Mechanism of Reductive C60 Electropolymerization in the Presence of Dioxygen and Application of the Resulting Fullerene Polymer for Preparation of a Conducting Composite with Single-Wall Carbon Nanotubes

The superoxide anion radical, O-2(center dot-), induced C-60 electropolymerization mechanism was refined by simultaneous cyclic voltammetric (CV) and vis-NIR spectroelectrochemical as well as mass spectrometric (MALDI-TOF) characterization of the one- and two-electron reduction products of C-60 in the presence of O-2 in a mixed organic solvent solution. The C-60 polymer (C-60-O) film was also investigated by Raman spectroscopy and imaged by atomic force microscopy (AFM) both at the early and advanced polymerization stage. While the spectroelectrochemical behavior of the C-60/C-60(center dot-) couple in the presence of O-2 was similar to that in its absence, at more negative potentials corresponding to C-60(2-) and O-2(center dot-) formation C-60(2-) participated in a chemical follow-up reaction resulting in a product lacking any diagnostic absorption band in the vis-NIR range. Although the main peak in the MS spectrum of the one-electron reduction product was that of C-60 at m/z of 720, several additional peaks in the m/z range of 739-760 appeared, indicating generation of C60O.- and C60O.-, followed by their protonation. Interestingly, the MS spectrum of the product of two-electron reduction of C-60 revealed several peaks in the m/z range of 1297-1465. These peaks correspond to the oxygen-containing fullerene protonated dimers, which lose the C-n (n = 1, 2) or C-2n (n = 2-5) fragments upon ionization. Apparently, products of the C-60(2-) and O-2(.-), interaction spontaneously dimerize in the electrode vicinity. Importantly, oxygen is built into the dimeric molecule in the initial stage of electropolymerization. The Raman spectroscopy measurements and AFM surface imaging of the C-60-O film revealed that the first CV cycle resulted in an electrodeposition of dimers. With the increase of the number of CV cycles, the extent of polymerization increased and the polymer structure became highly heterogeneous. Finally, an electrophoretically deposited film of the HiPCO single-wall carbon nanotubes (pyr-SWCNTs) noncovalently surface modified with 1-pyrenebutyric acid was coated by electropolymerization with the C-60-O film under CV conditions to result in a polymer CNT composite material. AFM imaging of this film showed that tangles of the pyr-SWCNTs bundles, coated with the C-60-O globules, were formed. The electrochemical and viscoelastic properties of the pyr-SWCNTsIC60-O film were unraveled by simultaneously performed CV and piezoelectric microgravimetry (PM) measurements in a blank (TBA)CIO4 acetonitrile solution. Specific capacitance of the electrode coated with this composite film was 184 F g(-1) a value comparable to those for other SWNT composite film coated electrodes, suggesting a plausible application of this material in developing supercapacitors.