Effects of added dotab on thecmc and enthalpy of micelle formation at 298.2 K for CTAB(aq)

Abstract

In a titration calorimetric study an aqueous solution held in a syringe and containing hexadeeyltrimethylammonium bromide (CTAB; 15.4x10 -3 tool dm -3) is injected in aliquots (5• 10 -3 dm 3) into a sample cell containing initially water. Analysis of the data shows that the cmc equals 0.97x10 -3 dm -3 and the enthalpy of micelle formation equals -10.3 kJ mol -l. When the solution in the syringe is replaced by a mixed surfaetant solution, CTAB+dodeeyltrimethylam-monium bromide, at the same total concentration of surfactant, the cmc of CTAB decreases gradually with increasing mole fraction of DOTAB but the enthalpy of CTAB mieelle formation is hardly affected. We conclude, therefore, that incorporation of DOTAB monomers into the CTAB micelles stabilizes entropieally the CTAB micelles.

Debye Length and Double-Layer Forces in Polyelectrolyte Solutions

“…As seen in Table , our theoretical predictions are at least as good (even slightly better at the higher micelle concentrations) as the empirical expression of P−N, which is purely heuristic and was not theoretically derived. Note that only the two highest CTAB concentrations are significantly higher than the cmc of 9.7 × 10 -4 M and hence contain a considerable amount of micelles. We should also note that the range of distances used by P−N was mostly larger than the size of the micelles of ∼3−4 nm, and it is therefore not obvious whether the micelles and their counterions remained between the surfaces when the theories of Borukhov et al. , are expected to hold or whether the micelles were depleted from between the surfaces when eq 28 should hold.…”

“… a Note that the total surfactant concentration [CTAB] in column 1 includes both the free CTAB monomers in solution at the critical micelle concentration (cmc) of n s = 9.7 × 10 - 4 M (ref ) and the CTAB molecules in micelles. …”

Electrochemical detection of single micelles through ‘nano-impacts’

“… 21 – 23 Due to its importance, the critical micelle concentration (CMC) of this standard micellar agent is well-studied. 24 – 27 …”

“…[21][22][23] Due to its importance, the critical micelle concentration (CMC) of this standard micellar agent is well-studied. [24][25][26][27] Herein, the detection of CTAB micelles is performed through the electrochemical method of 'nano-impacts'. The electrochemical oxidation of CTAB was rst studied on a macro electrode system and compared to the oxidation of free bromide ions in aqueous solution.…”

Model Alkali-Soluble Associative (HASE) Polymers and Ionic Surfactant Interactions Examined by Isothermal Titration Calorimetry

“…Some publications on the rheological properties of HASE polymers in surfactant solutions have recently appeared. − However, the macroscopic characterization using rheological techniques do not provide detailed insights into the microscopic interactions. With the recent development in microcalorimetry, this technique may be exploited to elucidate micellization behavior of surfactants and the microscopic interactions in mixed surfactant solutions , and polymer−surfactant systems. Some modeling results based on the technique were presented by Blandamer and co-workers. , This technique has been used to study the interactions of surfactant with unmodified polymers. − Only very few studies focused on hydrophobically modified polymeric systems. − Thus, in this paper, we seek to examine the interactions of SDS with a series of model HASE polymers containing various types of hydrophobes.…”