Cetyltrimethylammonium emulsion

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... 

Using distribution between chloroform and water, Jones and asso-ciates have separated an acetylated mixture of neutral polysaccharide, which dissolved in the chloroform, and an acidic polysaccharide, which formed an emulsion between the two phases. Such mixtures were shown by Scott < to be easily separated by precipitation of the acidic component with such quaternary ammonium salts as cetyltrimethylammonium (Cetavlon) or cetylpyridinium halides. Polysaccharides which differ in acidity can also be separated by this method, and, as the solubility of the precipitate increases with increasing ionic strength, the separation can also be done as... 

A rather unusual procedure has been published for the palladium- and copper-catalyzed synthesis of triarylamines, using an alkaline water-ethanol emulsion stabilized by cetyltrimethylammonium bromide [41]. Anyway, this method overcomes the problem in the synthesis of N-aryl carbazoles (Eq. 14), which are not accessible by the method developed by Hartwig and Buchwald [42],... 

In emulsions, amine hydrochloride constitutes the aqueous phase and acrylic ester the organic phase. Cetyltrimethylammonium bromide (CTAB) or span/twin (S/T)-type surfactants are used for emulsion polymerization. Solid dispersants such as talc and colloidal silica are often used to stabilize emulsions which are difficult to stabilize with usual surfactants. Hydrophilic colloidal silica (Aerosil 200) drastically increases the stability of some emulsions provided high amounts (up to 10%) of Aerosil are used. Random copolymers containing 10% hydroxyl groups can be used as polymeric dispersants for preparing w/o emulsions. 

The addition of various surfactants and micelle-forming agents in the biphasic hydroformylation of olefins was also considered as a tool for enhancement of the reaction rates (see Section 2.3.4). Whereas the presence of a surfactant leads to a lower droplet size in the dispersed phase, thus increasing the liquid-liquid interfadal area and hence the mass-transfer rate, the formation of emulsions is considered as a maj or drawback of this system. Mass-transfer effects in biphasic hydroformylation of 1-octene in the presence of cetyltrimethylammonium bromide (CTAB) was studied by Lekhal et al. [37]. A mass-transfer model based on Higbie s penetration theory was proposed to predict the rate of hydroformylation in a gas-liquid-liquid system. 

Calix[n]arenes 1-3 were used as inverse PT catalysts in the alkylation of active methylene compounds with alkyl halides in aqueous NaOH solutions,and in aldol-type eondensation and Michael addition reactions. In the aikylation of phenylacetone with octyl bromide, the IPTC procedure enhanced the alkylation versus hydrolysis and C versus O alkylation selectivities with respect to those observed xmder classical PTC reactions in the presence of tetrabutylammonium bromide (TBAB) or hexadecyltributylammonium bromide (HTPB). Moreover, the aqueous catalyst solution was easily separated from the organic phase eontaining the products, and no organic solvent was required. In the case of the aldol-type condensation of benzaldehyde with indene or acetophenone in aqueous NaOH (Fig. 9), IPTC reaetions eatalyzed by I were compared with those conducted in aqueous micelles in the presence of cetyltrimethylammonium bromide (CTAB) as the sufactant. Although selectivities and yields were similar, the IPTC proeedure avoided the formation of emulsions, thus faciUtating product separation and catalyst recovery. In the light of the results obtained, water-soluble calix[ ]arenes 1-3 were proposed... 

The kinetic studies performed on the polymerization of MMA in the emulsion and microemulsion regions of ternary systems based on cetyltrimethylammonium bromide (CTAB) confirmed the difference in mechanisms between the two processes [84,91]. The following kinetic laws were obtained ... 

A highly porous polymeric foam can be prepared through emulsion templating by polymerizing the continuous phase of high internal phase emulsions [150], A maleimide-terminated aryl ether sulfone oligomer was copolymerized with divinylbenzene in the continuous phase, using a mixed surfactants system, cetyltrimethylammonium bromide, dodecylbenzene-sulfonic acid sodium salt, and a peroxide initiator. The polymers show a CO2 adsorption and improved mechanical properties. The materials exhibit an open cell and a secondary pore structure with surface areas of a 400 m g ... 

Anionic surfactants (such as sodium dodecyl sulfate), cationic surfactants (such as cetyltrimethylammonium bromide) (163), and nonionic surfactants (such as the polyoxyethylenated alkylphenols) (136,338) have been used in preparing emulsions. Different types of surfactants can be used in the same recipe (377) to provide additional stability under specific conditions. For example, mixtures of anionic and nonionic surfactants are common. The anionic surfactant controls the particle nucleation stage, and the nonionic surfactant imparts additional electrolyte tolerance, mechanical shear stability (345), and freeze-thaw stability. Mixtures of anionic and cationic surfactants tend to coagulate and are to be avoided. 

Colloid Polymer Science 214, No.8, Aug. 1996, p.772-8 FORMATIONS OF POLYVINYL TOLUENE MICROLATEXES IN QUATERNARY OIL IN WATER CETYLTRIMETHYLAMMONIUM BROMIDE EMULSIONS Santhanalakshmi J Anandhi K Madras,University... 

Cationic micelles, such as those formed from cetyltrimethylammonium bromide, may also accelerate reaction. Studies involving reactions with alkoxide ions indicate that factors involved include the concentration of reagents within the micelle, desolvation of the alkoxide ions, and stabilization of the transition state [92]. There have also been studies of the effects of oil-water emulsions [93] and vesicles [94] on reactivity, and ionic liquids have been shown to accelerate the ethanolysis of l-fluoro-2,4-dinitrobenzene [95]. 

Rambhau et al. [28] found that the stability of emulsion can be evaluated through zeta-potential measurements. Aging of emulsions prepared with cetyltrimethylammonium bromide (CTAB) under accelerated aging conditions (temperature or centrifugation) resulted in an increase in particle size, and decrease in viscosity and zeta-potential. An inverse correlation was observed between zeta-potential and aging. The maximum zeta-potential was associated with the maximum emulsion stability (Fig. 24). 

Scheme 1 Emulsion polymerization of methyl styrene and catalytic oxidation of poly(methyl styrene) latexes to the corresponding aldehyde and carboxylic acid groups. [AINB = a,a -azobrsisobutyromitrile, CTAB = cetyltrimethylammonium bromide, V-50 = 2,2 -azobis(2-amidinopropane) dihydrochloride]...

Yang et al reported the emulsion and suspension polymerization of styrene in the presence of montmorillonite modified with various modifying agents such as cetyltrimethylammonium chloride, cetylpyridinium bromide. 

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