The aqueous cetyl trimethylammonium bromide solutions

Ekwall, Per; Mandell, Leo; Solyom, Peter

doi:10.1016/0021-9797(71)90210-4

Cited by 248 publications

(134 citation statements)

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“…[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%

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: 99%

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

et al. 2012

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“…20 Particularly, we are interested in studying the surfactant cetyltrimethylammonium bromide, [CH 3 (CH 2 21 has applications in DNA extraction, and is widely used in the synthesis of metallic nanoparticles as a stabilizer and growth-driving agent of nanoparticles. 22,23 Its 1 st and 2 nd CMCs in water are 0.92 mM 24 and 0.27 M, 25 respectively, and its Krafft temperature is 298 K. 26 As expected, the counterions (bromide) are located near the external positively charged border of the CTA + aggregates; however, it is important to mention that many assembly properties, such as the morphology, size, charge, and intra-micellar interactions, depend on the nature of the counterion. 27,28 This is particularly evident if one compares the structural properties of CTAB and CTAC, [CH 3 (CH 2 …”

Section: Introductionmentioning

confidence: 98%

Molecular Dynamics Simulations of Cetyltrimethylammonium Bromide (CTAB) Micelles and their Interactions with a Gold Surface in Aqueous Solution

Silva¹,

Dias²,

Hora³

et al. 2017

J. Braz. Chem. Soc.

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Surfactants are molecular structures with remarkable physicochemical properties and applications. Most of their characteristics are due to their ability to promote aggregation and interactions with different interfaces. The scarcity of theoretical studies dedicated to evaluating the forces involved in these interactions prompted us to propose other models capable of reproducing the experimental data in better ways. We carried out molecular dynamics (MD) simulations to obtain a model for cetyltrimethylammonium bromide (CTAB), selected from gromos54a7 force field parameters, that better describes most of its behaviors in aqueous solution (micellar structure, counterion dissociation, etc.) and its adsorption pattern on a gold surface. The parameters adopted for one of the models were able to mimic several characteristics suggested by experimental measurements of the CTAB micelles, as well their adsorption pattern on a gold surface. Indeed, this model was able to obtain quasi-spherical micelles, as well as a pattern of adjacent cylindrical micelles with alkyl chain interactions on a gold surface.Keywords: molecular dynamics, micelles, interface interaction, cetyltrimethylammonium bromide, gold IntroductionSurfactants are a class of compounds containing a polar group, charged or neutral, attached to a long hydrophobic tail.1,2 These are remarkably versatile compounds with a broad variety of important applications in the pharmaceutical, medical, and food industries and for nanomaterial synthesis.3,4 Above a certain temperature in solution (the Krafft temperature), surfactants tend to aggregate to minimize unfavorable interactions between the surfactants and the surrounding environment. 5 The minimum concentration required for surfactant aggregation is defined as the critical micellar concentration (CMC), and most of the characteristics of these aggregates are controlled by factors such as the solvent type, chemical structure of the surfactant, and solution conditions (e.g., concentration, temperature, presence of additives, and ionic strength). 6Variations of these factors yield aggregates with different morphologies such as spherical or ellipsoidal micelles, cylindrical or thread-like micelles, disk-like micelle, membranes and vesicles.7 These self-assembled structures have been characterized by a number of techniques, such as dynamic light scattering (DLS), 8 nuclear magnetic resonance (NMR), 9,10 fluorescence spectroscopy, 11 quasielastic neutron scattering (QENS), 12,13 small-angle X-ray scattering (SAXS), 14,15 and small-angle neutron scattering (SANS). 16,17 Computational simulations have also been employed to explore the structures and dynamical behaviors of micelles for different surfactants. 18Considering that no holes exist within a micelle, its radius is estimated as the maximum extension of a hydrocarbon chain and can be evaluated by using the following equation:where l max is the maximum length in nm and n C is the number of carbon atoms in the chain. 19 Indeed, under the previously mentioned conditions, ...

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“…CTAB is a kind of cationic surfactants consisting of a polar hydrophilic head group and a non-polar hydrophobic tail. When the concentration of CTAB was more than critical micelle concentration (CMC), corresponding to ~ 0.006 mol/L in this experiment, a micelle structure begins to be formed where the size and morphology of CTAB micelle are influenced by CTAB concentration pH and salts [8][9][10]. On the other hand, a lot of LaF 3 :Eu 3+ nucleus seeds were at first produced after the addition of NaF into the mixture of La 3+ /Eu 3+ aqueous solution (see Experimentals) and adsorbed by the hydrophobic tail of CTAB and finally located inside CTAB micelle.…”

Section: Experimentalsmentioning

confidence: 93%