Ammonium bromide, CTAB

Surfactants employed for w/o-ME formation, listed in Table 1, are more lipophilic than those employed in aqueous systems, e.g., for micelles or oil-in-water emulsions, having a hydrophilic-lipophilic balance (HLB) value of around 8-11 [4-40]. The most commonly employed surfactant for w/o-ME formation is Aerosol-OT, or AOT [sodium bis(2-ethylhexyl) sulfosuccinate], containing an anionic sulfonate headgroup and two hydrocarbon tails. Common cationic surfactants, such as cetyl trimethyl ammonium bromide (CTAB) and trioctylmethyl ammonium bromide (TOMAC), have also fulfilled this purpose however, cosurfactants (e.g., fatty alcohols, such as 1-butanol or 1-octanol) must be added for a monophasic w/o-ME (Winsor IV) system to occur. Nonionic and mixed ionic-nonionic surfactant systems have received a great deal of attention recently because they are more biocompatible and they promote less inactivation of biomolecules compared to ionic surfactants. Surfactants with two or more hydrophobic tail groups of different lengths frequently form w/o-MEs more readily than one-tailed surfactants without the requirement of cosurfactant, perhaps because of their wedge-shaped molecular structure [17,41]. 

Cetyl trimethyl ammonium bromide [CTAB]/w-alkanol [13-15]... 

Sonawane et al. [90] investigated the affect of ultrasound and nanoclay for the adsorption of phenol. Three types of nanoclay tetrabutyl ammonium chloride (TBAC), N-acetyl-N,N,N trimethyl ammonium bromide (CTAB) and hexadecyl trimethyl ammonium chloride (HDTMA), modified under sonication, were synthesized which showed healthier adsorption of phenol within only 10 min in waste water. The interlamellar spacing of all the three clay increased due to incorporation of long chain quaternary salts under cavitational effect. 

Surface-active agents used as adjuvants in pharmaceutical preparations to improve drug dissolution may affect the stability of /3-lactams. Thus, the presence of micelles of cetyl(trimethyl)ammonium bromide (CTAB) enhanced up to 50-fold the rate of alkaline hydrolysis of penicillins [140]. In the case of cephalosporins, micelle-promoted catalysis of the intramolecular degradation process (see Sect 5.2.2) was also observed [85][141], It has been proposed that the negatively charged penicillins and cephalosporins are attracted by the cationic micelles. This attraction increases substrate concentration in the micellar phase, in turn accelerating the rate of HO- ion attack. Ion exchange at the micellar surface and electrostatic stabilization of the transition state may also contribute to the increased rate [142][143],... 

Systems and materials. The reaction was carried out at several compositions in an ionic and in a nonionic system. The ionic system consisted of an emulsifier (49.6 wt % cetyltrimethyl ammonium bromide (CTAB)/50.4% n-butanol), hexadecane, and water. The nonionic emulsifier consisted of 65.7% polyoxyethylene (10) oleyl ether (Brij 96) and 34.4% n-butanol, again with hexadecane and water. In both systems, mlcroemulslon (pE) compositions used were obtained by diluting an initial 90 weight percent (%) emulsifler/10% oil mixture with varying amounts of water. Micro-emulsion samples thus obtained had final compositions of 30 to 80% water. Phase maps describing these systems have been published (10-11). 

Since N will be larger than S+, all anionic surfactants are negatively charged. Similarly, cationic micelles will be positively charged. For instance, the cationic surfactant cetyltrimethyl ammonium bromide (CTAB), we have following equilibrium in micellar solutions ... 

Contrary to hydrotropes, micelle-forming surfactants spontaneously self-aggregate cooperatively above the critical micelle concentration (cmc) even in the absence of solubilizate. Typical examples of micelle-forming surfactants include sodium dode-cylsulfate (SDS), dodecyltrimethylammonium bromide (DTAB), cetyltrimethyl-ammonium bromide (CTAB), and heptaoxyethylene dodecyl ether (C12E7) (Scheme 2). 

