Aqueous systems versus nonaqueous

Tab. 2 Potentials of zero charge ( pzc) for pc-Au electrode in contact with selected nonaqueous solvent-electrolyte systems. The pzc for pc-Au IH2O is equal to 0.20 V versus aqueous standard hydrogen electrode (SHE) and 0.85 V versus bis(biphenyl)chromium(l)/(0) redox couple (BBCr) [4]...

The hrst successful attempt to deposit conducting polymers using the feedback mode of the SECM was reported by Heinze and coworkers (28). The system has subsequently been refined (39). The essence of their method was to take advantage of the different solubility properties of the monomer versus the polymer in different solvents. The monomer was 2,5-bis(l-methyl-pyrrol-2yl)-thiophene (NSN) (Fig. 18), which is very soluble in organic solvents but insoluble in aqueous solutions. On the other hand, the respective polymer is insoluble in either aqueous or nonaqueous solutions. 

Polythiophene is readily produced by inserting a working electrode, counterelectrode, and reference electrode into a nonaqueous electrolyte in which 0.1 to 1.0 M thiophene is dissolved and then increasing the cell potential to greater than 1.6 V (versus SCE). Salts such as lithium or tetrabutylammonium perchlorate, hexafluo-rophosphate, or trifluoromethylsulfonate are typical electrolytes. Acetonitrile, ben-zonitrile, dichloromethane, and tetrahydrofuran are suitable solvents. As previously discussed for polypyrrole, polythiophene has been prepared in aqueous solutions [247]. A conductive, electroactive poly thiophene film was polymerized from a phosphoric acid-water-thiophene system using mild electrochemical polymerization conditions. 

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