Elektrolit varlığında iyonik bir sürfaktanın miselleşme özellikleri üzerine ortamın dielektrik sabitinin etkisi

Micellization properties of cationic dodecyltrimethylammonium bromide (DTMABr) surfactant were studied in the absence and presence of some electrolytes in polar organic solvents/water mixtures. The selected electrolytes were LiBr, NaBr, KBr, RbBr, and CsBr, whose cations prefer to be located in the intermicellar region (Gouy-Chapman or diffuse layer), and KF and KCl, whose anions tend to be bound to the micelle surfaces in the Stern layer. While some of those ions exhibit kosmotropic behaviour, others have chaotropic behaviour. The effect of the dielectric constant of the bulk solution was also investigated by varying the polar organic solvents ethylene glycol (EG) and formamide (FA) concentrations in the solutions. The micellization parameters (micellization Gibbs energy, ∆𝐺𝑚𝑖𝑐 , degree of counterion from micelle, α, and degree of counterion binding to micelle, β) were evaluated from electrical conductivity measurements. Zeta potential measurements were performed to find some valuable information about the change in thickness of the layers around the micelles. The average micelle diameters were determined from Small-angle X-ray scattering measurements. All results indicated that both the specific interactions between ionic species and the dielectric constant of the medium have crucial effects on the micellization properties of surfactants.