Abstract
In our previous work, we have reported that the electropolymerization of an immiscible monomer, such as 3,4-ethylenedioxythiophene (EDOT), proceeded very smoothly in acoustically emulsified solutions. In this study, we investigate the details of the reaction mechanism in order to apply this methodology to polymer and organic syntheses. It was found that the emulsions prepared by acoustic emulsification in aqueous solutions containing 1.0M Li_2SO_4, 1.0M LiNO_3 and 1.0M LiClO_4 respectively, were quite stable even after standing for 60min. In addition, these emulsions have the characteristic of giving narrow droplet size distributions in the manometer range. Above facts suggest that the characters of emulsion prepared by acoustic emulsification were not influenced by the electrolyte species. On the other hand, the polymerization of acoustically emulsified EDOT hardly occurred in 1.0M Li_2SO_4 and 1.0M LiNO_3 aqueous solutions. In sharp contrast, the polymerization proceeded very smoothly in 1.0M LiClO_4 aqueous solution. It is well-known that LiClO_4 is relatively soluble in an organic medium. LiClO_4 dissolved in the droplets should play the role of the supporting electrolyte and contribute to the formation of an electric bilayer inside the droplets. It can be consider that the very smooth polymerization of EDOT in an aqueous medium was ascribed to the formation of nanometer-size monomer droplets by acoustic emulsification and formation of electric bilayer inside the droplets by supporting electrolyte dissolved in droplets.
