Estimation of the rate of electron transfers between two contacting polymer surfaces

A bilayer of redox polymer films, Pt/poly-Os(bpy)2(vpy)2(2+)/polyRu(vbpy)3(2+), is coated on a Pt electrode. Reduction of the poly-Ru(3+) outer film of a pre-oxidized bilayer, Pt/poly-Os(3+)/poly-Ru(3+) is controlled by the rate of electron diffusion through the inner, polyOs(2+)/(3+) film. When oxidizing the outer poly-Ru(2+) film of a reduced Pt/poly-Os(2+)/poly-Ru(2+) bilayer, however, the rate of oxidation depends largely on the kinetics of electron transfer between the ca. monolayer of poly-Os(3+) and poly-Ru(2+) sites in contact at the interface between the two polymer films. The electron diffusion kinetics in the two polymer films perturb the interfacial reaction rate only slightly, so that a lower limit to the interfacial electron transfer rate constant is available.