Interpretation of Conductivity Results from 5 to 45 °C on Three Micellar Systems below and above the CMC

Abstract

Electrical conductivity has been used at different temperatures to study three micellar systems: tetradecyltrimethylammonium chloride (TTACl), dodecyltrimethylammonium chloride (DTACl), and decyltrimethylammonium chloride (DeTACl). A phenomenon of premicellization is observed for DeTACl and DTACl below the critical micellar concentration (CMC). Association constants are introduced in the MSA-transport theory to correctly reproduce experimental conductivity and also calculate the effective charge of the micelles and their degree of dissociation. Various mechanisms are considered to explain premicellization. The formation of a neutral pair followed by an association involving two monomers and a counterion appears to be the most probable first step in the premicellization process.

Polymer-induced ordering and phase separation in ionic surfactants

“…For the cases (a)-(c) the phase separation occurs for sufficiently high mass fraction of polyelectrolyte or nonionic polymer and salt. In the case (d) the phase separation was not observed.The values of the critical micelle concentrations (the concentrations of surfactants above which the micelles are spontaneously formed in the solution) for the surfactants used in experiments are the following: CTAB: 0.9 mM[32]; TTAB: 3.86 mM[33]; DTAC: 21.5 mM[34]; CPB: 0.65 mM[35]; SDS: 8.16 mM[36]; DSS: 8.55 mM[37].…”

Pierre Turq, an inspirational scientist in charge and at interfaces

“…The group has also extended this analytical approach to various complex systems (see following sections), including e.g. micellar systems [7,8], clay powders [9,10], or humic and fulvic acids, which are ionised in aqueous solutions [11,12]. This latter application is illustrated in Figure 1.…”

“…If the normal mode approach used then still remains insightful [38], other analytical theories (mainly MSA transport) have been successfully used to assess the charge and the radius of micellar aggregates from conductivity measurements, taking into account the interactions between all charged species in solution [7]. This method has also proven successful to determine the extent of premicellization, that is, the formation of small surfactant aggregates before the critical micellar concentration; the shorter the chain of the surfactant, the larger the premicellisation [8].…”

“…Conversely, the comparison with experiments demonstrated the shortcomings of the force fields used in molecular simulations [60,61]. Understanding the dynamics of interlayer cations on the molecular scale allowed to propose a simple diffusion/adsorption scheme [62], which was then used to model some relaxation processes for the interpretation of dielectric spectroscopy experiments [8,9,63]. The group further studied the dynamics and thermodynamics of water and ion exchange between the smallest (interlayer) and larger From ab initio simulations to investigate the reactivity of surface sites to highly coarse-grained models described in Section 3, including many studies on the molecular scale using classical molecular simulations.…”

Aggregation of sodium dodecylsulfate in aqueous nitric acid medium

“…Two approaches are used for quantifying the size of monomeric ion of any surfactant by assuming an equivalent-sphere concept. In the first approach [5,6,22,23] radius of the dodecylsulfate ion (DS) is estimated by using the Stokes-Einstein relation…”