Surfactants such as cetyl trimethyl ammonium bromide (CTAB), Triton X-100 (TX-lOO) and sodium dodecyl sulphate (SDS) are the most commonly used. CTAB forms large micelles [24-26] with aggregation number 61, cmc 9.2 X 10 M, and a positive micellar Stem layer TX-lOO has aggregation number 139 with neutral OH groups on the Stern layer, and SDS forms negative micelles with cmc 8.3 x 10 M and aggregation number 131. The... 

Cetyltrimethyl ammonium bromide (CTAB) dodecyltrimethyl ammonium bromide (DTAB) tetradecyltrimethyl ammonium bromide (TTAB) trioctyl-methyl ammonium chloride (TOMAC) N-benzyl-N-dodecyl-hf-bis(2-hy-droxy ethyl) ammonium chloride (BDBAC) cetyl pyridinimn chloride (CPC) quaternary ammonium salt with carbon atoms of R ranging from 8-10 (CHj Rj N+ CL) (Aliquat 336)... 

For interpreting thesedata, and as a first step towards formulating a model for monolayer penetration, it is clearly desirable to calculate the amount of surfactant that has penetrated the monolayer. This has proved to be a difficult theoretical problem, but in recent years some limited solutions and a general solution have been found. In this paper we examine data for the penetration of cholesterol monolayers by hexadecy1-trimethyl-ammonium bromide (CTAB) (7) and compare the penetration or adsorption values calculated from the different treatments. 

Numerical data are available from our earlier penetration work for a number of monolayer/surfactant systems. The simplest of these systems was selected for this initial analysis the penetration of cholesterol monolayers by hexadecyl-trimethyl-ammonium bromide (CTAB) J). Cholesterol monolayers at 298 K exhibit a single, highly incompressible, condensed phase with the transition to a gaseous phase occurring at a negligibly low surface pressure. CTAB does not appear to undergo surface hydrolysis (10) and the gaseous-to-expanded phase transition occurs at a low concentration (0.043 mmol kg ) and a low surface pressure (1.0 mN m l). 

Schultz and Matijevic (16) prepared nanoparticles of palladium sulfide (PdS) by the continuous double-jet mixing of PdCl2 or Na2(PdCl4) and Na2S. They found that the particle size was 20-30 nm in mean diameter obtained in acidic media (pH = 2-3), but 2-5 nm in alkaline media, probably due to the high equilibrium concentration of sulfide ions S2- by dissociation of H2S and HS in the alkaline media (pH = 10-12). A cationic surfactant, cetyl trimethyl ammonium bromide (CTAB), was found to be useful for stabilizing the small particles prepared in alkaline media. 

The effect of various surfactants, the cationics-eetyl trimethyl ammonium bromide (CTAB), and cetyl pyridinium chloride (CPC), the anionic-sodium lauryl sulfate (SLS), and the nonionic-polysorbate 80 (Tween 80), on the solubility and ionization constants of some sparingly soluble weak acids of pharmaceutical interest was studied (Gerakis et al., 1993). Benzoic acid (and its 3-methyl-, 3-nitro-, and 4-tert-butyl-derivatives), acetylsalicylic acid, naproxen, and iopanoic acid were chosen as model drugs. The cationics, CTAB and CPC, were found to considerably increase th< ionization constant of the weak acidS Ka ranged from-0.21 to-3.57), while the anionic, SLS, showed a negligible effect and the nonionic, Tween 80, generally decreased the ionization constants Solubility of the acids increased in aqueous micellar and in acidiLed micellar solutions. 

Baxendale, Evans and coworkers reported in 1946 that the polymerization of methyl methacrylate (MMA) in aqueous solution was characterized by homogeneous solution kinetics, i.e. where mutual termination of free radicals occurred, in spite of the fact that the polymer precipitated as a separate phase. Increases in the rates of polymerization upon the addition of the surfactant cetyl trimethyl ammonium bromide (CTAB) were attributed to the retardation of the rate of coagulation of particles, which was manifested in a reduction in the effective rate constant for mutual termination,... 

In this area, recent unrelated efforts of the groups of Bhattacharya and Fife toward the development of new aggregate and polymer-based DAAP catalysts deserve mention. Bhattacharya and Snehalatha [22] report the micellar catalysis in mixtures of cetyl trimethyl ammonium bromide (CTAB) with synthetic anionic, cationic, nonionic, and zwitterionic 4,4 -(dialkylamino)pyridine functional surfactant systems, lb-c and 2a-b. Mixed micelles of these functional surfactants in CTAB effectively catalyze cleavage of various alkanoate and phosphotriester substrates. Interestingly these catalysts also conform to the Michaelis-Menten model often used to characterize the efficiency of natural enzymes. These systems also demonstrate superior catalytic activity as compared to the ones previously developed by Katritzky and co-workers (3 and 4). 

