INTERDIGITATED ARRAY ELECTRODE DIFFUSION MEASUREMENTS IN DONOR-ACCEPTOR SOLUTIONS IN POLYETHER ELECTROLYTE SOLVENTS

A steady-state interdigitated array (IDA) electrode method is introduced for measurement of the diffusivity of charge in mixed-valent donor/acceptor solutions in polyether solvents. The method is based on establishment of steady-state crossed concentration gradients of donor and acceptor solutes in the 15-mu-m gap between the IDA finger electrodes. Apparent diffusion coefficients D(APP) are determined for the couples [Cp2Fe]+/0, [Cp2*Fe]+/0, TMPD+/0, TCNQ0/-, and DDQ0/- in poly(ethylene glycol dimethyl ether) (MW = 400 and 1000) with lithium perchlorate electrolyte. The D(app) values are in the range 10(-10)-10(-6) cm2/s and exhibit strong variations with solute concentration. The changes are interpreted in terms of the concentration dependencies of the solute physical coefficient D(PHYS) and of the electron self-exchange reactions between donor and acceptor. The IDA D(APP) measurements can also be employed to track the crystallization kinetics of the polyether solutions.