Monomer role electrolyte

All these results should convince us that the monomer plays a crucial role in the phase diagrams of these systems. In fact, this role, more or less ignored by formulators until recently, is two-fold. As a cosurfactant, the monomer increases flexibility of the interfacial film. It can therefore deform more easily to produce a sponge structure. And as an electrolyte, the monomer reduces aqueous solubility of ethoxylated surfactants. It thereby favours their gradual transfer into the organic phase and the formation of a bicontinuous structure. This effect of salt in the formation of bicontinuous microemulsions is well known to the users of such systems. It is significant in this respect that the same systems without monomer or electrolyte (if the monomer is neutral) do not lead to bicontinuous structures. 

In summary, these results show that the role of the monomer is twofold as a cosurfactant, it increases the flexibility and the fluidity of the interface, which favors the formation of a bicontinuous microemulsion. An an electrolyte, it induces the latter structure. These two conditions are imperative. Similar water-oil-surfactant (s) systems do not lead to bicontinuous microemulsions in the absence of monomers or salts (when the monomer is not itself an electrolyte). 

Other areas of technology where the transport of small molecules through polymers plays a key role include foams (where small molecules are used as blowing agents for foam expansion [9-11] and any gas trapped in the cells of a closed-cell foam affects key properties such as the thermal conductivity [12]), plasticization [13,14], removal of process solvents, residual monomers or other impurities by techniques such as supercritical fluid extraction [15,16], biosensors, drug implants, and polymer electrolytes (where the penetrants are ionic). 

It is obvious that the distinction among these fields cannot be made until the mechanism of the electrodic events is completely understood, and the eventual role played by all the species present in the electrolytic medium is carefully investigated. In many cases some of these species have been discovered as being responsible of the initiation, but, on the contrary, sometimes a deeper insight in the process has led to the conclusion that the monomer is the direct electrodic depolarizer4,5 ... 

This reaction seems to be specific for monomers containing amide groups (acrylamide or methacrylamide), but once these monomers are present in the electrolytic medium, other monomers, e. g., acrylonitrile, can be polymerized. The authors attribute the polymerization initiation to the electrogenerated metal ions only, but it is possible that even the perchlorate ion plays a role in the formation of the initiating species. The polyacrylamide thus obtained has an electrical conductivity 3 to 4 times higher than that of polymers obtained by the usual methods. This is due to the presence of metallic cations coordinatively bound in the polymer bulk. The presence of these cations increases the thermal stability of the polymer by 20—40%. 

Electrochemical polymerization results in the synthesis of a thin film on the electrode that is used for further electrochemical and optical characterization. Since this process is very simple and all the standard electrochemical studies can be carried out using minimum amounts of monomer, this is a method of choice when the final polymer is insoluble or the monomer synthesis is tedious or expensive. The solvent for electropolymerization is chosen in such a way that the monomer is soluble, whereas the polymer is insoluble. The electrode surface, nature of the electrolyte and other polymerization conditions play a significant role in the morphology of the polymeric film. It is possible to synthesize various nanostructures including nanofibers, nanodots, nanonetwork, and nano- to microsize tubes of functionalized PEDOTs and PProDOTs. Oxy-thiophenes can be electropolymerized more easily due to their low oxidation potential as compared to alkylthiophenes. ... 

On some occasions the electrolyte plays a decisive role in obtaining polypyrrole in non-inert substrates. This is the case of Fe, for which in aqueous solution only nitrate anions give polypyrrole deposits [97]. This behaviour has been correlated with the tenancy of the nitrate ion to yield radicals at the anode, initiating a radical oxidation of the monomer. In the same way, good-quality PPy films on aluminium in aqueous solutions are only obtained from acid electrolytes [94]. 

Electrosynthesis is based on the use of an electrochemical cell and a requisite for this technique is the use of electroactive moleeules, for example thiophene, pyrrole and aniline among organic monomers. The experimental setup is based on a galvanic cell, a potent ostat and two electrodes [206], as schematized in Fig. 1.18. The monomer is solubilized typically into organic solvents or in aqueous media and usually an electrolyte (e.g. lithium perchlorate or tetrabutylammonium acetate) is added. Platinum, carbon rods, magnesium, mercury, stainless steel can be used as electrodes and the electrosynthesis can be carried out with constant potential or constant current. The choice of the electrodic material, its shape and size play a cmcial role in many electrochemical reactions. 

In common practice the aqueous phase, or serum, of a polymer dispersion is only investigated for its pH (Sect 3.2.1). On the other hand, the aqueous phase contains a host of substances which play an important role in many applications. These substances include (a) emulsifiers, (b) initiator residues, (c) electrolytes from the neutralization process or from initiator decomposition (for example sodium sulfate from sodium peroxodisulfate), (d) unreacted water-soluble monomers such as acryHc add or vinyl sulfonic acid, and (e) water-soluble oligomers formed from this kind of monomers. 

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