Synthesis and characterization of water soluble polypyrrole doped with functional dopants

Several soluble polypyrroles (Ppys) in organic solvents were prepared using functional dopants [di(2-ethylhexyl) sulfosuccinic acid sodium salt (NaDEHS), butylnaphthalene sulfonic acid sodium salt (NaBNS), or dodecylbenzene sulfonic acid sodium salt (NaDBSA)] as previously described, and the resulting soluble Ppys were treated with chlorosulfonic acid to provide chlorosulfonyl (–SO 2Cl) group functionalized Ppys. Subsequent treatment of these polymers with hot water yielded sulfonic acid (SO 3H)-bearing water soluble polypyrroles [Ppy(SO 3H)–DEHS, Ppy(SO 3H)–BNS, Ppy(SO 3H)–DBSA]. The extent of sulfonylation was verified by FT-IR spectroscopy and elemental analysis and was proportional to the solubilities of the precursor polymers in organic solvent. Out of the series, Ppy(SO 3H)–DEHS powder showed the highest solubility (∼4% (w/v)) in water and film conductivity of ∼5×10 −1 S/cm. The charge carrier mechanism in accordance with the temperature change followed the typical 3D VRH model by σ= σ 0 exp[−( T 0/ T) 1/ n+1 ] formula, the VRH model of Mott. The sulfonic acid derivatized water soluble Ppy films showed reasonable thermal stability up to ∼180 °C as tested by TGA, and chemical stability in a wide range of pH.