Kinetics of chemical n-doping of polyacetylene

Abstract

Polyacetylene (PA) films were doped with tetrahydrofuran and benzene solutions of organo potassium and lithium compounds. The kinetics for doping were determined from the variation of the dopant concentration with time, as a function of film thickness, dopant concentration and doping temperature. The experimental doping rates were compared to computed values deduced from a doping model taking into account the interfibrillar diffusion, separately measured with an inert hydrocarbon. This comparison allows a minimum value (10 −15 cm 2/s) to be determined for the intrafibrillar diffusion coefficient D f of doped sites and cations. With such a value no homogeneous doping can be carried out at intermediate doping levels, for films thicker than about 50 microns, by a simple control of doping time or dopant concentration. This may, however, be achieved by a thermodynamic control using dopants of suitable redox potential.