Pressure—temperature-induced conductivity in polyaniline base and salts

The conductivities of polyaniline (and poly(2-methoxyaniline), poly(2-methylaniline)) and of the sulfonated derivative have been studied as a function of pressure (0 to 30 kbar) and of temperature (20 to 100–400 °C). Conductivity measurements were made with the aid of impedance spectroscopy in a piston—cylinder high-pressure cell. The conductivity of emeraldine chloride is quite stable up to 10 kbar and then increases continuously up to a factor 50 (1 to 60 S cm−1 at 100 °C, 25 kbar). Similar behaviour is observed for the ortho-substituted derivatives (poly(2-methylaniline) and poly(2-methoxyaniline)) as well as for the self-doped sulfonated polyaniline. The conductivity increases regularly with temperature and then drops irreversibly: highest values are observed at 90, 70 and 60 °C for the self-doped material and the chlorides, poly(2-methoxyaniline chloride) and poly(2-methylaniline chloride), respectively. A strong increasing in conductivity is observed versus temperature and pressure, up to 10−4 S cm−1, at 300 °C under 20 kbar for the emeraldine base. The nature of the charge carriers (electrons or protons) is discussed.