Generation current of charged micelles in nonaqueous liquids: Measurements and simulations

Electrically charged species in nonaqueous media still hold many questions. Recent studies and applications show the need for a better understanding of the origin and nature of these charged species. Transient current measurements have been used to study the conductivity of nonaqueous liquid containing charged inverse micelles. At small time scales (1–100 ms) drift and diffusion of charged species are the main contributions to the measured current. At larger timescales (above 1 s) a nonzero quasi steady-state current at high voltages (above 0.5 V) remains. This indicates that besides drift and diffusion an additional process occurs. The dependence of the quasi steady-state current on the applied voltage, micelle concentration, and device thickness has been investigated. Experimental results have been compared to simulations and analytical calculations. It is concluded that the quasi steady-state current results from a bulk disproportionation reaction between neutral micelles that generates charged micelles. And therefore this technique allows for direct quantification of the reaction kinetics from which the charged species originate. Charged species in a nonaqueous medium with added surfactant have been found to originate from a disproportionation reaction between neutral inverse micelles that generate charged micelles.