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Abstract
We have investigated the possibility of obtaining the conducting form of polyaniline (PANI) using a one-step preparation route. The polyaniline is chemically synthesized in presence of either 1,5-naphtalene disulfonic acid (NDSA) as a dopant or the couple 1,5-naphtalene disulfonic acid as a dopant and the chromotropic salt as a co-dopant (NDSA-Chromo). We present here the study of the spectroscopic, structural and electronic properties of the obtained salts of PANI.
During this primary doping of PANI, only a single protonation by NDSA occurred. A co-protonation by HSO4 − appeared impossible in the presence of an organic disulfonic acid of strong acidity. This conclusion was confirmed not only by the elemental analysis but also by FTIR. The spectroscopic studies (UV-Visible-NIR) showed localization of the charge carriers (polaron) in the synthesized PANI.
Using this strategy, we hoped that each NDSA molecule might protonate two PANI amine sites to form a hierarchically ordered supramolecular structure. The obtained compounds show only a limited degree of crystallinity which is however sufficient to propose a possible structural organization. The adjunction of the co-dopant does not modify the local structure of the conducting material and conductivities in the 0.1 S/cm range are obtained for samples with partial doping level.
Further improvements in processing can be achieved in particular by using different solvents for obtaining films. In this respect, further progress is possible and this preparation path is worth to be explored in the future.
Acknowledgments
R. Borsali, R. Auzely, I. Pignot-Paintrand and Christophe Travelet from CERMAV laboratory in Grenoble are gratefully acknowledged for their advice and for permitting N. Naar to have access to additional techniques of investigation.