Electrical conduction in sulfonated polystyrene films

Abstract

The d.c. electrical conductivity of 14% (by weight) sulfonated polystyrene films was measured as a function of temperature from 20° to 60°C in a 25-micron vacuum. Sulfonated films in the silver, cadmium, and methylene blue sorbed forms were prepared for these electrical measurements. Plots of log specific conductance versus reciprocal temperature gave straight lines with activation energies of 0.49 eV for methylene blue, 0.60 eV for Ag, and 0.98 eV for Cd. Large conductivity ansiotropies were also measured for the sulfonated polystyrene films in the Ag and methylene blue forms. Attempts with Hall-effect measurements to determine the sign and concentration of the charge carriers were unsuccessful. Photoconduction studies were also carried out with Ag-, Cd-, and methylene blue-doped sulfonated polystyrene films in the film lateral direction of highest photocurrent. Rise of photocurrent under d.c. illumination was found to be exponential with time constants of 29, 3.5, and 1.0 sec for Ag-, Cd-, and methylene blue-doped samples. The rise and decay of photocurrent in these films exhibited similar responses. Photocurrent was ohmic up to 400 V and varied linearly with light intensity up to 200 milliwatts.