Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)



First Advisor

Robert V. Nauman


The surface tension and solubilizations of a number of surfactant solutions were measured in the hope of gaining additional understanding of the structure of micelles. A number of compounds were added to micellar solutions of tetradecyltrimethylammonium bromide. These additives had structural characteristics that were similar to the structure of the cationic head group of the surfactant monomers. The additives were the quaternary ammonium halides; tetramethylammonium bromide, tetraethylammonium bromide, and tetrapropylammonium bromide, and the zwitterionic compounds; glycine, sarcosine, N,N, dimethyl glycine, and betaine. This project was initiated to ascertain whether these particular additives would actually enter the micelles and by so doing, alter the properties of the micellar solutions. The solubilizing powers and surface tensions of the solutions were measured in order to test this hypothesis. An isopiestic procedure was designed so that direct surface tension measurements could be taken. A pychnometric method was also developed to measure the concentrations of the surfactant solutions. Benzene was chosen as the solubilizate for the solubilization experiments. The spectra of benzene in all of the micellar solutions was determined. The concentration of micellar, or solubilized, benzene was calculated by subtracting the concentration of benzene in the aqueous phase. Solutions which had the same concentrations of tetraalkylammonium halide or sodium bromide had virtually identical surface tensions. The solubilizing powers of the tetraalkylammonium halide solutions were essentially the same as that of the sodium bromide surfactant solutions. The solubilizing power of the sodium bromide solutions was somewhat higher than that of the quaternary ammonium halide solutions. The surface activity of the quaternary ammonium halides could most probably be attributed to the salt effect when they were introduced into the micellar systems. The zwitterionic compounds were essentially surface inactive.