Electrical resistivity and magnetoresistivity of protonic acid (H2SO4 and HCI)-doped polyaniline at low temperature

Electrical-transport properties of protonic acid (H2SO4 and HCl)-doped poly aniline (PANI) in an aqueous ethanol medium were investigated in the temper ature range 1.8 K less than or equal to T less than or equal to 300 K and i n a magnetic field up to 8 T. The room-temperature resistivity of HCl-doped PANI is larger than that of H2SO4-doped PANI. The resistivity ratios rho(r ) = rho(1.8 K)/rho(300 K) of the samples are high. The samples in the insul ating region show a crossover from a Mott to an Efros-Shklovskii variable r ange hopping conduction at T = 9.8 K for H2SO4-doped PANI and 8.5 K for HCl -doped PANI. The magnetoresistivity of these samples is also explained by t he variable range hopping theory. The different physical parameters were ca lculated from the experimental data. (C) 2000 John Wiley & Sons, Inc.