Several approaches to develop an improved JEV vaccine are in progress in various laboratories. Of these, immunization of mice with plasmid DNA encoding JEV envelope (E) protein has shown great promise. The technology, developed by Kaur et al. [232], involved the adsorption of DNA onto cetyltrimethyl-ammonium bromide (CTAB) containing cationicpoly(lactide-co-glycolide) (PLG) microspheres. 

The vast majority of miniemulsion polymerizations reported in the literature have been stabilized with anionic surfactants, probably because of the widespread application of anionic surfactants in macroemulsion polymerization, and due to their compatibility with neutral or anionic (acid) monomers and anionic initiators. However, Landfester and coworkers [70, 71] have used the cationic surfactants cetyltrimethyl ammonium bromide (CTAB) and cetyltri-methyl ammonium tartrate for the production of styrene miniemulsions. They report that these surfactants produce similar particle sizes to anionic surfactants used at the same levels. Bradley and Grieser [72] report the use of dodecyltrimethyl ammonium chloride for the miniemulsion polymerization of MMA and BA. 

Eliasson and Ljunger (33) reported that the cationic surfactant cetyl trimethyl-ammonium bromide (CTAB) slowed down the rate of formation of amylopectin crystallites in gelatinized waxy maize starch, as measured by differential scanning calorimetry (DSC). 

Fig. 1. 1H chemical-shift dependence on the concentration of surfactants, Triton X-100 (TX-100) and cetyl trimethyl ammonium bromide (CTAB). 

All chemicals were obtained reagent grade from Aldrich Chemical Company. The liquids were passed through a column of Woelm Act. I alumina for purification, and were subsequently dried and storaged over 4A molecular sieves. The cetyltrimethyl-ammonium bromide (CTAB) was twice recrystallized from acetone. 

The liver is homogenized in a solution which contains ATP (final concentration 0.01 M) and MgS04 7H20, (final concentration 0.01 Af) adjusted to pH 6.7 at 37°C with solid KHCO3. This homogenate is diluted 1 1 with cetyl ammonium bromide (CTAB) a final liver concentration of 1 in 10 is achieved, and the preparation is kept cold imtil used. 

Chemicals. N,N-dimethyldodecylamine-N-oxide (DDAO) and cetyl trimethyl-ammonium bromide (CTAB) were purchased from Fluka Chemical Corp. Cetyl pyridinium chloride (CPC) and polyoxyethylene nonyl phenyl ether, with an average degree of polymerization of 10 (NP(EO)2q) were obtained from Hexacel Corp. and... 

Competitive displacement of spread (3-lactoglobulin from an air-water interface by (a) nonionic and (b) ionic surfactants. The collapse of the protein network is indicated by showing the change in area occupied by the protein at the interface as a function of surface pressure, (a) Data for A-Tween 20 (polyoxyethylene sorbitan monolaurate) and B-Tween 60 (polyoxyethylene sorbitan momostearate). (b) Data for A-cetyl-trimethyl-ammonium bromide (CTAB), B-lyso-phosphatidylcholinelauroyl (LPC-L), and -sodium dodecyl sulphate (SDS). 

AFM images showing the displacement of a spread (3-lactoglobulin protein film from an air-water interface by the progressive addition of surfactant, (a) Displacement with (polyoxyethylene sorbitan monolaurate) Tween 20, surface pressure Tr=22.5mN/m, image size 3.2 X 3.2 jam. (b) Displacement with cetyl-trimethyl-ammonium bromide (CTAB), TT = 22.8 mN/m, image size 1x1 /rm. (c) Displacement with CTAB in the presence of 0.2 M sodium phosphate buffer, pH — 7, ir— 22.8 mN/m. scan size 1x1 /rm. Data are shown at similar surface pressures in order to allow comparison of domain sizes for ionic and nonionic surfactants. 

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