Synthesis and Redox Characterization of Phosphazene Terpolymers with Pendant Ferrocene Groups

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• 作者：Daniel C. Kraiter ; Patty Wisian-Neilson ; Cuiping Zhang ; Alvin L. Crumbliss
• 刊名：Macromolecules
• 出版年：2012
• 出版时间：May 8, 2012
• 年：2012
• 卷：45
• 期：9
• 页码：3658-3668
• 全文大小：448K
• 年卷期：v.45,no.9(May 8, 2012)
• ISSN：1520-5835

文摘

The synthesis, characterization, and electrochemistry of a series of five ferrocene-containing phosphazene terpolymers derived from the poly(alkyl/arylphosphazene) random copolymer, [(Ph)(Me)PN]_0.6[Me₂PN]_0.4, 5, are described. The new terpolymers, 6 {[(Ph)(Me)PN]_0.6[Me₂PN]_0.4}_x{[(Ph){FcCH(OH)CH₂}PN]_0.6[(Me){FcCH(OH)CH₂}PN]_0.4}_y, where Fc = (畏⁵-C₅H₅)Fe(畏⁵-C₅H₄) (6a, x = 0.50, y = 0.50; 6b, x = 0.60, y = 0.40; 6c, x = 0.65, y = 0.35; 6d, x = 0.70, y = 0.30; and 6e, x = 0.85, y = 0.15), were prepared by deprotonation鈥搒ubstitution reactions and were characterized by NMR spectroscopy, elemental analyses, gel permeation chromatography, and thermal analysis. The redox properties are described by electrochemistry performed in dichloromethane solutions and evaporatively cast films. In solution, cyclic voltammograms of these polymers display a one-electron reversible (螖E_p ca. 60 mV) wave in the range of 433鈥?92 mV (vs Ag/AgCl) combined with adsorption, depending on the degree of substitution with Fc groups. The adsorption of the oxidized polymer on a Pt electrode was established using double potential step chronocoulometry. A mechanism for electron diffusion is discussed in terms of physical diffusion and electron hopping. The apparent electron diffusion coefficient was calculated from a combination method of chronocoulometry and rotating disk voltammetry. The observed diffusion coefficients are larger than those of corresponding polymers that contain a larger number of phenyl side groups and are largely independent of the degree of Fc substitution. A second, less intense wave about 220鈥?50 mV more positive than the main wave was also observed and attributed to the internal oxidation of a secondary alcohol to a ketone group. Reversible electrochemical behavior of surface bound species is also observed for the ferrocene/ferricenium couple in evaporatively cast films of the phosphazene polymers. Cyclic voltammetry and chronoamperometry were used to determine the electrochemical characteristics and charge transport quantities (螕 and CD₀^1/2) of the terpolymer films. These quantities vary with the degree of substitution with Fc groups of the phosphazene terpolymers.