Effect of aqueous and organic solvent ratio on the electropolymerization of bithiophene in the mixed solutions

The use of suitable ratio of water to acetonitrile could lower the onset oxidation potential of bithiophene to about 0.6 V vs. Ag/AgCl in the aqueous/organic mixed solution. This means that bithiophene can be electropolymerised at very low potential in such solutions, which is usually unachievable in pure organic media. When the current density for electropolymerisation was kept constant as 1.0 mA/cm2, the electropolymerization potentials for bithiophene could be tuned to stable values of 0.8, 0.9, and 0.94 V by keeping the volume ratio of water to acetonitrile as 2:1, 1:1, and 1:4, respectively in the mixed solution. Evidence shows that the chemical structure of polybithiophene synthesised by this technique is very similar to that of the polymer formed in organic media. The volume ratio of water to acetonitrile has a significant effect on electropolymerization of bithiophene as well as on the electrochemical properties and morphology of the polybithiophene films.