Comparative studies on diffusion behaviour of electrochemically prepared polythiophene and polypyrrole: effect of ionic size of dopant

In this paper, the diffusion measurements into and out of electrochemically prepared polythiophene films have been studied in electrochemical cells containing N(Bu)4BF4, NaClO4, LiAsF6 and NaSbF6 in propylene carbonate and the effect of the size of the diffusing ions on diffusion coefficients have been discussed. The diffusion behaviour of BF4− ions into and out of electrochemically prepared polypyrrole has also been studied for comparison. An increase in diffusion coefficients in the order of NaSbF6<N(Bu)4BF4<NaClO4<LiAsF6 at 273 K has been observed. It is proposed that the ionic size is a limiting factor. These results are discussed in terms of potential applications of these polymers.