Films obtained by plasma polymerization of pyrrole

This work presents the synthesis by plasma and characterization by IR, SEM, thermogravimetry and electric conductivity of polypyrrole films, both undoped and doped in-situ with iodine, The synthesis was carried out in a vacuum glass reactor with reaction times from 60 to 300 min. The plasma was produced by electric glow discharges with a resistive coupling mechanism at 13.5 MHz. The films were obtained with thickness between 2.7-13.1 mu m at a rate of 45.2 nm/min and conductivity between 10(-12)-10(-9) S/cm. The thickness of the films doped with iodine was between 4.9-19.8 mu m at a rate of 64.4 nm/min and conductivity between 10(-9)-10(-3) S/cm, The electric conductivity of polypyrrole was studied as a function of its reaction time and the environmental moisture. Electron microscopy analysis and thermal decomposition were also studied to observe the morphology and the thermal stability in the films. The electric properties showed a strong dependence on the moisture, in which two regions were clearly observed. The first region predominated up to 70% of relative humidity. In this region moisture had no significant influence on the conductivity. In the second region, at more than 70% of relative humidity, moisture increased the conductivity by several orders of magnitude. (C) 1999 Elsevier Science S.A. All rights reserved.