Reverse emulsion technique

As the pore size of these DMCs is too small to accommodate the reactant molecules, the catalytic activity of these materials is confined to the outer surface of the particles. The synthesis of nanoparticles using a reverse emulsion technique, therefore, further increased the catalytic activity of the materials. Comparison of these Zn-Co-DMC materials with the Ztf -exchanged zeolite H-p as a reference material moreover showed that DMC materials were both more active and selective catalysts. 

Similar grafting experiments by the emulsion technique were described (34) in the system vinyl chloride/copolymer butyl methacrylate-methacrylic acid and in the reverse system, and also in the system styrene/polyvinyl chloride. In this last case again as in homogenous medium, the inverse process failed (vinyl chloride on polystyrene). Grafted acrylonitrile copolymers were also prepared in order to improve their dyeability, by polymerizing acrylonitrile in emulsion in the presence of many different polymers as polyvinyl alcohol, polymethacrylamide and polyvinylpyrrolidone (119, 120, 121), polyvinyl acetate and polyacrylic acid (115), wool (224,225), proteins (136), etc. 

In this paper we examine the role of mixed surfactants in the demulsification of water-in-Leduc oil emulsion by application of the spreading rate method which is then correlated with the electroacoustic results and centrifugation. Microelectrophoresis using the reverse emulsion was also used to investigate the adsorption process. The results show both a very good correspondence between the various techniques and provide insight on the synergistic adsorption behavior of the hydrophobic and hydrophilic surfactants. 

Kanagasabapathy, S., Sudalai, A., and Benicewicz, B. C. (2001). Reversible addition-fragmentation chain-transfer polymerization for the synthesis of poly(4-acetoxystyrene) and poly(4-acetoxystyrene)-block-polystyrene by bulk, solution and emulsion techniques. Macromol. Rapid. Commun., 22(13) 1076-1080. 

PtRu nanoparticles can be prepared by w/o reverse micro-emulsions of water/Triton X-lOO/propanol-2/cyclo-hexane [105]. The bimetallic nanoparticles were characterized by XPS and other techniques. The XPS analysis revealed the presence of Pt and Ru metal as well as some oxide of ruthenium. Hills et al. [169] studied preparation of Pt/Ru bimetallic nanoparticles via a seeded reductive condensation of one metal precursor onto pre-supported nanoparticles of a second metal. XPS and other analytical data indicated that the preparation method provided fully alloyed bimetallic nanoparticles instead of core/shell structure. AgAu and AuCu bimetallic nanoparticles of various compositions with diameters ca. 3 nm, prepared in chloroform, exhibited characteristic XPS spectra of alloy structures [84]. 

Pulsed gradient spin-echo (PGSE) NMR techniques have also been employed to study the structure of the oil phase [12]. This gives an idea of the mobility of each component in the HIPE, and showed that, for stable emulsions and HIPEs, the oil phase was indeed a reverse micellar solution which solubilises water. Further work using PGSE NMR has shown that water can diffuse between aqueous droplets in concentrated emulsions [101]. Presumably this involves solubilisation of the water molecules by the micellar oil phase. 

Very recently, ESR techniques have been employed to study the packing of surfactant molecules at the oil/water interface in w/o HIPEs [102,103], By including an amphiphilic ESR probe, which is adsorbed at the oil/water interfaces, it is possible to determine the microstructure of the oil phase from the distribution of amphiphiles between the films surrounding the droplets and the reverse micelles. It was found that most of the surfactant is located in the micelles, over a wide range of water fraction values. However, when the water content is very high (water droplets of the emulsion, to stabilise the large interfacial area created. 

Determination of drug potency in the presence of other emulsion components may require development of special analytical techniques for example, oils may interfere with standard reverse phase HPLC assays, requiring extraction techniques or the development of normal phase assays. Similarly, bioassays may give erroneous results when the drug is presented in an emulsion form. Hence, adequate controls and/or extraction techniques must be developed to give reliable values from the bioassay. 

Before the growth of organic chemistry and techniques for sulfonating fats and oils, tanners emulsified oils for leather softeners with soap and protective colloids. These mixtures were prepared as water-in-oil emulsions, called mayonnaise in the trade and added to the water in the drum with the leather. They are still used but not nearly as frequently as sulf(on)ated oils. On the other hand, salts of naphthenic acid are used with hydrocarbon oils (e.g., 11) to make the reverse forms of these. 

Controlled free-radical polymerization (CFRP) has been used successfully to produce block, graft, and other controlled architecture copolymers within the last decade for a variety of free radically polymerizable monomers. The main techniques include reversible addition fragmentation and transfer (RAFT) polymerization, stable free-radical polymerization (SFRP) mediated by nitroxide/alkoxyamine based radicals, atom transfer radical polymerization (ATRP), diphenyl ethylene (DPE) mediated polymerization, and novel precipitation/emulsion polymerization based methods like free-radical retrograde precipitation polymerization (FRRPP). ... 

Taking into account all of the above mentioned applications, the synthesis of magnetic latex will be discussed in two parts first, the preparation of iron oxide nanoparticles and, second, the preparation of magnetic latex. Depending on the aim of researchers, many polymerization techniques are applied such as suspension, dispersion, emulsion, microemulsion and miniemulsion polymerization in combination with controlled radical polymerization techniques like atom transfer radical polymerization (ATRP), reversible addition-fragmentation chain transfer (RAFT) and nitroxide-mediated radical polymerization (NMP). The preparation of hybrid magnetic latex by emulsion polymerization will be the focus of this review. 

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