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Title: Some properties of aqueous solutions of cetyl trimethyl ammonium bromide in the presence of substituted benzoic acid salts
Author: Ferguson, James M.
Awarding Body: University of Glasgow
Current Institution: University of Glasgow
Date of Award: 1949
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This work is chiefly concerned with the properties of aqueous solutions of cetyl trimethyl ammonium bromide (CTAB) in the presence of certain additives which are mainly derivatives of benzoic acid such as sodium salicylate or sodium p-chlorobenzoate. In the first part of the work, the adsorption of CTAB from its aqueous solutions on to graphite alumina, titanium dioxide and silica has been studied. In all cases, the CTAB appears to be adsorbed by an ion exchange process. A bimolecular layer is formed. In the first layer, the ionic head of the CTA+ is held to the surface by chemical forces while the paraffin chain is oriented away from the surface and in the second layer, the reverse orientation occurs. The effect of seven benzoic acid salts on the amount of CTA+ adsorbed on alumina has been found to be qualitatively related to their effects on the viscosity of CTAB solutions. The sodium salicylate - CTAB system has been examined in more detail and an adsorbed film containing equimolecular amounts of salicylate and CTA+ has been found to form on alumina. The salicylate - CTA+ complex covers a greater part of the surface than the CTA+ alone and consequently gives a better measure of the surface area of the powder. The sedimentation volume of titanium dioxide in CTAB solutions has also been investigated and the effect of sodium salicylate y sodium p-chlorobenzoate and sodium p-hydroxybenzoate on this sedimentation volume has been related to their effects on the viscosity of CTAB solutions. In the second part of the work, the approximate activity coefficient of Br in CTAB solutions was measured using electrolytically prepared silver-silver bromide electrodes. The critical micelle concentrations of CTAB (in .002M KBr) and of dodecyl trimethyl ammonium bromide were determined by this method and found to agree with the values obtained by other workers. The activity coefficient of Br was also measured in solutions containing CTAB and salts similar to those used in the adsorption and sedimentation work. Changes in the activity coefficient of Br on addition of these salts were again found to be related to their effects of the viscoity of CTAB solutions. Finally, a preliminary attempt was made to investigate the elastic properties of the visco-elastic solutions. These solutions were contained in the gap between two vertical co-axial glass cylinders which were caused to oscillate harmonically. The response of the liquid was observed by focussing a microscope on a very small bead which had been suspended in the liquid. The results again showed that the salicylate -CTA+ complex acquires some stability when the salicylate and the CTA+ are present in equimolecular amounts. The structure of the solutions, particularly the p-chlorobenzoate - CTA+ solutions, seems to be altered on shearing. An effort has been made to interpret the results of different types of experiments in terms of long threadlike aggregates formed by interaction of the CTA+ with the organic salt.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available