Growth and counterion binding of cetyltrimethylammonium bromide aggregates at 25.degree.C: a neutron and light scattering study

Quirion, François; Magid, L. J.

doi:10.1021/j100412a108

Cited by 125 publications

(114 citation statements)

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“…Cross-sections for cylindrical micelles are reported to be equal or even slightly smaller (< 10%) than the corresponding spherical systems in many systems ranging from classical surfactants like CTAB 33 to glucose based compounds. 39,40 Nevertheless, a 40% difference as observed in SL is too large to be explained by chain conformation, packing or curvature differences, as usually done.…”

Section: E-mentioning

confidence: 95%

“…[31][32][33][34][35][36][37][38] Furthermore, in the specific case of alkylpolyglucosides (APG), no pH-driven long-range ordering of micelles is found until concentration values reach at least 10-20 wt%. 12,[39][40][41] On the contrary, long-range intermicellar interactions for these systems can be controlled at lower concentrations by adding specific electrical charges at the micellar outer surface using ionic surfactants.…”

Section: E-mentioning

confidence: 99%

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Unusual, pH-Induced, Self-Assembly Of Sophorolipid Biosurfactants

et al. 2012

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International audienceAn increasing need exists for simple, bioderived, nontoxic, and up-scalable compounds with stimuli-responsive properties. Acidic sophorolipids (SL) are glucose-based biosurfactants derived from the yeast broth of Candida bombicola (teleomorph: Starmerella bombicola). The specific design of this molecule, a sophorose head with a free end-COOH group at the end of the alkyl chain, makes it a potentially interesting pH-responsive compound. We have specifically investigated this assumption using a combination of small angle neutron scattering (SANS), transmission electron microscopy under cryogenic conditions (Cryo-TEM), and nuclear magnetic resonance (NMR) techniques and found a strong dependence of SL self-assembly on the degree of ionization, α, of the COOH group at concentration values as low as 5 and 0.5 wt %. At least three regimes can be identified where the supramolecular behavior of SL is unexpectedly different: (1) at low α values, self-assembly is driven by concentration, C, and micelles are mainly identified as nonionic objects whose curvature decreases (sphere-to-rod) with C; (2) at mid α values, the formation of COO– groups introduces negative charges at the micellar surface inducing an increase in curvature (rod-to-sphere transition). Repulsive electrostatic long-range interactions appear at this stage. In both regimes 1 and 2, the cross-section radius of the micelles is below 25 Å. This behavior is concentration independent. (3) At α = 1, individual micelles seem to favor the formation of large netlike tubular aggregates whose size is above 100 nm. Such a complex behavior is very unique as it is generally not observed for common alkyl-based surfactants in concentration ranges below 5–10 wt %

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Section: E-mentioning

confidence: 95%

Section: E-mentioning

confidence: 99%

Unusual, pH-Induced, Self-Assembly Of Sophorolipid Biosurfactants

et al. 2012

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“…41 This micelles structure established from the fits is similar to those reported in the literature for CTA + systems determined by SAXS or SANS. [49][50][51][52][53][54][55][56][57] It should be mentioned here that the fit is restricted to q values greater than 0.02 Å -1 , to avoid the low-q region where an extra contribution to the intensity is measured, whose origin is not understood. Interestingly, no interaction peak is observed, as one would expect from this system at the concentration used here (3.10 -2 M).…”

Section: Cylindrical Vs Spherical Micellesmentioning

confidence: 99%

In Situ Time-Resolved SAXS Study of the Formation of Mesostructured Organically Modified Silica through Modeling of Micelles Evolution during Surfactant-Templated Self-Assembly

