Synthesis and Deposition of Conductive Polymers with the aid of Ionic Liquids
Ionic liquids are suitable for the synthesis of conductive polymers, since they have a wide electrochemical window which ensures their excellent oxidative and reductive stability. This capability made them more popular in recent years than the conventional molecular solvents and electrolytes.
Conductive polymers such as polypyrrole, polythiophene, polyaniline etc. are organic polymers that conduct electricity, and are used as a replacement for silicon in a range of applications. These polymers can be easily synthesized by polymerization of monomers in the presence of molten salt. Since they have conjugated systems of electrons, they can be either reduced or oxidized by chemical or electrochemical processes. Their most popular applications include organic electronics, organic light emitting diodes (OLEDS), organic polymer solar cells (OPVS), fuel cells, etc.
A polymer that has drawn attention due to its wide range of applications (conductor, electrode, and semiconductor) during the last few years is Polythiophene (Pth). It is usually synthesized by electrochemical oxidation of the thiophene monomer in an organic solution. Ionic liquids are excellent solvents for many organic compounds and 1-butyl-3-methylimidazoliumhexafluoro-phosphate ([BMIM]PF6) ionic liquid was reported to be an excellent solvent for Polythiophene (electrochemical synthesis of Pth).
Ionic liquids can also be used as a media for the electrochemical deposition of conducting polymers onto surfaces to produce, for example, electrochromic films for electronic display devices. Polypyrrole (Ppy) is considered to be suitable for such electrochromic applications. By applying a relatively high potential, the polymer can be deposited onto a metallic surface such as iron, without any significant overoxidation problems compared to the use of other depositing media.