Mechanism of Reductive C60Electropolymerization 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, O2•−, induced C60electropolymerization 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 C60in the presence of O2in a mixed organic solvent solution. The C60polymer (C60-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 C60/C60•−couple in the presence of O2was similar to that in its absence, at more negative potentials corresponding to C602−and O2•−formation C602−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 C60at m/zof 720, several additional peaks in the m/zrange of 739−760 appeared, indicating generation of C60O•−and C60O2•−followed by their protonation. Interestingly, the MS spectrum of the product of two-electron reduction of C60revealed several peaks in the m/zrange of 1297−1465. These peaks correspond to the oxygen-containing fullerene protonated dimers, which lose the Cn(n= 1, 2) or C2n(n= 2−5) fragments upon ionization. Apparently, products of the C602−and O2•−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 C60-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 C60-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 C60-O globules, were formed. The electrochemical and viscoelastic properties of the pyr-SWCNTs|C60-O film were unraveled by simultaneously performed CV and piezoelectric microgravimetry (PM) measurements in a blank (TBA)ClO4acetonitrile 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.