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 (eta 5-C5H4)Fe(eta 5-C5H5) wi th 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 fil ms evaporatively deposited on the electrode surface. The E(1/2) 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 (D-0) for 3-6 were det ermined using a combination of rotating-disk voltammetry and chronocou lometry. A trend of increasing D-0 with increasing degree of ferrocene substitution suggests a dual mode of transport, where both physical d iffusion and electron hopping are occurring. Polymer films were deposi ted by evaporation on Pt and glassy C electrodes, and E(1/2) values we re 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 CH2Cl2. Film-casting parameters were found to influence po lymer swelling and charge-transport numbers ((DoC)-C-1/2), which vary with the degree of ferrocene substitution from 1 X 10(-7) to 5 x 10(-9 ) mol/(cm(2) s(1/2)).