Influence of dopant ion and synthesis variables on mechanical properties of polypyrrole films

Abstract

Oxidized, conductive poly(pyrrolylium anion) films [poly(pyrrolylium) = PP⁺ where there exists about one cation per three pyrrole rings] have been prepared electrochemically in an effort to study the effect of counteranion structure and preparation conditions on the composition, order (crystallinity), and mechanical properties of the films. The counteranion principally employed was p‐toluene‐sulfonate (OTs⁻), although benzenesulfonate (BZs⁻), p‐ethylbenzene‐sulfonate (EBs⁻), and p‐dodecylbenzenesulfonate (DBs⁻) were incorporated in several polypyrrole films. It was found that the amount of OTs⁻ incorporated increased with increasing potential during synthesis, suggesting a parallel increase in the extent of oxidation of the polymer. Mechanical testing of the same films demonstrated that the ultimate tensile strength decreased as the electrode potential and current density during synthesis increased. X‐ray diffraction indicated that the degree of order (reflected by the widths of the diffraction lines), albeit quite small, is dependent upon the anion species and synthesis conditions. Interestingly, samples with the highest degree of order exhibit the highest electrical conductivities.