INFLUENCE OF BROMINE DOPING ON THE ELECTRICAL-CONDUCTIVITY OF CARBONIZED POLY(VINYLIDENE CHLORIDE)

The electrical conductivity of carbonized poly(vinylidene chloride) (PVDC) was found to increase by doping with bromine, and the relative increases were higher for carbons prepared at lower temperatures. An X-ray photoelectron spectroscopy (XPS) study revealed that bromine dopants took three states: one covalently bonded state and two ionized states. A thermogravimetry study supported the existence of at least two states of the bromine dopants. Examination of specimens with different bromine contents prepared by alteration of the pressure and periods of doping and by thermal or vacuum elimination showed that (1) the doping and undoping processes are irreversible and (2) the bromine species that cause the increase in electrical conductivity are the ionized species (Br3- and Br-). The change in the electrical conductivity is explained by an electron transfer to bromine from a semiconductor phase coupled with the three-phase model previously proposed. © 1990 American Chemical Society.