Stability of various doping species in trans-polyacetylene
Polyacetylene, a simple conjugated organic polymer, a material of strong interest if doped by various chemical species such as iodine or antimony pentafluoride : its electrical conductivity increases by more than twelve orders of magnitude. By increasing the dopant concentration one obtains a semiconductive or a metallic regime. Such properties allow us to make electronic material and then devices by convenient n or p type doping of polyacetylene. However,it is necessary to determine the thermal stability of the various dopant species. In this paper, we compared the stability of iodine, SbF5 and CF3SO3H dopants by studying the mass loss and the electrical conductivity decrease at various temperatures from 20‡C up to 180‡C. It is shown that only SbF5 is a relatively stable dopant up to 80‡C, a temperature which may be reached in some active electronic devices. Raman spectroscopy allowed us to measure the ratio of I−3 to I−5 ions during the desorption process and to propose a possible chemical reaction which produces gaseous iodine from the active dopant species.