Application of Microelectrode Voltammetry to Study the Properties of Surfactant Solutions: Alkyltrimethylammonium Bromides

Abstract

Microelectrode cyclic voltammetry (MV) has been employed to investigate the micellar properties of solutions of homologous alkyltrimethylammonium bromides, RMe(3)ABr, R = C(10), C(12), and C(14), in water and in the presence of added NaBr. The micellar self-diffusion coefficient was calculated from the limiting current for the reversible electron transfer of micelle-bound ferrocene. From the values of this property, other parameters were calculated, including the micellar hydrodynamic radius, R(H), and aggregation number, N(agg); the latter was also theoretically calculated. We determined the values of the diffusion coefficient as a function of various experimental variables and observed the following trends: The diffusion coefficient decreases as a function of increasing surfactant concentration (no additional electrolyte added); it decreases as a function of increasing surfactant concentration at fixed NaBr concentration; and it shows a complex dependence (increase then decrease) on the NaBr concentration at a fixed RMe(3)ABr concentration. The value of the intermicellar interaction parameter decreases and then increases as a function of increasing NaBr concentration. These results are discussed in terms of intermicellar interactions and the effect of NaBr on the micellar surface charge density and sphere-to-rod geometry change. The NaBr concentration required to induce the latter change increases rapidly as a function of decreasing the length of R: no geometry change was detected for C(10)Me(3)ABr. Values of N(agg) increase as a function of increasing the length of R and are in good agreement with both literature values and values that were calculated theoretically. Thus, MV is a convenient and simple technique for obtaining fundamental properties of surfactant solutions, including additive-induced changes of micellar parameters (N(agg)) and morphology changes.

Electrolyte effect on adsorption and the phase transition from microstructures to nanostructures in ionic/ionic surfactants mixture

“…6 shows the reversibility of ferrocene in this system. The electrochemistry of ferrocene in nonaqueous, aqueous, and micellar environments is described elsewhere [46][47][48][49][50].…”

Self-assembled catanionic surfactant mixtures in aqueous/ionic liquid systems

“…3 shows the reversibility of ferrocene in this system. The electrochemistry of ferrocene in nonaqueous, aqueous, and micellar environments is described elsewhere [18][19][20][21][22]. In CV, the peak current i pa obtained by cyclic voltammogram and diffusion coefficient is given by the Randles-Sevcik equation [23]:…”

Electrochemical Analysis of Aqueous Benzalkonium Chloride Micellar Solution and Its Mediated Electrocatalytic De-Chlorination Application

“…With the exception of BKC, many other self-aggregated surfactant monomers have been used to solubilize redox species in solution, and they have been analyzed by the electrode surface [12,13]. Advantageous of this phenomena used to harvest the physicochemical properties of the various surfactant solutions by single potential step chronoamperometry [14,15] and diffusion limiting current at micro-electrodes techniques [16,17]. Despite the interesting physicochemical identification of surfactants in electrochemistry, the mediated catalytic reduction of halo compounds, such as 4-bromobiphenyl, 4,4'-dichlorobiphenyl, allyl chloride, and PCB (Polychlorinated biphenyls) mixtures, catalyzed by different organic and inorganic mediators, e.g., 9-phenylanthracene [18], [Co(bpy) 3 ] 2+ (where bpy = 2,2'-bipyridine) [19,20], zinc phthalocyanine [21], etc., have been observed in aqueous solutions of various surfactants, such as CTAB (Cetyltrimethylammonium bromide), SDS (Sodiumdodecyl sulfate), and film-forming dodecyl dimethyl ammonium bromide.…”