Comparison of different synthetic routes for sulphonation of polyaniline

Polyanilines containing sulphonic groups covalently bonded to the back bone were synthesized from parent polyaniline via sulphonation of the polymer utilizing differing sulphonation agents and differing means. The sulphonation conditions were studied as a function of several parameters including sulphonation time, starting forms of the precursor polymer, presence of oxidizer [(NH4)2S2O8] and temperature. The sulphonated polyanilines were characterized by FTi.r., elemental analyses, d.c. conductivity and electrochemical methods. It was found that using fuming sulphuric acid as the sulphonation agent gave both higher conductivity and higher sulphonation level for sulphonated polyaniline than implementation of other sulphonation agents and means.