et al. 2012

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The mechanisms of formation of organically modified (phenyl, vinyl, and methyl) silica materials with cubic Pm3̅n and hexagonal p6m periodic mesostructures obtained in one step in the presence of the cetyltrimethylammonium bromide (CTA+B) surfactant are reported in this study. Understanding the way these complex materials form is difficult but undoubtedly necessary for controlling the material structure and its properties because of the combined presence of surface organic groups and large surface areas. Here, the mechanism of formation is clarified on the basis of the modeling of time-resolved in situ small angle X-ray scattering (SAXS) experiments, with a specific focus on the micelle evolution during material formation. Their fast self-assembly is followed for the first time with a quick temporal resolution of a few seconds using a third-generation synchrotron radiation source. To better understand the behavior of the complex organic-containing mesostructure, we perform a comparative study with the corresponding organo-free, isostructural materials obtained from three different surfactants (CTA+, CTEA+, and CTPA+) having a constant chain length (C16) and an increasing polar head volume (met-, et-, and prop-). Numerical modeling of SAXS data was crucial to highlighting a systematic sphere-to-rod micellar transition, otherwise undetected, before the formation of the 2D hexagonal phase in both organo-free and organo-containing systems. Then, two different pathways were found in the formation of the cubic Pm3̅n mesostructure: either an ordering transition from concentrated flocs of spherical micelles (from CTEA+ or CTPA+) for pure TEOS systems or a structural transformation from an intermediate 2D hexagonal mesophase in organosilane systems (from CTA+). Combining the comparison between organo-free and organo-containing systems with numerical modeling, we find that the hexagonal-to-cubic phase transition in the organically modified materials seems to be strongly influenced not only by the obvious presence of the organic group but also by the quicker and more massive condensation kinetics of silicate oligomers on the CTA+ micellar surface. Finally, quite unexpectedly, we find a wormlike-to-sphere micellar transition in the CTPA+ system.

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“…The critical micelle concentrations (CMCs) and the degree of micellar counterion dissociation (α) have been measured by various methods such as electromotive force (EMF), conductivity, light scattering, NMR and small angle neutron scattering (SANS) measurements (1)(2)(3)(4)(5)(6).…”

mentioning

confidence: 99%

Convenient Estimation for Counterion Dissociation of Cationic Micelles Using Chloride-Sensitive Fluorescence Probe

Asakawa

Kitano

Ohta

et al. 2001

Journal of Colloid and Interface Science

105

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The concentration dependent properties exhibit a break point due to the micellization.The CMC of surfactant is usually determined by plotting those properties as a function of concentration. The other important property of ionic surfactant solutions is the degree of micellar counterion dissociation, which has been used to be quantified by the two-site model (7,8). From this simple model one can calculate the α by using the concentrations of "free" ions in the aqueous bulk phase and "bound" ions in micellar phase. The model has successfully The MQAE probe was developed to study the transport of chloride ion in liposomes (11).The MQAE are highly polar and membrane impermeant, which has suitable physical properties for measurement of the concentration of free chloride ion. When the cationic MQAE is introduced to cationic surfactant solutions, the MQAE will tend to partition in aqueous bulk phase due to the low octanol-water partition coefficient in addition to the electrostatic effect.The fluorescence behavior of water-soluble MQAE can be expected to related to the chloride ion concentration in aqueous bulk phase. Fig. 2 shows the Stern-Volmer plots for quenching of MQAE fluorescence by various cationic surfactants. The fluorescence intensities of MQAE 5 were found to decrease in the presence of CTAC, TTAC, TDBAC and DAC. The observed quenching can be ascribed to the free chloride ion dissociated from the surfactant. All experimental data gave linear plots below their CMCs. The slopes of plots, K SV , below CMC are summarized in Table 1. The K SV for CTAC agreed very closely with that of NaCl. The K SV for surfactant monomer tend to decrease with decreasing length of the alkyl chain. The decrease in

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Growth and counterion binding of cetyltrimethylammonium bromide aggregates at 25.degree.C: a neutron and light scattering study

Cited by 125 publications

References 0 publications

Unusual, pH-Induced, Self-Assembly Of Sophorolipid Biosurfactants

Unusual, pH-Induced, Self-Assembly Of Sophorolipid Biosurfactants

In Situ Time-Resolved SAXS Study of the Formation of Mesostructured Organically Modified Silica through Modeling of Micelles Evolution during Surfactant-Templated Self-Assembly

Convenient Estimation for Counterion Dissociation of Cationic Micelles Using Chloride-Sensitive Fluorescence Probe

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