A First Principle Analysis of the Structure of Oligoanilines Doped with Alkylsulfonic Acids

The interaction of polyaniline with alkylsulfonate dopants have been investigated at the atomic level using quantum mechanical methods. Calculations have been performed on complexes formed by dopant molecules with an alkyl group ranging from methyl to nonyl and model oligoanilines of different sizes. The stabilization provided by the formation of the alkylsulfonate center dot center dot center dot oligoaniline complexes (70-90 kcal/mol) is significantly higher than that found for conventional hydrogen bonds (5-12 kcal/mol) but lower than that obtained for methylsulfate center dot center dot center dot alkylammonium and methylsulfate center dot center dot center dot Na+ systems (120-135 kcal/mol). On the other hand, the influence of size of the alkyl group contained in the dopant oil the interaction is practically negligible, whereas, in opposition, the number of aniline units used to represent polyaniline significantly affects the energetics of the interaction. Specifically, the interaction energy of ail alkyl-dopant molecule and an infinite polyaniline chain has been predicted to be around -65 kcal/mol. The overall results allow the conclusion that the interaction between alkylsulfonate dopants and polyaniline is a very local phenomenon.