An elaborate investigation on the transition of rod-like micelle of cetyltrimethylammonium p-toluenesulfonate in presence of different additives

Abstract

Abstract The noticeable change in self-aggregation nature (rod-like micelle) of cetyl trimethylammonium p-toluene sulfonate (CTAT) in presence of various electrolytes and non-electrolytes was probed using tensiometry, conductometry, isothermal titration calorimetry and fluorimetry. The impact of electrolytes and non-electrolytes on the critical micelle concentration (CMC) of the surfactant was found to be opposite of each other. The non-electrolytes having lower dielectric constants than water increased the repulsion between the surfactant head groups, thereby increasing the CMC. Less negative value of ΔG0m with increase in solvent concentration indicated delayed process of micellization. On the contrary, electrolytes decreased the CMC by a large extent due to suppression of the repulsion between the charged head groups by supplying more counter ions from the salts. The aggregation number of CTAT solution in presence of electrolytes increased with increase in salt concentration but decreased in presence of non-electrolytes, with increase of its concentration. The packing parameter value indicated the transition towards spherical shape with increase in concentration of non-electrolytes and increase in more non-spherical shape with increase in concentration of electrolytes for rod-like micelles of CTAT.