Cetyltrimethylammonium bromide surfactant

Kuczynski and Thorns also studied the formation of MV in CdS solution using a cationic surfactant, cetyltrimethylammonium bromide, as a stabiliasr. In the presence of ethylenediaminetetraacetate (EOTA), the MV " yield was greatly increased. EDTA and MV " form a complex with a resultant negative charge, which is electrostatically bound to the cationic CdS surface. The MV " formed is repelled by the positive charge of the cationic stabilizer, a fact which makes the charge separation efficient. 

It is seen from Table 11.1 that surfactant cetyltrimethylammonium bromide (CTAB, RN MexBr ) exerts a positive catalytic effect on ethylbenzene autoxidation. The kinetic study of this phenomenon [21,27] showed that the acceleration was caused by the additional reaction of hydroperoxide with the bromide ion of CTAB to form free radicals [30],... 

The surfactant, cetyltrimethylammonium bromide, was dissolved in water to obtain a clear solution, in which the first swelling agent (decane) was then added drop by drop with stirring. After ten minutes stirring at room temperature, the second swelling agent (TMB) was introduced. Sodium silicate was added to the obtained micellar solution and the pH value was adjusted with sulfuric acid. The pH value and surfactant/silicium molar ratio was fixed at 10 and 0.62 according to the protocol established previously for conventional MCM-41 synthesis... 

Pure silica mesostructures were prepared using both electrostatic surfactant (cetyltrimethylammonium bromide, CTAB) assembly and neutral alkylamine (octylamine and dodecylamine) assembly. Thus, tetraethoxysilane (TEOS) was added to solutions of framework-forming surfactants and stirred for 24 hours. The exact conditions for the synthesis procedures are described in a previous publication.20 Although Soxhlet extraction over ethanol was used to remove the framework-bound surfactant molecules from the amine-assembled mesostructures, 650°C calcination was necessary to remove the CTAB from the... 

Nanosized metal sulfide powders of Ag2S, CuS, FeS, Ga2S3. In2S3, MnS, NiS, and ZnS were synthesized for use as gas- and liquid-phase mercury sorbents. An aqueous-based synthesis method using the surfactant cetyltrimethylammonium bromide (CTAB) is described. The vapor- and aqueous-phase mercury-sorption characteristics of the nanocrystalline powders synthesized and of commercially produced Ag2S, AU2S. and AU2S3 are presented. 

Between hydrophobic surfaces a completely different interaction is observed. Hydrophobic surfaces attract each other [184], This attraction is called hydrophobic interaction. The first direct evidence that the interaction between solid hydrophobic surfaces is stronger than the van der Waals attraction was provided by Pashley and Israelachvili [185,186], With the surface force apparatus they observed an exponentially decaying attractive force between two mica surfaces with an adsorbed monolayer of the cationic surfactant cetyltrimethylammonium bromide (CTAB). Since then the hydrophobic force has been investigated by different groups and its existence is now generally accepted [189]. The origin of the hydrophobic force is, however, still under debate. 

The majority of the recipes described in the literature are based on the anionic sodium dodecylsulfate (SDS) as a model system. The possibility of using cationic surfactants such as octadecyl pyridinium bromide for the preparation of miniemulsions was first exploited in 1976. However, the emulsions were prepared by stirring and the resulting emulsions showed broadly distributed droplet sizes [2,39,50]. Recent work on steady-state miniemulsions showed that cationic and nonionic surfactants form well-defined miniemulsions for further miniemulsion polymerization processes, resulting in narrow size distributed stable cationic and nonionic latex particles [51]. Similar molecular amounts of the simple cationic surfactant, cetyltrimethylammonium bromide or chloride... 

The surfactant-aided Lewis acid catalysis was first demonstrated in the model reaction shown in Table 13.1 [22]. While the reaction proceeded sluggishly in the presence of 10 mol% scandimn triflate (ScfOTOs) in water, a remarkable enhancement of the reactivity was observed when the reaction was carried out in the presence of 10 mol% Sc(OTf)3 in an aqueous solution of sodium dodecyl sulfate (SDS, 20 mol%, 35 mM), and the corresponding aldol adduct was obtained in high yield. It was found that the type of surfactant influenced the yield, and that Triton X-100, a non-ionic surfactant, was also effective in the aldol reaction (but required longer reaction time), while only a trace amount of the adduct was detected when using a representative cationic surfactant, cetyltrimethylammonium bromide (CTAB). The effectiveness of the anionic surfactant is attributed to high local concentration of scandium cation on the surfaces of dispersed organic phases, which are surroimded by the surfactant molecules. 

The seeds are then added to a growth solution that consists of fresh metal salt, and a surfactant, cetyltrimethylammonium bromide, CTAB, that directs the growth of nanopartides into nanorods and nanowires. Growth is initiated by the addition... 

Kita and co-workers built on the results of previous studies to report EPHP-mediated cyclisation of hydrophobic substrates in water.13 This breakthrough was made possible by running the reactions in the presence of a water-soluble initiator (VA-061) and a surfactant [cetyltrimethylammonium bromide (CTAB)]. The authors explained this outstanding result as being due to the micellar effect generated by CTAB, as in its absence the reaction proceeds to the extent of only 25%. The organic ammonium group of CTAB probably contributes to the incorporation of the hypophosphoric acid in the micelles (Scheme 5.3). 

