Diffusion Measurements in Microemulsions.
Final rept. Sep 82-Dec 83,
ARMY ARMAMENT RESEARCH AND DEVELOPMENT COMMAND ABERDEEN PROVING GROUND MD CHEMICAL SYSTEMS LAB
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Diffusion coefficient measurements in both aqueous micelles and microemulsions have been carried out using the techniques of polarography and quasielastic light scattering QLS. The former method involves the determination of the diffusion coefficient of an electroactive oil soluble probe at a polarizable microelectrode. For high water content microemulsions, both methods yield the same diffusion coefficients which can be identified as the self diffusion coefficient. For cetyltrimethylammonium bromide CTAB micelles, both methods yield the same result at the salt NaBr concentration at which the QLS measurements are independent of CTAB concentration. In more concentrated microemulsions, QLS data gave diffusion coefficients, in agreement with polarography only for a sodium cetyl sulfate SCS system at 65-75 wt water. For the SCS microemulsions at 60 water, and CTAB microemulsion at 60-75 water, the QLS data yielded rapid, nonexponential decays. However, consistent polarographic diffusion coefficients could still be obtained. By using probes of varying chain length oil solubility, it has been demonstrated that these CTAB and SCS microemulsions containing butanol and pentanol cosurfactants respectively, are not cosolubilized systems but do contain distinct hydrophilic and hydrophobic regions. Author
- Physical Chemistry