Monomers solubilized

Based on the Smith-Ewart theory, the number of latex particles formed and the rate of polymerization in Interval II is proportional with the 0,6 power of the emulsifier concentration. This relation was also observed experimentally for the emulsion polymerization of styrene by Bartholomeet al. [51], Dunn and Al-Shahib [52] demonstrated that when the concentrations of the different emulsifiers were selected so that the micellar concentrations were equal, the same number of particles having the same size could be obtained by the same polymerization rates in Interval II in the existence of different emulsifiers [52], The number of micelles formed initially in the polymerization medium increases with the increasing emulsifier concentration. This leads to an increase in the total amount of monomer solubilized by micelles. However, the number of emulsifier molecules in one micelle is constant for a certain type of emulsifier and does not change with the emulsifier concentration. The monomer is distributed into more micelles and thus, the... 

Nanogels made up of various intramolecularly cross-linked macromolecules have been prepared simply by performing the polymerization of hydrophilic monomers solubilized in the micellar core of reversed micelles, and they represent distinct macromolecular species from those obtained in bulk [191,240]. 

As shown in Fig. 6, the amount of polymerized monomer droplets strongly depends on the emulsifier concentration. With increasing emulsifier concentration, the amount of monomer initially present in the monomer droplets decreases in favor of monomer solubilized in micelles. Concurrently the fraction of polymerized monomer droplets decreases and more microgels are formed. Above a certain emulsifier concentration which is about 0.8 mol/1 in thermal initiation, the monomer is completely solubilized prior to polymerization and no polymerized monomer droplets are formed. 

Fig. 14. Monomer placement in particles during emulsion polymerization, a, b, c, Various stages of polymerization (see text) d monomer particle stabilized by emulsifier diam. = 104 nm e monomer-polymer particle f, monomer solubilized in a micelle q, emulsifier. See p. 180 of ref. 126.

Before polymerization starts there will thus be some monomer solubilized inside the micelles, more monomer in soap covered large droplets, and perhaps a small amount of monomer in true solution in the water. Emulsifier will also be located in the micelles, in aqueous solution, and on the surfaces of the monomer droplets. Most of this soap will be located in the micelles. The concentrations of... 

On mixing this emulsifier solution with an only slightly water-soluble monomer, a small fraction of the monomer solubilizes in the micelles—i.e., some monomer dissolves in the hydrocarbon interior of the micelles, which swell to roughly double their original size. The remainder of the monomer is dispersed in small droplets, the size of which depends on the intensity of agitation. The diameter of these droplets is usually not smaller than about 1 micron (10,000 A.) and, hence, there are at most some 10 droplets per milliliter of water at the normally employed ratio of monomer to water phase. 

Polymerizations performed with an emulsifier above its critical micelle concentration with all the monomer solubilized within the micelles and without any monomer present as emulsion droplets may be described as micellar polymerizations [62]. Although such systems can never produce a high yield of polymer per unit volume they are advantageous if it is desired to use photochemical initiation, these being transparent whereas emulsions are opaque. Micellar polymerizations can help to elucidate the mechanism of emulsion polymerizations. They are useful practically when it is desired to copolymerize hydrophilic and hydrophobic monomers to synthesize associative thickeners [63,64]. 

Thermal decomposition of initiator molecules produces pairs of radicals which are very likely to recombine when produced within the small volume of a latex particle or of monomer solubilized within a micelle. But if one radical escapes to the aqueous phase, a single radical is left in an isolated locus which is the prerequisite for emulsion polymerization. This still seems the most probable reason... 

However, the preparation of latex particles may be perceived as having reached a level at which the potential for a fundamental breakthrough in the final materials per se is rather limited. Pioneering efforts may instead be expected in the development of polymeric microcompartmentalized materials. This development, in a limited form, may be exemplified by the work of Gan and colleagues [28], who polymerized organic monomers solubilized in bicontinuous microemulsions and obtained microporous organic polymers. This area is, of course, of future interest, but the problem of lack of correlation between the microemulsion colloidal structure and the microstructure of the final material may result in a focus on the polymerization of liquid crystalline material where even complex systems [29,30] have been shown to retain their microstructure after polymerization. This area of polymerization has been further developed and systematized by Antonietti [31,32], Antonietti et al. [33], and Fendler [34]. 

Commercial electropainting only dates from the early 1960s and the first processes to be introduced used anodic deposition. Some typical paint formulations would contain (i) polycarboxylic acids based on acrylic acid as monomer solubilized by an organic amine, (ii) alkyds, i.e. branched polyesters based on naturally occurring long-chain carboxylic acids and polyalcohols, e.g. glycerol, and (iii) epoxy resins based on phenols, e.g. 

In cases where there is little affinity of the polymer for water, as for polystyrenes or polyalkylacrylates and methacrylates, little effect of surfactant on water solubihty would be expected. The action of the surfactant on such latex systems is then limited to its action as a monomer solubilizer during preparation and an adsorbed stabilizer afterward. 

Depending on the nature of used material in fibrous implantable medical device design, degradation products take different forms. As previously described, polymer degradation usually results in monomer solubilization. Degradation of metallic material occurs by metal ions released at exposed weak surfaces of the material. Moreover, degradation of material in the biological environment may happen at the structural level and be associated with debris and particle release. 

It may be noted that many of the ingredients are multifunctional. For example the soap serves to emulsify the monomers, solubilize the monomers in the micelles and to stabilize the latex particles formed. The mercaptan is not only a chain transfer agent but also a promoter of polymerization in the case of the hot rubber. 

At subsaturation conditions, the rate is proportional to the 0.4th power of the emulsifier concentration which deviates slightly from the micellar predictions. This behavior is attributed to the monomer-solubilization role of the emulsifier layer zone. 

Polymer (latexes) dispersions are generated by the radical polymerization of unsaturated monomers solubilized in the micellar systems. The significant growth in the production of these latexes is due to a number of factors such as ... 

In polymers that have very little affinity for water, such as for polystyrene or alkyl acrylates and methacrylates, little effect of surfactant on water solubility would be expected. The action of surfactants in such latex systems would be limited to their action as monomer solubilizers during preparation and as adsorbed stabilizers afterward. 

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