AC plasma polymerization of pyrrole

An alternating current induced plasma generating assembly was constructed for simultaneous polymerization and doping of pyrrole with iodine. Thin films (0.3–2.7 µm) of 50 Hz AC-plasma polymerized polypyrrole and iodine-doped plasma polymerized polypyrrole were synthesized at 800–1500 V at an optimized reaction time of 30 min. The films were subsequently characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, and ultraviolet-visible spectrophotometry. Electrical conductivities of the films were measured by a two-point probe technique. Infrared spectroscopic analysis shows mainly characteristic polypyrrole peaks with some evidence that pyrrole rings may have been broken by the applied plasma discharge energy. This may have resulted in the loss of a small amount of nitrogen atoms from the rings as evidenced by a slightly lower nitrogen composition. The conductivity of the iodine-doped plasma-polymerized polypyrrole films is in the range of 10−6 to 10−7 S/cm. This is approximately 1 order of magnitude higher than those of undoped films from AC-plasma polymerization measured for comparison. Thorough analysis and discussion on the synthesis and properties of PPPy and PPPy/I2 is presented.