Polymerization of microemulsions

Corpart JM, Candau F (1993) Formulation and polymerization of microemulsions containing a mixture of cationic and anionic monomers. Colloid Polym Sci 271(11) 1055-1067... 

Similarly, electrolytes play a major role in the stability of the final latices. Polymerization of AH microemulsions in the absence of salt gives unstable latices, even at high surfactant concentrations. When salts with high salting-out efficiency (sodium acetate) are added to the systems, stable and clear microlatices are produced. Polymerization of microemulsions containing a polymerizable salt leads, under appropriate conditions, to the formation of stable microlatices (11,29). 

Styrene polymerization in microemulsions yields a different morphology compared to bulk polymerization. Preliminary results have been reported earlier (24.251. The solids obtained by polymerization of microemulsions are opaque, as opposed to transparent polystyrene obtained from bulk polymerization. The opacity is due to the presence of the surfactant. SEM micrographs imUcate porous structures in the solid materials obtained by jwlymeriang microemulsions. Figure 5(a) shows the structure of styrene polymeriz in bulk. As expected, it... 

Nanocapsules Prepared by Interfacial Polymerization of Microemulsions, Proceedings of the 27th International Symposium on Controlled Release of Bioactive Materials of the Controlled Release Society, Inc., Paris, France, July 9-13, 2000 Abstract 6138. 

Polymerization of microemulsions that contains IL polar cores dispersed in a polymerizable oil has been reported for the system styrene/[C mim][BF ]/[MAUM][Br] where [MAUM][Br] is 1-(2-methyl acryloyloxyundecyl)-3-methylimidazolimn bromide and was used to stabilize [C mim][BF4]/styrene microemulsions [91]. In the same way, Texter and coworkers [92] use a ternary microemulsion formed by MMA/[C mim] [BF4]/[Cj2mim][Br] instead of an aqueous microemulsion for atom transfer radical polymerization showing that after the polymerization and isolation of the resultant polymers, the mixture of the catalyst and ILs (continuous phase and surfactant) can be recovered and reused improving the environmental sustainabihty of the processes. The rate of the polymerization process can be improved by using a new IL, BPYP-[MIM] PF, that combines properties of surfactants and catalyst hgands [93] (see Scheme 13.3). 

Graetzel CK, Jirousek M, Graetzel M (1986) Photoredox-induced polymerization of microemulsion droplets. Langmuir 2 292-296... 

IL microemulsions have also been used for the fabrication of pol3mier electrolyte membranes (Yan et al., 2009). These nonaqueous proton conducting membranes have been prepared via the polymerization of microemulsions comprising PILs, surfactant and a... 

Yu et al. reported for the first time the preparation and polymerization of microemulsions that contain IL polar cores dispersed in polymerizable oil comprising surfactant-stabilized IL nanodomains. 

Fig. 5. Polymerizable surfactant used to prepare proton conducting membranes via the polymerization of microemulsions.

In 2009, the same research group published the second paper in proton conducting membranes via the polymerization of microemulsions containing nanostructured Protic ILs (PILs) networks. PILs nanostructures formed in the precursor microemulsions could be preserved in the resultant polymeric matrix without macroscopic phase separation, even if the produced vinyl polymers are incompatible with PIL cores. 

Other solubilization and partitioning phenomena are important, both within the context of microemulsions and in the absence of added immiscible solvent. In regular micellar solutions, micelles promote the solubility of many compounds otherwise insoluble in water. The amount of chemical component solubilized in a micellar solution will, typically, be much smaller than can be accommodated in microemulsion fonnation, such as when only a few molecules per micelle are solubilized. Such limited solubilization is nevertheless quite useful. The incoriDoration of minor quantities of pyrene and related optical probes into micelles are a key to the use of fluorescence depolarization in quantifying micellar aggregation numbers and micellar microviscosities [48]. Micellar solubilization makes it possible to measure acid-base or electrochemical properties of compounds otherwise insoluble in aqueous solution. Micellar solubilization facilitates micellar catalysis (see section C2.3.10) and emulsion polymerization (see section C2.3.12). On the other hand, there are untoward effects of micellar solubilization in practical applications of surfactants. Wlren one has a multiphase... 

Microemulsion Polymerization. Polyacrylamide microemulsions are low viscosity, non settling, clear, thermodynamically stable water-in-od emulsions with particle sizes less than about 100 nm (98—100). They were developed to try to overcome the inherent settling problems of the larger particle size, conventional inverse emulsion polyacrylamides. To achieve the smaller microemulsion particle size, increased surfactant levels are required, making this system more expensive than inverse emulsions. Acrylamide microemulsions form spontaneously when the correct combinations and types of oils, surfactants, and aqueous monomer solutions are combined. Consequendy, no homogenization is required. Polymerization of acrylamide microemulsions is conducted similarly to conventional acrylamide inverse emulsions. To date, polyacrylamide microemulsions have not been commercialized, although work has continued in an effort to exploit the unique features of this technology (100). 

