Abstract
Transient electric birefringence (TEB) studies have been carried out on water-in-oil w/o microemulsions stabilized by Ni(AOT)(2), the nickel salt of bis(ethylhexyl) sulfosuccinate. The system forms rod-shaped droplets at low water contents which convert to more spherical aggregates as the water content is increased. TEB data have been obtained as a function of microemulsion volume fraction, phi, water content, and temperature. Relaxation transients of the electric birefringence signal were found to be nonexponential, following asymptotically a stretched-exponential behavior. The value of the stretching exponent at low volume fraction is consistent with the assumption that the length probability distribution is exponential. A model describing the Kerr response of the microemulsion droplets is developed. By using this model we derive the specific Kerr constant as a function of the volume fraction, finding a good agreement with the experimentally observed behavior. We also use the model to derive, from the initial slope of the relaxation, the mean rod length L-m. It is found that L-m grows approximately as the square root of phi. Values for L-m obtained from TEB are in good agreement with those obtained from small-angle neutron scattering measurements.
| Original language | English |
|---|---|
| Pages (from-to) | 1-7 |
| Number of pages | 7 |
| Journal | Langmuir |
| Volume | 14 |
| Issue number | 1 |
| Publication status | Published - 6 Jan 1998 |