Low pressure effect in the electrical conductivity of doped polypyrrole

We report the first data of the pressure dependence of the electrical conductivity of BF4−-doped polypyrrole below atmospheric pressure. The pressure dependence has characteristics of a phase transition and is interpreted as a conformational coil—rod transition. The time response of the conductivity to a sudden increase of pressure, the existence of a glass transition and the pressure dependence of the optical and IR spectra support this interpretation. The pressure effect should be considered in experiments with polypyrrole gas sensors.