Redox Properties of Phosphazene Polymers with Pendant Ferrocene Groups

The electrochemistry of a series of phosphazene polymers {[Ph(Me)=N] x[Ph{R′RC(OH)CH2}P=N]y}n where R′ is (η5C5H4)Fe(η5C5H5) with varying degrees of ferrocene substitution (3, x = 0.94, y = 0.06, R = H; 4, x = 0.80, y = 0.20, R = H; 5, x = 0.64, y = 0.36, R = CH3; 6, x = 0.56, y = 0.44, R = H) has been investigated in CH2Cl2 and as films evaporatively deposited on the electrode surface. The E½ of the ferrocene units (463 ± 12 mV vs Ag/AgCl) for the polymer dissolved in CH2Cl2 is essentially independent of the degree of substitution and background electrolyte. Diffusion coefficients (Do) for 3–6 were determined using a combination of rotating-disk voltammetry and chronocoulometry. A trend of increasing Do with increasing degree of ferrocene substitution suggests a dual mode of transport, where both physical diffusion and electron hopping are occurring. Polymer films were deposited by evaporation on Pt and glassy C electrodes, and E½ values were measured at 470 ± 10 mV (Ag/AgCl) when the films were immersed in 0.1 M TBAP, (TBA)PF6, TEAP, or (TEA)Br in acetonitrile or in TBAP or (TBA)PF6 in CH2C12. Film-casting parameters were found to influence polymer swelling and charge-transport numbers (Do½C, which vary with the degree of ferrocene substitution from 1 × 10−7 to 5 × 10−9 mol/(cm2 s½). © 1993, American Chemical Society. All rights reserved.

Duke Scholars

Author Alvin L. Crumbliss Chemistry