Degree Name

Master of Science (MS)

Semester of Degree Completion

1986

Thesis Director

David W. Ebdon

Abstract

A surfactant selective electrode using a PVC membrane was constructed. A surfactant (sodium dodecylbenzene-sulfonate)-H2O system was studied at 15°, 19°, 25°, and 40°C with the PVC electrodes, a Na+ selective electrode, and a conductivity bridge. Pre-micelle regions at the above temparatures were observed. The critical micelle concentrations (CMCb) obtained by the PVC electrodes in salt-free systems are: 1.63x10-3 M at 15°C, 1.48x10-3 M at 19.1°C, 1.52x10-3 M at 25°C, and 1.73x10-3 M at 41.6°C. The CMC'c obtained by the Na+ electrode are: 1.62x10-3 M at 15°C, 1.37x10-3 M at 19.3°C, 1.47x10-3 M at 25°C, and 1.98x10-3 M at 40.5°c. The CMC obtained by the conductivity measurement is: 1.62x10-3 M at 25°C. The counterion binding was calculated and it was found that it is not constant. An equation, log[DBS-] = constant - rlog[Na+], was obtained. The r value was calculated mathematically and it was found that it is related only to the slopes of the plots of EMF vs log [NaDBS] obtained by the PVC electrode and the Na+ electrode. Hence the equality of r and the counterion binding proposed by the charged phase separation model is questionable. A decrease of the CMC by the addition of salts (NaNO3 and NaCl) was observed with the PVC electrodes. The surfactant system with Cu2+ and Na+ present was also investigated by the PVC electrodes and by a Cu2+ electrode. Complexation between Cu2+ and the micelles was observed and the solubility product of Cu(DBS)2 was calculated to be about 5x10-10.

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