dimensions. 7 The percolation model extended to three-dimensional confinement is in favor of this argument. 12 Previous low-frequency studies 3 " 5 yielded the effective dielectric response of the microemulsions due to surface polarization whereas our data obtained at 10 GHz are suitable for comparison with bulk-water data.…”