Pulsed plasma synthesis of electrically conductive films of polypyrrole for potential use as environmental sensors

Environmental monitoring of gas phase contaminants is an important activity at the present time. Such monitors are required for general air quality measurements in many settings. The present thesis examines the possibility of creating a solid state sensor using a novel plasma polymerization approach to the synthesis conducting polymer films as the sensing element.; In contrast to prior CW plasma polymerization studies of pyrrole, the present investigation centers on pulsed plasma polymerization. In particular, this investigation examined the use of low duty cycle pulsed plasmas as a route to synthesis of relatively linear polypyrrole molecules of the type required for good conductivity. Such films can be contrasted with the relatively highly cross-linked structures normally obtained under CW plasma conditions.; The results obtained are indicative of forming progressiveiy more highly organized (i.e., less randomly cross-linked) structures as the radio frequency (RF) power is decreased during the polymerization process, as revealed by Fourier Transform Infrared Analysis of the polymer film. These spectra also reveal clearly that films deposited under the pulsed conditions exhibit a higher level of aromatic ring content.; Peak conductivity values of {dollar}{lcub}sim{rcub}10sp{lcub}-2{rcub}{dollar} S/m (10{dollar}sp{lcub}-4{rcub}{dollar} S/cm) were obtained. These values are significantly higher than literature values reported for other plasma synthesized conductive films. The pulsed technique provides an unique opportunity to synthesize these films under very low average power input conditions while still providing reasonable deposition rates.; The second major objective of the present study was to examine the possibility of utilizing conductive polymer films obtained by this technique for environmental sensing applications. This was achieved by contrasting the conductivity of polypyrrole films in the presence and absence of moisture and ammonia molecules.