EDOT monomers solubility

Since the EDOT monomer is not soluble in water, its reaction with the oxidant, FeCls in water is inhomogeneous. As a result, in a rapidly mixed reaction, the polymerization occurs around EDOT droplets at the EDOT-water interface forming hollow capsule-like structures, such as the one shown in Figure 7.53. 

While a lot of literatures concerning conducting polymer nanoparticle were published, there were limited reports on the fabrication of PEDOT nanoparticle due to the relatively low solubility of the 3,4-ethylenedioxythiophene (EDOT) monomer in aqueous media. Several synthetic methods for the PEDOT nanoparticle have been reported using seed polymerization, emulsion polymerization and dispersion polymerization. 

Another approach has been performed for preparation of PEDOT-coated silica core-shell particles and PEDOT hollow particles [360]. Silica particle size of 130 nm was utilized as the core seed and p-TSA was used as a good dopant. p-TSA played a role of improving the solubility of EDOT monomer... 

Recently, PEDOT nanomaterials have been fabricated in the shape of rods, tubes, thimbles, and belts through chemical polymerization in the pore of AAO membrane [368]. EDOT-fiUed AAO membrane was employed to overcome the poor solubility of EDOT monomer in water and the difficulty in controlling the reaction time. Chemical polymerization has been accom-pUshed by transferring EDOT-fiUed AAO membrane into an aqueous oxidant solution. EDOT monomer was retained in the pore of the AAO due to the extremely low solubility of EDOT in the aqueous solution. The elevated polymerization temperature and high concentrated FeCb solution increased the rate of polymerization, which resulted in the augment of wall thickness. Under these conditions, different nanostructures of PEDOT such as belt-like structure, thimble-like structure and nanorod were reaUzed by different FeCU concentration and polymerization temperatures. 

The industrially useful PEDOT PSS is made by aqueous oxidative polymerization of the EDOT monomer in the presence of the template polymer PSS. PSS is a commercially available, water-soluble polymer and can serve as a good dispersant for aqueous PEDOT. Polymerization with the oxidant sodium peroxodisulfate yields the PEDOT PSS complex in a conductive, cationic form (Figure 14.2). 

The heterocyclic monomers, i.e., pyrrole, aniline and 3, 4-ethylenedioxythiophene (EDOT], with oxidation potentials lower than that of water decomposition can be electrochemically polymerized in aqueous media. However, the solubility of aromatic... 

The research on PTh derivatives has, in recent years, been strongly oriented to exploiting the very appealing properties of 3,4-ethylenedioxythiophene (EDOT) the presence of two oxygen atoms directly connected to a single Th unit allows this monomer to be oxidized at particularly low potential values. Furthermore, the condensed ring confers the monomer a polarity suitable to make it soluble enough... 

The oxidative polymerization with the aid of persulfate in water is limited to EDOT and a few derivatives, which are water-soluble to a certain extent (for example, EDOT-CH3, EDOT-CH2OH, sulfonate-modified EDOT or oligo-ethylenglycol-substituted EDOT). In contrast, the in situ polymerization is of far broader range with respect to the EDOT derivatives applicable. The minimum prerequisite is a moderate to good solubility in alcohols like ethanol or n-butanol at slightly elevated or room temperature. Another important aspect is the reactivity of the monomer, which must not be too high with iron-III toluenesulfonates to avoid instantaneous polymerization. 

The solvent of choice for the synthesis of PEDOTPSS complex is water. Water is inert with respect to most oxidation or reducing agents. It is highly polar and a good solvent for PSS. However, water is a poor solvent for the monomer EDOT. At 20°C 0.21g of EDOT can be dissolved in 100 mL water. The solubility increases in the presence of PSS to 0.30% as shown in Figure 9.3. Furthermore, the figure shows that solubility of EDOT in the presence of PSS increases with temperature. In order to overcome the limited solubility, Lefebvre et al. have used mixtures of water and acetonitrile to increase the solubility of EDOT. ... 

A key factor for the formation of dense outer polymer layers is the concentration of the monomer. At low concentrations the polymer formation is limited by diffusion, which results in inhomogeneous porous layers. Since the solubility of EDOT in water, which is the favored solvent for industrial applications, is very low, outer layer formation with EDOT is hindered. Sufficiently high concentrations of EDOT in water to grow a dense polymer layer can be realized by forming microemulsions through the use of surfactants. - ... 

In the presence of acid the manganese dioxide reduces to soluble manganese(II) and simultaneously polymerizes the monomer EDOT to the conductive polymer PEDOT. The acid anions serve as charge-balancing counterions and get incorporated into the polymer. The chemical nature of the acid employed will influence the nucleation and the crystallization of the polymer. Morphology and achievable conductivity of the resulting polymer will therefore be critically influenced by the acid involved. ... 

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