Electrochemical properties of self-assembled monolayers of polyaniline: effects of the thiol substituent and reduced dimensionality.

Self-assembled monolayers and bulk films of thioanilines, polymerized on gold and platinum surfaces, have been characterized and compared to bulk polyaniline (PANI) films. In a previous study [Kuwabata; et al. Langmuir 1999, 15, 6807-6812], only one redox couple was observed in the cyclic voltammetric profile of a polymerized monolayer of thioaniline on gold, in contrast to the known profiles of bulk PANI, which exhibit two couples. We observe two couples in both a polymerized thioaniline monolayer and a bulk polythioaniline (S-PANI) film, but the 200 mV window between the couples (the width of the region of high conductivity) in the S-PANI films is much smaller than the 600 mV window in bulk PANI. We ascribe this difference to the presence of the thiol substituent. The windows of high conductivity of the polymerized thioaniline monolayer and the bulk S-PANI film are the same within the limits of our experiment, implying that the difference in the dimensionality of the films (a 2D monolayer vs 3D bulk films) has a limited effect on the films' voltammetric profiles.