DIFFUSION-COEFFICIENTS OF INTRINSICALLY ELECTROACTIVE POLYELECTROLYTES AND OF COUNTERIONS BOUND TO THEM

An electroactive label was attached to poly(acrylic acid) (molecular w eight = 5000) by reaction with ferrocenylethanol. The resulting ferroc ene label was stable when the polymer was dissolved in aqueous solutio ns, and the diffusion coefficient of the labeled polymer was estimated from the currents obtained as the ferrocene was oxidized at a rotatin g disk electrode. Although strong adsorption of the polymer on the ele ctrode surfaces depressed the oxidation currents below the convection- diffusion controlled values at rotating disk electrodes, it was still possible to estimate diffusion coefficients by appropriate analysis of the rotation rate dependences of the measured currents. At pH values where the labeled polymer became a polyanion, its diffusion coefficien t was also estimated from the reduction currents for Ru(NH3)(6)(3+) or Co(NH3)(6)(3+) counterions bound electrostatically to the polyelectro lyte. Good agreement was obtained between the diffusion coefficients e stimated by the two independent routes.