Supramolecular systems based on cationic surfactants: an influence of hydrotropic salts and oppositely charged polyelectrolytes

Abstract

For cationic surfactant 4-aza-1-dodecyl-1-azoniabicyclo[2.2.2]octane bromide (DABCO-16), a significant decrease in the critical micelle concentration (CMC) is shown in the presence of hydrotropic salts, which is due to the efficient binding of organic counterions with the surface of micelles and charge compensation of the head groups. The effect of salts increases in the series sodium benzoate < sodium tosylate < sodium salicylate. In the presence of hydrotropes, the electrokinetic potential decreases and the size of the aggregates increases. For micellar solutions DABCO-16 in the presence of sodium tosylate and sodium salicylate, the viscosity of the solution increases significantly, which is not observed in the case of sodium benzoate. In the presence of strong polyelectrolyte sodium polystyrenesulfonate, an increase in the critical aggregation concentration is observed compared to the CMC of an individual DABCO-16 solution, whereas weak polyelectrolyte polyacrylic acid induces a significant decrease in the aggregation threshold of the surfactant. Both polyelectrolytes exert no substantial effect on the rheological properties of micellar systems.