Effect of Ionic Surfactants on Ion Vibration Current and Colloid Vibration Current

Abstract

In order to clarify the effect of constituent ions on an electroacoustic phenomenon in an aqueous solution of ionic surfactant, we measured the total vibration current TVI as a function of the molarity of aqueous solution of several ionic surfactants at 298.15 K under atmospheric pressure. The different counterion caused the remarkable change in TVI, while the difference in alkyl chain length of surfactant ion hardly affected TVI. This suggests that the size and/or aggregation number of micelle is not a crucial factor contributing to TVI. Employing the fl uorocarbon surfactant, on the other hand, there appeared a fairly large change compared to the hydrocarbon surfactant. This implies that the density contrast between medium and micelle is signifi cant for TVI.

Study on Colloid Vibration Current in Aqueous Solution of Binary Surfactant Mixtures: Effects of Counterions and Hydrophobic Chains

“…6 . On the basis of a previous study 3 , this result is attributable to the difference in density between the micelle and water rather than the ζ-potential of the micelle surface. As shown in Section 3.2, the micelle composition curve 4 in Fig.…”

“…In the previous study 3 , we showed that the CVI values of fluorocarbon surfactant, LiFOS, are significantly larger than those of hydrocarbon surfactant, LiDS, and it was concluded that this difference is due to the significant difference in density between the micelle and the surrounding medium, i.e. ρ p -ρ 0 in Eq.…”

“…At all compositions, the TVI values increased linearly with increasing molarity, and a break point appeared on each curve. In our previous studies 2, 3 , we proved that the concentration at the break point corresponds to the cmc see the dotted line in Fig. 3 , and the TVI values at the concentration regime below the cmc provide information regarding the surfactant monomer whilst the TVI values at concentrations above the cmc give information concerning the surfactant micelle.…”

“…Electroacoustic phenomena are a type of electrokinetic phenomenon 1 , and in previous studies 2, 3 we have investigated electroacoustic phenomena in aqueous solutions of ionic surfactants. By vibrating the micelle particles in aqueous solution using ultrasonic irradiation, a distorted electrical double-layer is formed around the micelle particles, which results from the combination of the heavier micelle core and the lighter counterions in the electrical double-layer, and the cations and anions are periodically collected in the solution.…”

“…2 The CVI values were affected by the type of counterion due to the difference in ζ-potential between different micelle particles. 3 The alkyl Abstract: In order to elucidate an electroacoustic phenomenon of mixed micelles in an aqueous solution, we measured the colloid vibration current (CVI) in aqueous solutions of binary surfactant mixtures. Based on the thermodynamic treatment of critical micelle concentration (cmc) values determined by conductivity measurements, it was expected that dodecyltrimethylammonium bromide (DTAB) and dodecyltrimethylammonium chloride (DTAC) molecules would mix ideally in the micelle.…”