Effect of polymerization time on the humidity sensing properties of polypyrrole

In this paper, we prepared polypyrrole (PPY) films using a chemical method at different polymerization times. Their structure and morphology were characterized through X-Ray powder diffraction (XRD), IR, and scanning electron microscope (SEM). The humidity sensors were made by a coating membrane method. We studied the humidity sensing properties of the PPY-x films (the letter 'x' denotes the polymerization time and it was 4, 24, or 96 h). It was found that the humidity sensing properties of PPY could be improved greatly by extending the polymerization time. According to our experiment results, we predict that the humidity sensing properties of conducting polymers could be improved by increasing their crystallinity degree. (c) 2007 Elsevier B.V. All rights reserved.