Properties of electropolymerized high density polypyrrole films

The high density PPy films (HD-PPy, ρ > 1.4 g/cm³) doped with p-toluenesulfonate (TOS^-) counterions were electropolymerized by a facile approach in H₂O and acetonitrile (AN) mixed solvent. The structure and electrochemical properties of the HD-PPy films were measured by X-ray photoelectron spectroscopy (XPS), thermogravimetric (TG) analysis, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results show that appropriate ratio of AN/H₂O (99/1) could be favorable to increase the density of PPy films. Further enhancement of the density could be obtained by using higher current density (such as 10 mA/cm²), as it favors the formation of two-dimensional structure. Generally, low temperature of polymerization, T (e.g. -20°C), is advantageous to the enhancement of density and conductance of PPy films. But if T_p is too low, it becomes disadvantageous in case of the high current density of polymerization. The HD-PPy films (1.42 g/cm³) were obtained at 0°C with 10 mA/cm² in AN/H₂O(99/1) solution. Furthermore, HD-PPy films were characterized not only by high electronic conductivity (∼220 S/cm) and high thermal stability, but also by low electrochemical activity. It was indicated that the HD-PPy would be not only an excellent electrode material but also a promising corrosion protection material.