The Determination of the CMC of Surfactants in Some Organic Solvents

Abstract

Extra absorption spectra appeared when 7,7,8,8-tetracyanoquinodimethane (TCNQ) was solubilized into surfactant organic solvent solutions above the critical micelle concentration (CMC). It was found also that extra absorption spectra appeared when iodine was solubilized into surfactant organic solvent solutions above the CMC. In the former case, the extra absorption spectra are attributed to TCNQ anion radical salts formed between TCNQ and the surfactants. In the latter, the extra absorption spectra are due to charge-transfer interactions of iodine with the surfactants. The intensity of the absorption bands increased with the concentrations of the surfactant. The values of the CMC of the surfactants were determined from this spectral change. The CMC values obtained by the TCNQ solubilization method were larger than those obtained by the iodine solubilization technique. The difference in the CMC between the two methods was interpreted in terms of the difference in solubility and chargetransfer power to the organic solvent between iodine and TCNQ, and the difference in type of electron transition, that is, n(D)→σ(A) or n(D)→π(A).

The effect of solvent and counterion variation on inverse micelle CMCs in hydrocarbon solvents

“…Experimentalists, however, have succeeded in measuring transitions that are consistent with a step change from monomers to inverse micelles at a critical concentration [14][15][16][17][18][19][20][21][22]. Accurate and consistent values of CMCs for inverse micelle formation are lacking in the literature.…”

“…Accurate and consistent values of CMCs for inverse micelle formation are lacking in the literature. Several groups have used techniques as disparate as iodine solubilization and mercury interfacial tension to measure CMCs for AOT in different organic solvents, but the results are highly variable between the different studies [15,16,19,20,23,24].…”

Influence of the Oil on the Properties of Microemulsions as Reaction Media

“…The bulk solvent is known to affect various micellar properties, including the critical micelle concentration, [44] the size of w/o microemulsions, [45] and solvent penetration into the interface. [12] As a result, the properties of water molecules dissolved in the core can be influenced by the nature of the solvent.…”

Interaction between tetracyanoethylene and naphthalene in reverse micelles of AOT in n-hexane. The electron-donor properties of AOT

“…As well, in the previously studied I,-AOT system (18) we found that AOT may act as a "n" donor, probably through the free electron pair on carbonyl gr0up.s present in the ester functions. Also, an n-n* EDA interaction have been proposed between AOT and 7,7,8,8-Tetracyanoquinodimethane (TCNQ) in several organic solvents (19). Thus, it may be that AOT competey with Naph in the association with TCNE.…”

“…(13). Moreover, although no Ks(2) values were calculated, it has been shown that AOT interacts so strongly wirh TCNQ (19) that the spectra of the anion radical of this acceptor is detected in reverse micelle systems.…”