This methodology was applied to synthesis of 2/,3/-didehydro-2/,3/-dideoxy-nucleosides, potent anti-HIY agents. The bis-xanthate of the V3-methyluridine derivative was subjected to radical reaction conditions in water, giving the corresponding alkene in 82% yield. Similar results were also achieved in the case of the adenosine derivative (76% yield). However, Kita et al. found that the combination of a water-soluble radical initiator, 2,2 -azobis[2-(2-imid-azolin-2-yl)propane] (VA-061), a water soluble chain carrier, 1-ethylpiperidine hypophosphite (EPHP), and a surfactant, cetyltrimethylammonium bromide (CTAB), resulted in a radical cyclisation that occurred in water with a variety of hydrophobic substrates16 (Table 5.2). 

Although the mesophases prepared by Liu et al. [4] did not show X-ray reflections in the wide-angle range (> 5 °2Q), the solids showed an enhanced thermal stability [3-5] in comparison with conventional mesoporous materials. Following this approach we will describe here the crystallization of ZSM-5 seeding gel in the presence of the cationic surfactant cetyltrimethylammonium bromide known as structure directing agent for different mesophases [1]. 

Ranjan RS, Qian Y, Krishnapillaj M. (2006). Effects of electrokinetics and cationic surfactant cetyltrimethylammonium bromide [CTAB] on the hydrocarbon removal and retention from contaminated sods. Environmental Technology 27 767-778. 

Farias and co-workers [30] reported the synthesis of thin hybrid films made of PANI and a ceramic used in the technological industry, titanium dioxide, which were prepared via the layer-by-layer self-assembly technique. Aiming to improve the dispersion of the ceramic in the polymer matrix, the commercial surfactant, cetyltrimethylammonium bromide (CTAB), was used during the formation of the... 

Nagai and coworkers reported a study of heterocoagulation driven by the hydrophobic effect of cationically charged hard poly[styrene-C( -(methacryloy-loxyphenyl-dimethylsulfonium methylsulfate)], or soft poly[styrene-co-(butyl acrylate)-co-(methacryloyloxyphenyl-dimethylsulfonium methylsulfate)] latex particles of ca. 220-240 nm in diameter onto neutral microspheres of crosslinked polystyrene (8.5[im in diameter) [37]. A separate study on the small cationic latex particles showed that their interface was hydrophobic, as the cationic surfactant cetyltrimethylammonium bromide (CTAB) adsorbed onto the surface, clearly driven by a hydrophobic effect [38]. The assembly of the cationic latex particles onto the larger microspheres was studied against increasing NaCl concentrations, which influenced the packing patterns from individually spaced to clusters (see Fig. 5). 

NMR self-diffusion measurements indicated that all microemulsions consisted of closed water droplets and that the structure did not change much during the course of reaction. Hydrolysis was fast in microemulsions based on branched-chain anionic and nonionic surfactants but very slow when a branched cationic or a linear nonionic surfactant was employed (Fig. 11). The cationic surfactant was found to form aggregates with the enzyme. No such interactions were detected with the other surfactants. The straight-chain, but not the branched-chain, alcohol ethoxylate was a substrate for the enzyme. A slow rate of triglyceride hydrolysis for a Ci2E4-based microemulsion compared with formulations based on the anionic surfactant AOT [61,63] and the cationic surfactant cetyltrimethylammonium bromide (CTAB) [63] was observed in other cases also. Evidently, this type of lipase-catalyzed reaction should preferably be performed in a microemulsion based on an anionic or branched nonionic surfactant. Nonlipolytic enzymes such as cholesterol oxidase seem to function well in microemulsions based on straight-chain nonionic surfactants, however [64]. CTAB was reported to cause slow inactivation of different types of enzymes [62,64,65] and also, in the case of Chromobacterium viscosum lipase [66], to provide excellent stability. 

The successful homocouphng of aryl and heteroaryl bromides and chlorides was achieved by using palladium on charcoal in the presence of sodium hydroxide, sodium formate, and a surfactant (cetyltrimethylammonium bromide, etc.) (Scheme 6). The advantage of this procedure is that the homocoupling of aryl and heteroaryl halides can be successfully achieved (Table... 

One can conceive that an anionic surfactant like sodium-di-2-ethylhexyl-sulfosuccinate (NaAOT) or sodium dodecyl sulfate (SDS) can be called so in working terms when the positively charged counterion, sodium, gets detached from the molecule and is released into the solvent in which the surfactant is dissolved. The same is true for the surfactant cetyltrimethylammonium bromide (CTAB) in which case the negatively charged bromide ion should be detached from the molecule so that the latter can become cationic . 

X-hDTNB CN--S --SOi Application of the cationic surfactant cetyltrimethylammonium bromide. Binary mixtures may be determined in the 10 moll range using the multiple linear regression method... 

Mixed micelles can be exploited as templates for preparation of nanoporous materials. Oligomeric alkyl-ethylene oxide surfactant (Polyoxyethylene (2) cetyl ether, B52), and ionic surfactant (cetyltrimethylammonium bromide, CTAB) form mixed micelles that self-assemble into well-ordered hexagonal and bimodal mesostructures. These systems can be used as templates to synthesize hydrothermally stable organized periodic mesoporous organosilicas (PMOs). The X-ray diffraction (XRD), TEM, BET, NMR and hydrothermal studies have been used to investigate the effects of B52 on the formation of various PMOs. The addition of B52 in the surfactant solution improves... 

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