Micellization and Counterion Binding Behavior of Cetylpyridinium Chloride in Aqueous Solutions of Sodium Bromide and Tetrabutylammonium Bromide

Critical micelle concentrations (CMC) of cetylpyridinium chloride (CPC) in aqueous sodium bromide and tetrabutylammonium bromide (TBAB) solutions were determined at 30 °C by conductivity and surface tension measurements. Bromide counterions reduce CMC of CPC more than the chloride. The modified form of the Corrin-Harkins (CH) equation describes the variation of CMC of CPC with the concentration of added electrolyte containing different counterions. It is demonstrated that the mixed-electrolyte-model (MEM) of Shanks and Franses can be applied to analyze the conductivity data of the surfactant solution containing mixed counterions, which was otherwise used for a surfactant solution containing single counterion only. The value of the total counterion binding constant (β) obtained from the MEM was then used to separate from the slope of the modified CH equation the counterion binding constants for chloride (β1) and bromide (β2) ions. This data analysis showed that binding of bromide counterion to cetylpyridinium ionic micelle is stronger than that of the chloride counterion, which is in accordance with the positions of chloride and bromide ions in the Hoffmeister series and the results reported from other studies.

Effects of interfacial specific cations and water molarities on AOT micelle-to-vesicle transitions by chemical trapping: the specific ion-pair/hydration model

Added salts induce micelle-to-vesicle transitions at specific cation concentrations in Hofmeister order by forming polar headgroup–counterion pairs that release water.

The equilibrium and dynamic surface tension of polymeric surfactants based on epoxidized soybean oil grafted hydroxyethyl cellulose

Analysis of the equilibrium and dynamic surface tension of epoxidized soybean oil grafted hydroxyethyl cellulose (H-ESO-HEC) surfactants with different molecular weights were carried out at pH values that ranged from 8 to 13.