Emulsifiers are used in many technical applications. Emulsions of the oil-in-water and the water-in-oil type are produced on a large scale in the cosmetic industry. Other fields of employment are polymerization of monomers in emulsions and emulsification of oily and aqueous solutions in lubricants and cutting oils. In enhanced oil recovery dispersing of crude oil to emulsions or even microemulsions is the decisive step. 

By performing in situ the polymerization of acrylamide in water/AOT/toluene microemulsions, clear and stable inverse latexes of water-swollen polyacrylamide particles stabilized by AOT and dispersed in toluene have been found [192-194], It was shown that the final dispersions consist of two species of particles in equilibrium, surfactant-coated polymer particles (size about 400 A) with narrow size distribution and small AOT micelles (size about 30 A). 

Polymerization in microemulsions allows the synthesis of ultrafine latex particles in the size range of 5 to 50 nm with a narrow size distribution [33], The deposition of an ordered monolayer of such spheres is known to be increasingly difficult as the diameter of such particles decreases [34], Vigorous Brownian motion and capillary effects create a state of disorder in the system that is difficult... 

In a reverse microemulsion, the hydrolysis and polymerization of the silicate precursor occur in the water droplet, therefore, to dope dyes in the silica nanoparticles they must be water soluble. However, a number of organic dye molecules are hydrophobic, requiring modifications prior to doping. Several methods are available to link a hydrophobic dye molecule to a water soluble group. A simple and effective example is to link a hydrophilic dextran to the dye molecules [8]. This modification can greatly enhance the water solubility of hydrophobic dye molecules, but will increase the cost of resultant DDSNs. 

In contrast to the highly interconnected pores mentioned previously, closed pores can also be obtained by microemulsion polymerization if the initial volume fraction of the dispersed phase is kept lower than 30%. Recently two systems have been reported where the polymerization of the continuous phase and the subsequent removal of the Hquid dispersed phase resulted in the formation... 

Microemulsion polymerization is an emulsion polymerization with very much smaller monomer droplets, about 10-100 nm compared to 1-100 pm. Micelles are present because the surfactant concentration is above CMC. The final polymer particles generally have diameters of 10-50 nm. Although many of the characteristics of microemulsion polymerization parallel those of emulsion polymerization, the details are not exactly the same [Co et al., 2001 de Vries et al., 2001 Lopez et al., 2000 Medizabial et al., 2000]. Water-soluble initiators are commonly used, but there are many reports of microemulsion polymerization with... 

Another area of microemulsion application is in the synthesis of certain polymers. The process is called emulsion polymerization, a misnomer since micelles rather than emulsion drops are the site of the polymerization reaction. Because of the commercial importance of polymers, this process has been extensively researched and is quite well understood. We only consider some highlights of the process. 

Microemulsion polymerizations follow a different mechanism from the conventional emulsion polymerizations. The most probable locus of particle nucle-ation was suggested to be the microemulsion monomer droplets [27], although homogeneous nucleation was not completely ruled out. The particle generation rate in microemulsion polymerization is given by an expression similar to Eq. (21), which was used for the miniemulsion polymerization of styrene [28] ... 

A microemulsion, Fig. 1, has a similar organization to that characteristic of a micelle but employs, rather than one, multiple surfactant components, allowing for introduction of other additives into the hydrophobic core [11], As with micelles, microemulsions are optically transparent and can be easily studied by standard spectroscopic methods. One important use of such microemulsions is in the photoinduced initiation of polymerization of monomers with low water solubility many such reactions involve a mechanism occurring through photoinduced interfacial electron transfer. 

Another interesting heterogeneous polymerization using macromonomers is a microemulsion copolymerization to produce particles 10-100 nm in diameter. Gan and coworkers [150] have prepared transparent nanostructured polymeric materials by direct polymerization of bicontinuous micro emulsions consisting... 

Polymerization of LB films, or deposition of LB films on polymers, offers the opportunity to impart to LB films a higher degree of mechanical integrity. However, preliminary work in this direction shows a conflict between the chainlike primary structure of the polymer and the well-organized supramo-lecular structure [15]. One possible solution may be the insertion of flexible spacers between the main chain polymer and the side chain amphiphile, a route also employed in liquid crystal polymers. These materials belong to an interesting class of two-dimensional polymers, of which there are few examples. These toughening techniques may eventually be applied to stabilize other self-assembled microstructures, such as vesicles, membranes, and microemulsions. 

Shang et al. (61) used microemulsion polymerization to synthesize MWCNT-PMMA composites for gas sensor applications. Better dispersion, enhanced electrical conductivity and better sensor response was observed for in-situ fabricated composites compared to composites prepared by solution mixing. Ma et al. (62) performed in-situ polymerization of MWCNT-PMMA composites in the presence of an AC electric field to study dispersion and alignment of MWCNT in PMMA matrix induced by the electric field. Experimental evidences from in-situ optical microscopy, Raman spectroscopy, SEM and electrical conductivity showed that both dispersion and alignment qualities were significantly enhanced for oxidized MWCNT compared to pristine MWCNT. 

Krauel, K., Davies, N. M., Hook, S., and Rades,T. (2005), Using different structure types of microemulsions for the preparation of poly(alkylcyanoacrylate) nanoparticles by interfacial polymerization, J. Controlled Release, 106(1-2), 76-87. 

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