Hw. Rhee et al., REDOX BEHAVIOR OF POLYPYRROLE FILMS IN DIFFERENT SOLVENTS, Molecular crystals and liquid crystals science and technology. Section A, Molecular crystals and liquid crystals, 227, 1993, pp. 207-218
The redox behavior of polypyrrole (PPy) films has been examined by mea
ns of cyclic voltammetry and SEM/EDS. PPy was galvanostatically prepar
ed in acetonitrile (AN) containing tetrabutylammonium dodecylsulfate (
TBADS) as an electrolyte. Charge compensation mechanism of PPy films w
hich incorporate dodecylsulfate (DS) ions was greatly influenced by th
e solvents or electrolyte used in the redox reaction. When the PPy was
switched between -0.8 V and 0.5 V in the TBADS/AN solution, bulky DS
ions were participated in the redox reaction of the swollen PPy film.
In the aqueous solution containing NaDS, on the other hand, Na cations
worked as main charge-compensating ions because DS anions with long a
lkyl chains were trapped in the contracted PPy and difficult to move d
uring the switching process. However, DS ions in the TBADS/water solut
ion should be the compensating ions to show higher oxidation potential
s. When the free-standing films were reduced for 24 hours at -0.8 V ag
ainst an Ag/AgCl reference electrode in the TBADS/AN solution, EDS sul
fur concentration profiles showed that DS anions were removed from the
films, which lead to a reduction in film thickness to two thirds of t
he original thickness but in the aqueous solutions there was no change
in film thickness upon reduction. The initial redox reaction in the T
BADS/AN solution was most reversible and reactive but long term cyclab
ility (electrochemical stability) of the PPy films in AN was inferior
to that in water, which resulted from the morphological collapse durin
g the repeated redox reaction.